Solar System

Page semi-protected
Listen to this article
From Wikipedia, the free encyclopedia

The Sun. Planets in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Earth's one moon: the Moon. Mars's two moons: Deimos and Phobos. Jupiter's Galilean moons: Io, Callisto, Europa and Ganymede. Saturn's six largest moons: Mimas, Enceladus, Tethys, Dione, Rhea, Titan. Uranus's five largest moons: Miranda, Ariel, Umbriel, Titania, Oberon. Neptune's largest moon: Triton. Dwarf planets in order: Ceres, Pluto, Haumea, Makemake, Quaoar, Orcus, Eris, Gonggong, Sedna.
The Sun, planets, moons and dwarf planets. The asteroid belt and Kuiper belt are not added because the individual asteroids are too small to be shown on the diagram.
Solar System
Age4.568 billion years[a]
Nearest star
Known dwarf planets
Known natural satellites758[5]
Known minor planets1,358,412[6]
Known comets4,591[6]
Planetary system
Star spectral typeG2V
Frost line~5 AU[10]
Semi-major axis of outermost planet30.07 AU[7] (Neptune)
Kuiper cliff50–70 AU[8][9]
Heliopausedetected at 120 AU[11]
Hill sphere~1–3 ly[citation needed]
Orbit about Galactic Center
Invariable-to-galactic plane inclination60.19° (ecliptic)[citation needed]
Distance to
Galactic Center
24,000–28,000 ly
Orbital speed
720,000 km/h (450,000 mi/h)[13]
Orbital period~230 million years[13]

The Solar System[b] is the gravitationally bound system of the Sun and the objects that orbit it.[14] It was formed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is an ordinary main sequence star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere.

The largest objects that orbit the Sun are the eight planets. In order from the Sun, they are four terrestrial planets (Mercury, Venus, Earth and Mars); two gas giants (Jupiter and Saturn); and two ice giants (Uranus and Neptune). All terrestrial planets have solid surfaces. Inversely, all giant planets do not have a definite surface, as they are mainly composed of gases and liquids. Over 99.86% of the Solar System's mass is in the Sun and nearly 90% of the remaining mass is in Jupiter and Saturn.

There is a strong consensus among astronomers[c] that the Solar System has at least eight dwarf planets: Ceres, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, and Sedna. There are a vast number of small Solar System bodies, such as asteroids, comets, centaurs, meteoroids, and interplanetary dust clouds. Some of these bodies are in the asteroid belt (between Mars's and Jupiter's orbit) and the Kuiper belt (just outside Neptune's orbit).[d] Six planets, six dwarf planets, and other bodies have orbiting natural satellites, which are commonly called 'moons'.

The Solar System is constantly flooded by the Sun's charged particles, the solar wind, forming the heliosphere. Around 75–90 astronomical units, the solar wind is halted, resulting in the heliopause. This is the boundary of the Solar System to interstellar space. The outermost region of the Solar System is the theorized Oort cloud, the source for long-period comets, extending 2,000–200,000 astronomical units (0.032–3.2 light-years). The closest star to the Solar System, Proxima Centauri, is 4.25 light-years away. Both stars belong to the Local Group and the Milky Way galaxy.

Formation and evolution

The Solar System formed 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud.[a] This initial cloud was likely several light-years across and probably birthed several stars.[16] As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars.[17]

As the pre-solar nebula[17] collapsed, conservation of angular momentum caused it to rotate faster. The center, where most of the mass collected, became increasingly hotter than the surrounding disc.[16] As the contracting nebula rotated faster, it began to flatten into a protoplanetary disc with a diameter of roughly 200 AU (30 billion km; 19 billion mi)[16] and a hot, dense protostar at the center.[18][19] The planets formed by accretion from this disc,[20] in which dust and gas gravitationally attracted each other, coalescing to form ever larger bodies. Hundreds of protoplanets may have existed in the early Solar System, but they either merged or were destroyed or ejected, leaving the planets, dwarf planets, and leftover minor bodies.[21][22]

Diagram of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed

Due to their higher boiling points, only metals and silicates could exist in solid form in the warm inner Solar System close to the Sun (within the frost line). They would eventually form the rocky planets of Mercury, Venus, Earth, and Mars. Because metallic elements only comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large.[21]

The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid. The ices that formed these planets were more plentiful than the metals and silicates that formed the terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium, the lightest and most abundant elements.[21] Leftover debris that never became planets congregated in regions such as the asteroid belt, Kuiper belt, and Oort cloud.[21]

Within 50 million years, the pressure and density of hydrogen in the center of the protostar became great enough for it to begin thermonuclear fusion.[23] As helium accumulates at its core the Sun is growing brighter;[24] early in its main-sequence life its brightness was 70% that of what it is today.[25] The temperature, reaction rate, pressure, and density increased until hydrostatic equilibrium was achieved: the thermal pressure counterbalancing the force of gravity. At this point, the Sun became a main-sequence star.[26]

Overview of the evolution of the Sun, a G-type main-sequence star. Around 11 billion years after being formed by the Solar System's protoplanetary disk, the Sun will expand to become a red giant; Mercury, Venus and possibly the Earth will be swallowed.

The main-sequence phase, from beginning to end, will last about 10 billion years for the Sun compared to around two billion years for all other subsequent phases of the Sun's pre-remnant life combined.[27] Solar wind from the Sun created the heliosphere and swept away the remaining gas and dust from the protoplanetary disc into interstellar space.[24]

The Solar System is in a relatively stable, slowly evolving state by following isolated, gravitationally bound orbits around the Sun.[28] Although the Solar System has been fairly stable for billions of years, it is technically chaotic, and may eventually be disrupted. There is also a small chance that another star will pass through the Solar System in the next billion years. Although this could destabilize the system and eventually lead millions of years later to expulsion of planets, collisions of planets, or planets hitting the Sun, it would most likely leave the Solar System much as it is today.[29]

The Solar System will remain roughly as it is known today until the hydrogen in the core of the Sun has been entirely converted to helium, which will occur roughly 5 billion years from now. This will mark the end of the Sun's main-sequence life. At that time, the core of the Sun will contract with hydrogen fusion occurring along a shell surrounding the inert helium, and the energy output will be greater than at present. The outer layers of the Sun will expand to roughly 260 times its current diameter, and the Sun will become a red giant. Because of its increased surface area, the surface of the Sun will be cooler (2,600 K (2,330 °C; 4,220 °F) at its coolest) than it is on the main sequence.[27]

The expanding Sun is expected to vaporize Mercury as well as Venus, and render Earth uninhabitable (possibly destroying it as well).[30] Eventually, the core will be hot enough for helium fusion; the Sun will burn helium for a fraction of the time it burned hydrogen in the core. The Sun is not massive enough to commence the fusion of heavier elements, and nuclear reactions in the core will dwindle. Its outer layers will be ejected into space, leaving behind a dense white dwarf, half the original mass of the Sun but only the size of Earth.[27] The ejected outer layers may form a planetary nebula, returning some of the material that formed the Sun—but now enriched with heavier elements like carbon—to the interstellar medium.[31][32]

General characteristics

Astronomers sometimes divide the Solar System structure into searate regions. The inner Solar System includes the Mercury, Venus, Earth, Mars and bodies in the asteroid belt. The outer Solar System includes the Jupiter, Saturn, Uranus, Neptune and bodies in the Kuiper belt.[33] Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune.[34]


The principal component of the Solar System is the Sun, a low-mass star[e] that contains 99.86% of the system's known mass and dominates it gravitationally.[36] The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System (including the four terrestrial planets, the dwarf planets, moons, asteroids, and comets) together comprise less than 0.002% of the Solar System's total mass.[f]

The Sun is composed of roughly 98% hydrogen and helium,[40] as are Jupiter and Saturn.[41][42] A composition gradient exists in the Solar System, created by heat and light pressure from the early Sun; those objects closer to the Sun, which are more affected by heat and light pressure, are composed of elements with high melting points. Objects farther from the Sun are composed largely of materials with lower melting points.[43] The boundary in the Solar System beyond which those volatile substances could coalesce is known as the frost line, and it lies at roughly five times the Earth's distance from the Sun.[10]

The objects of the inner Solar System are composed mostly of rocky materials,[44] such as silicates, iron or nickel.[45] Jupiter and Saturn are composed mainly of gases with extremely low melting points and high vapor pressure, such as hydrogen, helium, and neon.[45] Ices, like water, methane, ammonia, hydrogen sulfide, and carbon dioxide,[44] have melting points of up to a few hundred kelvins.[45] They can be found as ices, liquids, or gases in various places in the Solar System.[45] Icy substances comprise the majority of the satellites of the giant planets, as well as most of Uranus and Neptune (the so-called "ice giants") and the numerous small objects that lie beyond Neptune's orbit.[44][46] Together, gases and ices are referred to as volatiles.[47]


The planets and other large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic. Smaller icy objects such as comets frequently orbit at significantly greater angles to this plane.[48][49] Most of the planets in the Solar System have secondary systems of their own, being orbited by natural satellites called moons. Many of the largest natural satellites are in synchronous rotation, with one face permanently turned toward their parent. The four giant planets have planetary rings, thin bands of tiny particles that orbit them in unison.[50]

As a result of the formation of the Solar System, planets and most other objects orbit the Sun in the same direction that the Sun is rotating. That is, counter-clockwise, as viewed from above Earth's north pole.[51] There are exceptions, such as Halley's Comet.[52] Most of the larger moons orbit their planets in prograde direction, matching the planetary rotation; Neptune's moon Triton is the largest to orbit in the opposite, retrograde manner.[53] Most larger objects rotate around their own axes in the prograde direction relative to their orbit, though the rotation of Venus is retrograde.[54]

To a good first approximation, Kepler's laws of planetary motion describe the orbits of objects around the Sun.[55]: 433–437  These laws stipulate that each object travels along an ellipse with the Sun at one focus, which causes the body's distance from the Sun to vary over the course of its year. A body's closest approach to the Sun is called its perihelion, whereas its most distant point from the Sun is called its aphelion.[56]: 9-6  With the exception of Mercury, the orbits of the planets are nearly circular, but many comets, asteroids, and Kuiper belt objects follow highly elliptical orbits. Kepler's laws only account for the influence of the Sun's gravity upon an orbiting body, not the gravitational pulls of different bodies upon each other. On a human time scale, these additional perturbations can be accounted for using numerical models,[56]: 9-6  but the planetary system can change chaotically over billions of years.[57]

The angular momentum of the Solar System is a measure of the total amount of orbital and rotational momentum possessed by all its moving components.[58] Although the Sun dominates the system by mass, it accounts for only about 2% of the angular momentum.[59][60] The planets, dominated by Jupiter, account for most of the rest of the angular momentum due to the combination of their mass, orbit, and distance from the Sun, with a possibly significant contribution from comets.[59]

Distances and scales

To-scale diagram of distance between planets, with the white bar showing orbital variations. The size of the planets is not to scale.

The astronomical unit [AU] (150,000,000 km; 93,000,000 mi) would be the distance from the Earth to the Sun if the planet's orbit were perfectly circular.[61] For comparison, the radius of the Sun is 0.0047 AU (700,000 km; 400,000 mi).[62] Thus, the Sun occupies 0.00001% (10−5 %) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly one millionth (10−6) that of the Sun. Jupiter, the largest planet, is 5.2 astronomical units (780,000,000 km; 480,000,000 mi) from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune, is 30 AU (4.5×109 km; 2.8×109 mi) from the Sun.[42][63]

With a few exceptions, the farther a planet or belt is from the Sun, the larger the distance between its orbit and the orbit of the next nearest object to the Sun. For example, Venus is approximately 0.33 AU farther out from the Sun than Mercury, whereas Saturn is 4.3 AU out from Jupiter, and Neptune lies 10.5 AU out from Uranus. Attempts have been made to determine a relationship between these orbital distances, like the Titius–Bode law[64] and Johannes Kepler's model based on the Platonic solids,[65] but ongoing discoveries have invalidated these hypotheses.[66]

Some Solar System models attempt to convey the relative scales involved in the Solar System in human terms. Some are small in scale (and may be mechanical—called orreries)—whereas others extend across cities or regional areas.[67] The largest such scale model, the Sweden Solar System, uses the 110-metre (361 ft) Avicii Arena in Stockholm as its substitute Sun, and, following the scale, Jupiter is a 7.5-metre (25-foot) sphere at Stockholm Arlanda Airport, 40 km (25 mi) away, whereas the farthest current object, Sedna, is a 10 cm (4 in) sphere in Luleå, 912 km (567 mi) away.[68][69]

If the Sun–Neptune distance is scaled to 100 metres (330 ft), then the Sun would be about 3 cm (1.2 in) in diameter (roughly two-thirds the diameter of a golf ball), the giant planets would be all smaller than about 3 mm (0.12 in), and Earth's diameter along with that of the other terrestrial planets would be smaller than a flea (0.3 mm or 0.012 in) at this scale.[70]

Interplanetary environment

Coronal mass ejections play a dominant role in the Solar System's environment and space weather in general.

The outermost layer of the Solar atmosphere is the heliosphere, which permeates much of the Solar planetary system. Along with light, the Sun radiates a continuous stream of charged particles (a plasma) called the solar wind. This stream of particles spreads outwards at speeds from 900,000 kilometres per hour (560,000 mph) to 2,880,000 kilometres per hour (1,790,000 mph),[71] filling the vacuum between the bodies of the Solar System. The result is a thin, dusty atmosphere, called the interplanetary medium, which extends to at least 100 AU (15 billion km; 9.3 billion mi). Beyond the heliosphere, large objects remain gravitationally bound to the sun, but the flow of matter in the interstellar medium homogenizes the distribution of micro-scale objects (see § Farthest regions).[72]

The interplanetary medium is home to at least two disc-like regions of cosmic dust. The first, the zodiacal dust cloud, lies in the inner Solar System and causes the zodiacal light. It may have been formed by collisions within the asteroid belt brought on by gravitational interactions with the planets; a more recent proposed origin is the planet Mars.[73] The second dust cloud extends from about 10 AU (1.5 billion km; 930 million mi) to about 40 AU (6.0 billion km; 3.7 billion mi), and was probably created by collisions within the Kuiper belt.[74][75]

Activity on the Sun's surface, such as solar flares and coronal mass ejections, disturbs the heliosphere, creating space weather and causing geomagnetic storms.[76] Coronal mass ejections and similar events blow a magnetic field and huge quantities of material from the surface of the Sun. The interaction of this magnetic field and material with Earth's magnetic field funnels charged particles into Earth's upper atmosphere, where its interactions create aurorae seen near the magnetic poles.[77] The largest stable structure within the heliosphere is the heliospheric current sheet, a spiral form created by the actions of the Sun's rotating magnetic field on the interplanetary medium.[78][79]


Besides solar energy, the primary characteristic of the Solar System enabling the presence of life is the heliosphere and planetary magnetic fields (for those planets that have them). These magnetic fields partially shield the Solar System from high-energy interstellar particles called cosmic rays. The density of cosmic rays in the interstellar medium and the strength of the Sun's magnetic field change on very long timescales, so the level of cosmic-ray penetration in the Solar System varies, though by how much is unknown.[80]

The zone of habitability of the Solar System is conventionally located in the inner Solar System, where planetary surface or atmospheric temperatures admit the possibility of liquid water.[81] Habitability might also be possible in subsurface oceans of various outer Solar System moons.[82]

Comparison with extrasolar systems

Comparison between the habitable zones of the Solar System and Gliese 581 (planet d was later found to not exist). The habitable zone is highly dependent on parent star's luminosity.

Compared to many extrasolar systems, the Solar System stands out in lacking planets interior to the orbit of Mercury.[83][84] The known Solar System also lacks super-Earths, planets between one and ten times as massive as the Earth,[83] although the hypothetical Planet Nine, if it does exist, could be a super-Earth orbiting in the edge of the Solar System.[85]

Uncommonly, it has only small terrestrial and large gas giants; elsewhere planets of intermediate size are typical—both rocky and gas—so there is no "gap" as seen between the size of Earth and of Neptune (with a radius 3.8 times as large). As many of these super-Earths are closer to their respective stars than Mercury is to the Sun. A hypothesis has arisen that all planetary systems start with many close-in planets, and that typically a sequence of their collisions causes consolidation of mass into few larger planets, but in case of the Solar System the collisions caused their destruction and ejection.[83][86]

The orbits of Solar System planets are nearly circular. Compared to other systems, they have smaller orbital eccentricity.[83] Although there are attempts to explain it partly with a bias in the radial-velocity detection method and partly with long interactions of a quite high number of planets, the exact causes remain undetermined.[83][87]


The Sun in true white color

The Sun is the Solar System's star and by far its most massive component. Its large mass (332,900 Earth masses),[88] which comprises 99.86% of all the mass in the Solar System,[89] produces temperatures and densities in its core high enough to sustain nuclear fusion of hydrogen into helium.[90] This releases an enormous amount of energy, mostly radiated into space as electromagnetic radiation peaking in visible light.[91][92]

Because the Sun fuses hydrogen into helium at its core, it is a main-sequence star. More specifically, it is a G2-type main-sequence star, where the type designation refers to its effective temperature. Hotter main-sequence stars are more luminous but shorter lived. The Sun's temperature is intermediate between that of the hottest stars and that of the coolest stars. Stars brighter and hotter than the Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs, make up about 75% of the stars in the Milky Way.[93]

The Sun is a population I star; it has a higher abundance of elements heavier than hydrogen and helium ("metals" in astronomical parlance) than the older population II stars.[94] Elements heavier than hydrogen and helium were formed in the cores of ancient and exploding stars, so the first generation of stars had to die before the universe could be enriched with these atoms. The oldest stars contain few metals, whereas stars born later have more. This higher metallicity is thought to have been crucial to the Sun's development of a planetary system because the planets form from the accretion of "metals".[95]

Inner Solar System

The inner Solar System is the region comprising the terrestrial planets and the asteroid belt.[96] Composed mainly of silicates and metals,[97] the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn. This region is also within the frost line, which is a little less than 5 AU (750 million km; 460 million mi) from the Sun.[48]

Notably, no vulcanoids, asteroids between Mercury and the Sun, have been discovered.[98][99] As of 2024, one asteroid is discovered to orbit within Venus's orbit, which is 594913 ꞌAylóꞌchaxnim.[100] Asteroids that orbit within Earth's orbit are called Atira asteroids.[101]

Inner planets

The four terrestrial or inner planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of refractory minerals such as silicates—which form their crusts and mantles—and metals such as iron and nickel which form their cores. Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features, such as rift valleys and volcanoes. The term inner planet should not be confused with inferior planet, which designates those planets that are closer to the Sun than Earth (i.e. Mercury and Venus).[102]

  • Mercury (0.31–0.59 astronomical units or AU from the Sun)[103] is the closest planet to the Sun. It is the smallest planet in the Solar System. The dominant geological features are impact craters and ejecta blankets, which are evidences of early volcanic activity. Its surface also has various rupes, lobed ridges that were probably produced by surface cooling contraction early in the planet's history.[104] Mercury has a very tenuous atmosphere, consisting of solar-wind particles and ejected atoms.[105] Its relatively large iron core and thin mantle have not yet been adequately explained. Mercury has no natural satellites.
  • Venus (0.72–0.73 AU)[103] is much drier than Earth and its atmosphere is ninety times as dense. Venus has no natural satellites. It has a thick silicate mantle around an iron core, a substantial atmosphere, and evidence of past geological activity. Venus is the hottest planet, with surface temperatures over 400 °C (752 °F), mainly due to the amount of greenhouse gases in the atmosphere.[106] The planet has no magnetic field that would prevent the depletion of its substantial atmosphere, which suggests that its atmosphere is being replenished by volcanic eruptions.[107] A relatively young planetary surface displays extensive evidence of volcanic activity, but is devoid of plate tectonics.[108]
  • Earth (0.98–1.02 AU)[103] is the largest and densest of the inner planets, the only one known to have current geological activity, and the only place in the universe where life is known to exist.[109] Its liquid hydrosphere is unique among the terrestrial planets, and it is the only planet where plate tectonics has been observed.[110] Earth's atmosphere is radically different from those of the other planets, having been altered by the presence of life to contain 21% free oxygen.[111][112] The planetary magnetosphere shields the surface from solar and cosmic radiation, limiting atmospheric stripping and maintaining habitability.[113] It has one natural satellite, the Moon.[114]
  • Mars (1.38–1.67 AU)[103] has an atmosphere of mostly carbon dioxide with a surface pressure of 0.6% of that of Earth. This is sufficient to support weather phenomena.[115] Its surface, peppered with volcanoes, such as Olympus Mons, and rift valleys, such as Valles Marineris, shows geological activity that may have persisted until as recently as 2 million years ago.[116] Its red color comes from iron oxide in its soil,[117] while the polar regions show white ice caps consisting largely of water.[118] Mars has two tiny natural satellites (Deimos and Phobos) thought to be either captured asteroids,[119] or ejected debris from a massive impact early in Mars's history.[120]

Asteroid belt

Linear map of the inner Solar System, showing many asteroid populations

Asteroids except for the largest, Ceres, are classified as small Solar System bodies and are composed mainly of carbonaceous, refractory rocky and metallic minerals, with some ice.[121][122] They range from a few metres to hundreds of kilometres in size. Asteroids smaller than one meter are usually called meteoroids and micrometeoroids (grain-sized), with the exact division between the two categories being debated over the years.[123] As of 2017, the IAU designates asteroids having a diameter between about 30 micrometres and 1 metre as micrometeoroids, and terms smaller particles "dust".[124]

The asteroid belt occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU (340 and 490 million km; 210 and 310 million mi) from the Sun. It is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter.[125] The asteroid belt contains tens of thousands, possibly millions, of objects over one kilometre in diameter.[126] Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth.[39] The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident.[127]

Below are the descriptions of three largest objects in the asteroid belt:

  • Ceres (2.55–2.98 AU) is the largest asteroid, a protoplanet, and a dwarf planet. It has a diameter of slightly under 1,000 km (620 mi) and a mass large enough for its own gravity to pull it into a spherical shape. Ceres was considered a planet when it was discovered in 1801, but as further observations revealed additional asteroids, it became common to consider it as one of the minor rather than major planets.[128] It was then reclassified again as a dwarf planet in 2006 when the IAU definition of planet was established.[129]: 218 
  • Pallas (2.13–3.41 AU) and Vesta (2.15–2.57 AU) are the largest asteroids in the asteroid belt, after Ceres. They are the other two protoplanets that survive more or less intact. At about 520 km (320 mi) in diameter, they were large enough to have developed planetary geology in the past, but both have suffered large impacts and been battered out of being round.[130][131][132] Fragments from impacts upon these two bodies survive elsewhere in the asteroid belt, as the Pallas family and Vesta family. Both were considered planets upon their discoveries in 1802 and 1807 respectively, and like Ceres, eventually considered minor planets with the discovery of more asteroids. Some authors today have begun to consider Pallas and Vesta as planets again, along with Ceres, under geophysical definitions of the term.[133]

Asteroids are divided into asteroid groups and families based on their orbital characteristics. Kirkwood gaps are sharp dips in the distribution of asteroid orbits that correspond to orbital resonances with Jupiter.[134] Asteroid moons are asteroids that orbit larger asteroids. They are not as clearly distinguished as planetary moons, sometimes being almost as large as their partners (e.g. that of 90 Antiope). The asteroid belt includes main-belt comets, which may have been the source of Earth's water.[135]

Jupiter trojans are located in either of Jupiter's L4 or L5 points (gravitationally stable regions leading and trailing a planet in its orbit); the term trojan is also used for small bodies in any other planetary or satellite Lagrange point. Hilda asteroids are in a 2:3 resonance with Jupiter; that is, they go around the Sun three times for every two Jupiter orbits.[136] The inner Solar System contains near-Earth asteroids, many of which cross the orbits of the inner planets.[137] Some of them are potentially hazardous objects.[138]

Outer Solar System

The outer region of the Solar System is home to the giant planets and their large moons. The centaurs and many short-period comets also orbit in this region. Due to their greater distance from the Sun, the solid objects in the outer Solar System contain a higher proportion of volatiles, such as water, ammonia, and methane than those of the inner Solar System because the lower temperatures allow these compounds to remain solid, without significant rates of sublimation.[21]

Outer planets

The four outer planets, also called giant planets or Jovian planets, collectively make up 99% of the mass known to orbit the Sun.[f] Jupiter and Saturn are together more than 400 times the mass of Earth and consist overwhelmingly of the gases hydrogen and helium, hence their designation as gas giants.[139] Uranus and Neptune are far less massive—less than 20 Earth masses each—and are composed primarily of ice. For these reasons, some astronomers suggest they belong in their own category, ice giants.[140] All four giant planets have rings, although only Saturn's ring system is easily observed from Earth. The term superior planet designates planets outside Earth's orbit and thus includes both the outer planets and Mars.[102]

The ring–moon systems of Jupiter, Saturn, and Uranus are like miniature versions of the Solar System; that of Neptune is significantly different, having been disrupted by the capture of its largest moon Triton.[141]

  • Jupiter (4.95–5.46 AU)[103] at 318 Earth masses, is 2.5 times the mass of all the other planets put together. It is composed largely of hydrogen and helium. Jupiter's strong internal heat creates semi-permanent features in its atmosphere, such as cloud bands and the Great Red Spot. The planet possesses a 4.2–14 Gauss strength magnetosphere that spans 22–29 million km.[142] Jupiter has 95 known satellites. The four largest, Ganymede, Callisto, Io, and Europa, are called the Galilean moons: they show similarities to the terrestrial planets, such as volcanism and internal heating.[143] Ganymede, the largest satellite in the Solar System, is larger than Mercury; Callisto is almost as large.[144]
  • Saturn (9.08–10.1 AU),[103] distinguished by its extensive ring system, has several similarities to Jupiter, such as its atmospheric composition and magnetosphere. Although Saturn has 60% of Jupiter's volume, it is less than a third as massive, at 95 Earth masses. Saturn is the only planet of the Solar System that is less dense than water. The rings of Saturn are made up of small ice and rock particles.[145] Saturn has 145 confirmed satellites composed largely of ice. Two of these, Titan and Enceladus, show signs of geological activity;[146] they, as well as five other Saturnian moons (Iapetus, Rhea, Dione, Tethys, and Mimas), are large enough to be round. Titan, the second-largest moon in the Solar System, is bigger than Mercury and the only satellite in the Solar System to have a substantial atmosphere.[147][148]
  • Uranus (18.3–20.1 AU),[103] at 14 Earth masses, has the lowest mass of the outer planets. Uniquely among the planets, it orbits the Sun on its side; its axial tilt is over ninety degrees to the ecliptic. This gives the planet extreme seasonal variation as each pole points toward and then away from the Sun.[149] It has a much colder core than the other giant planets and radiates very little heat into space.[150] As a consequence, it has the coldest planetary atmosphere in the Solar System.[151] Uranus has 27 known satellites, the largest ones being Titania, Oberon, Umbriel, Ariel, and Miranda.[152] Like the other giant planets, it possesses a ring system and magnetosphere.[153]
  • Neptune (29.9–30.5 AU),[103] though slightly smaller than Uranus, is more massive (17 Earth masses). It radiates more internal heat than Uranus, but not as much as Jupiter or Saturn.[154] Neptune has 14 known satellites. The largest, Triton, is geologically active, with geysers of liquid nitrogen.[155] Triton is the only large satellite with a retrograde orbit, which indicates that it did not form with Neptune, but was probably captured from the Kuiper belt.[156] Neptune is accompanied in its orbit by several minor planets, termed Neptune trojans, that either lead or trail the planet by about one-sixth of the way around the Sun, positions known as Lagrange points.[157]


The centaurs are icy comet-like bodies whose semi-major axes is greater than Jupiter's and less than Neptune's (between 5.5 and 30 AU). These are former Kuiper belt and scattered disc objects that were gravitationally perturbed closer to the Sun by the outer planets, and are expected to become comets or get ejected out of the Solar System.[38] While most centaurs are inactive and asteroid-like, some exhibit clear cometary activity, such as the first centaur discovered, 2060 Chiron, which has been classified as a comet (95P) because it develops a coma just as comets do when they approach the Sun.[158] The largest known centaur, 10199 Chariklo, has a diameter of about 250 km (160 mi) and is one of the only few minor planets known to possess a ring system.[159][160]


Comet Hale–Bopp seen in 1997

Comets are small Solar System bodies, typically only a few kilometres across, composed largely of volatile ices. They have highly eccentric orbits, generally a perihelion within the orbits of the inner planets and an aphelion far beyond Pluto. When a comet enters the inner Solar System, its proximity to the Sun causes its icy surface to sublimate and ionise, creating a coma: a long tail of gas and dust often visible to the naked eye.[161]

Short-period comets have orbits lasting less than two hundred years. Long-period comets have orbits lasting thousands of years. Short-period comets are thought to originate in the Kuiper belt, whereas long-period comets, such as Hale–Bopp, are thought to originate in the Oort cloud. Many comet groups, such as the Kreutz sungrazers, formed from the breakup of a single parent.[162] Some comets with hyperbolic orbits may originate outside the Solar System, but determining their precise orbits is difficult.[163] Old comets whose volatiles have mostly been driven out by solar warming are often categorised as asteroids.[164]

Trans-Neptunian region

Beyond the orbit of Neptune lies the area of the "trans-Neptunian region", with the doughnut-shaped Kuiper belt, home of Pluto and several other dwarf planets, and an overlapping disc of scattered objects, which is tilted toward the plane of the Solar System and reaches much further out than the Kuiper belt. The entire region is still largely unexplored. It appears to consist overwhelmingly of many thousands of small worlds—the largest having a diameter only a fifth that of Earth and a mass far smaller than that of the Moon—composed mainly of rock and ice. This region is sometimes described as the "third zone of the Solar System", enclosing the inner and the outer Solar System.[165]

Kuiper belt

Orbit classification of Kuiper belt objects. Some clusters that is subjected to orbital resonance are also marked.

The Kuiper belt is a great ring of debris similar to the asteroid belt, but consisting mainly of objects composed primarily of ice.[166] It extends between 30 and 50 AU from the Sun. It is composed mainly of small Solar System bodies, although the largest few are probably large enough to be dwarf planets.[167] There are estimated to be over 100,000 Kuiper belt objects with a diameter greater than 50 km (30 mi), but the total mass of the Kuiper belt is thought to be only a tenth or even a hundredth the mass of Earth.[38] Many Kuiper belt objects have satellites,[168] and most have orbits that are substantially inclined (~10°) to the plane of the ecliptic.[169]

The Kuiper belt can be roughly divided into the "classical" belt and the resonant trans-Neptunian objects.[166] The latter have orbits whose periods are in a simple ratio to that of Neptune: for example, going around the Sun twice for every three times that Neptune does, or once for every two. The classical belt consists of objects having no resonance with Neptune, and extends from roughly 39.4 to 47.7 AU.[170] Members of the classical Kuiper belt are sometimes called "cubewanos", after the first of their kind to be discovered, originally designated 1992 QB1; they are still in near primordial, low-eccentricity orbits.[171]

Currently, there are four dwarf planets in the Kuiper belt that have strong consensus among astronomers.[167][172] Many dwarf planet candidates are also being considered, pending further data for verification.[173]

  • Pluto (29.7–49.3 AU) is the largest known object in the Kuiper belt. When discovered in 1930, it was considered to be the ninth planet; this changed in 2006 with the adoption of a formal definition of planet. Pluto has a relatively eccentric orbit, inclined 17 degrees to the ecliptic plane. Pluto has a 2:3 resonance with Neptune, meaning that Pluto orbits twice round the Sun for every three Neptunian orbits. Kuiper belt objects whose orbits share this resonance are called plutinos.[174] Charon, the largest of Pluto's moons, is sometimes described as part of a binary system with Pluto, as the two bodies orbit a barycenter of gravity above their surfaces (i.e. they appear to "orbit each other"). Beyond Charon, four much smaller moons, Styx, Nix, Kerberos, and Hydra, orbit Pluto.[175]
  • Makemake (38.1–52.8 AU), although smaller than Pluto, is the largest known object in the classical Kuiper belt (that is, a Kuiper belt object not in a confirmed resonance with Neptune). Makemake is the brightest object in the Kuiper belt after Pluto. Discovered in 2005, it was officially named in 2009.[176] Its orbit is far more inclined than Pluto's, at 29°.[177] It has one known moon.[178]
  • Haumea (34.6–51.6 AU) is in an orbit similar to Makemake, except that it is in a temporary 7:12 orbital resonance with Neptune.[179] Like Makemake, it was discovered in 2005.[180] Uniquely among the dwarf planets, Haumea possesses a ring system, two known moons named Hiʻiaka and Namaka, and rotates so quickly (once every 3.9 hours) that it is stretched into an ellipsoid. It is part of a collisional family of Kuiper belt objects that share similar orbits, which suggests a giant collision took place on Haumea and ejected its fragments into space billions of years ago.[181]
  • Quaoar (41.9–45.5 AU) is the second-largest known object in the classical Kuiper belt, after Makemake. Its orbit is significantly less eccentric and inclined than those of Makemake or Haumea.[179] It possesses a ring system and one known moon, Weywot.[182]
  • Orcus (30.3–48.1 AU), another Kuiper belt object and the largest that is probably not a dwarf planet: it is in the same 2:3 orbital resonance with Neptune as Pluto, and is the largest such object after Pluto itself.[179] Its eccentricity and inclination are similar to Pluto's, but its perihelion lies about 120° from that of Pluto. Thus, the phase of Orcus's orbit is opposite to Pluto's: Orcus is at aphelion (most recently in 2019) around when Pluto is at perihelion (most recently in 1989) and vice versa.[183] For this reason, it has been called the anti-Pluto.[184][185] It has one known moon, Vanth.[186]

Scattered disc

The orbital eccentricities and inclinations of the scattered disc population compared to the classical and resonant Kuiper belt objects

The scattered disc, which overlaps the Kuiper belt but extends out to near 500 AU, is thought to be the source of short-period comets. Scattered-disc objects are believed to have been perturbed into erratic orbits by the gravitational influence of Neptune's early outward migration. Most scattered disc objects (SDOs) have perihelia within the Kuiper belt but aphelia far beyond it (some more than 150 AU from the Sun). SDOs' orbits can also be inclined up to 46.8° from the ecliptic plane.[187] Some astronomers consider the scattered disc to be merely another region of the Kuiper belt and describe scattered-disc objects as "scattered Kuiper belt objects".[188] Some astronomers also classify centaurs as inward-scattered Kuiper belt objects along with the outward-scattered residents of the scattered disc.[189]

Currently, there are two dwarf planets that has strong consensus among astronomers:

  • Eris (38.3–97.5 AU) is the largest known scattered disc object, and caused a debate about what constitutes a planet, because it is 25% more massive than Pluto[190] and about the same diameter. It is the most massive of the known dwarf planets. It has one known moon, Dysnomia. Like Pluto, its orbit is highly eccentric, with a perihelion of 38.2 AU (roughly Pluto's distance from the Sun) and an aphelion of 97.6 AU, and steeply inclined to the ecliptic plane at an angle of 44°.[191]
  • Gonggong (33.8–101.2 AU) is another dwarf planet in a comparable orbit to Eris, except that it is in a 3:10 resonance with Neptune.[192] It has one known moon, Xiangliu.[193]

Farthest regions

The point at which the Solar System ends and interstellar space begins is not precisely defined because its outer boundaries are shaped by two forces: the solar wind and the Sun's gravity. The limit of the solar wind's influence is roughly four times Pluto's distance from the Sun; this heliopause, the outer boundary of the heliosphere, is considered the beginning of the interstellar medium.[72] The Sun's Hill sphere, the effective range of its gravitational dominance, is thought to extend up to a thousand times farther and encompasses the hypothetical Oort cloud.[194]

The Solar System within the interstellar medium, with the different regions and their distances on a steped horizontal distance scale (object's size not to scale).

Edge of the heliosphere

Diagram of the Sun's magnetosphere and helioshealth

The Sun's stellar-wind bubble, the heliosphere, a region of space dominated by the Sun, has its boundary at the termination shock, which is roughly 80–100 AU from the Sun upwind of the interstellar medium and roughly 200 AU from the Sun downwind.[195] Here the solar wind collides with the interstellar medium[196] and dramatically slows, condenses and becomes more turbulent,[195] forming a great oval structure known as the heliosheath. This structure has been theorized to look and behave very much like a comet's tail, extending outward for a further 40 AU on the upwind side but tailing many times that distance downwind.[197] Evidence from the Cassini and Interstellar Boundary Explorer spacecraft has suggested that it is forced into a bubble shape by the constraining action of the interstellar magnetic field,[198][199] but the actual shape remains unknown.[200]

The outer boundary of the heliosphere, the heliopause, is the point at which the solar wind finally terminates and is the beginning of interstellar space.[72] Voyager 1 and Voyager 2 passed the termination shock and entered the heliosheath at 94 and 84 AU from the Sun, respectively.[201][202] Voyager 1 was reported to have crossed the heliopause in August 2012, and Voyager 2 in December 2018.[203][204]

The shape and form of the outer edge of the heliosphere is likely affected by the fluid dynamics of interactions with the interstellar medium as well as solar magnetic fields prevailing to the south, e.g. it is bluntly shaped with the northern hemisphere extending 9 AU farther than the southern hemisphere.[195] Beyond the heliopause, at around 230 AU, lies the bow shock: a plasma "wake" left by the Sun as it travels through the Milky Way.[205]

Detached objects

The detached object Sedna and its orbit within the Solar System

Sedna (with an average orbit of 520 AU from the Sun) is a large, reddish object with a gigantic, highly elliptical orbit that takes it from about 76 AU at perihelion to 940 AU at aphelion and takes 11,400 years to complete. Mike Brown, who discovered the object in 2003, asserts that it cannot be part of the scattered disc or the Kuiper belt because its perihelion is too distant to have been affected by Neptune's migration. He and other astronomers consider it to be the first in an entirely new population, sometimes termed "distant detached objects" (DDOs), which also may include the object 2000 CR105, which has a perihelion of 45 AU, an aphelion of 415 AU, and an orbital period of 3,420 years.[206]

Brown terms this population the "inner Oort cloud" because it may have formed through a similar process, although it is far closer to the Sun.[207] Sedna is very likely a dwarf planet, though its shape has yet to be determined. The second unequivocally detached object, with a perihelion farther than Sedna's at roughly 81 AU, is 2012 VP113, discovered in 2012. Its aphelion is only about half that of Sedna's, at 458 AU.[208][209]


The Sun's gravitational field is estimated to dominate the gravitational forces of surrounding stars out to about two light-years (125,000 AU). Lower estimates for the radius of the Oort cloud, by contrast, do not place it farther than 50,000 AU.[210] Most of the mass is orbiting in the region between 3,000 and 100,000 AU.[211] The furthest known objects, such as Comet West, have aphelia around 70,000 AU from the Sun.[212]

Much of the Solar System is still unknown. Areas beyond thousands of AU away is still virtually unmapped and learning about this region of space is difficult. Study in this region depends upon inferences from those few objects whose orbits happen to be perturbed such that they fall closer to the Sun, and even then, detecting these objects has often been possible only when they happened to become bright enough to register as comets.[213] Many objects may yet be discovered in the Solar System's uncharted regions.[214]

One of these objects might be the Oort cloud, a theorized spherical cloud of up to a trillion icy objects that is thought to be the source for all long-period comets.[215][216] No direct observation of the Oort cloud is possible with present imaging technology.[217] It is theorized to surround the Solar System at roughly 50,000 AU (around 1 light-year (ly)) from the Sun and possibly to as far as 100,000 AU (1.87 ly). The Oort cloud is thought to be composed of comets that were ejected from the inner Solar System by gravitational interactions with the outer planets. Oort cloud objects move very slowly, and can be perturbed by infrequent events, such as collisions, the gravitational effects of a passing star, or the galactic tide, the tidal force exerted by the Milky Way.[215][216]

As of the early 2020s, a few astronomers hypothesized that Planet Nine (a planet beyond Neptune) might exist, based on the orbit of extreme trans-Neptunian objects. Their closest approaches to the Sun are mostly clustered around one sector and their orbits are similarly tilted, suggesting that a large planet might be influencing their orbit over millions of years.[218][219] However, this observation might be credited to observational biases or just sheer coincidence.[220]


Celestial neighborhood

Diagram of the Local Interstellar Cloud, the G-Cloud and surrounding stars. As of 2022, the precise location of the Solar System in the clouds is an open question in astronomy.[221]

The Solar System is surrounded by the Local Interstellar Cloud, although it is not clear if it is embedded in the Local Interstellar Cloud or if it lies just outside the cloud's edge.[222][223] Multiple other interstellar clouds also exist in the region within 300 light-years of the Sun, known as the Local Bubble.[223] The latter feature is an hourglass-shaped cavity or superbubble in the interstellar medium roughly 300 light-years across. The bubble is suffused with high-temperature plasma, suggesting that it may be the product of several recent supernovae.[224]

The Local Bubble is a small superbubble compared to the neighboring wider Radcliffe Wave and Split linear structures (formerly Gould Belt), each of which are some thousands of light-years in length.[225] All these structures are part of the Orion Arm, which contains most of the stars in the Milky Way that are visible to the unaided eye. The density of all matter in the local neighborhood is 0.097±0.013 M·pc−3.[226]

Within ten light-years of the Sun there are relatively few stars, the closest being the triple star system Alpha Centauri, which is about 4.4 light-years away and may be in the Local Bubble's G-Cloud.[227] Alpha Centauri A and B are a closely tied pair of Sun-like stars, whereas the closest star to Earth, the small red dwarf Proxima Centauri, orbits the pair at a distance of 0.2 light-year. In 2016, a potentially habitable exoplanet was found to be orbiting Proxima Centauri, called Proxima Centauri b, the closest confirmed exoplanet to the Sun.[228]

The next closest known fusors to the Sun are the red dwarfs Barnard's Star (at 5.9 ly), Wolf 359 (7.8 ly), and Lalande 21185 (8.3 ly).[229] The nearest brown dwarfs belong to the binary Luhman 16 system (6.6 ly), and the closest known rogue or free-floating planetary-mass object at less than 10 Jupiter masses is the sub-brown dwarf WISE 0855−0714 (7.4 ly).[230]

Just beyond at 8.6 ly lies Sirius, the brightest star in Earth's night sky, with roughly twice the Sun's mass, orbited by the closest white dwarf to Earth, Sirius B. Other stars within ten light-years are the binary red-dwarf system Gliese 65 (8.7 ly) and the solitary red dwarf Ross 154 (9.7 ly).[231][232] The closest solitary Sun-like star to the Solar System is Tau Ceti at 11.9 light-years. It has roughly 80% of the Sun's mass but only about half of its luminosity.[233]

The nearest and unaided-visible group of stars beyond the immediate celestial neighborhood is the Ursa Major moving group at roughly 80 light-years, which is within the Local Bubble, like the nearest as well as unaided-visible star cluster the Hyades, which lie at its edge. The closest star-forming regions are the Corona Australis Molecular Cloud, the Rho Ophiuchi cloud complex and the Taurus molecular cloud; the latter lies just beyond the Local Bubble and is part of the Radcliffe wave.[234]

Galactic position and orbit

Diagram of the Milky Way, with galactic features and the relative position of the Solar System labelled.

The Solar System is located in the Milky Way, a barred spiral galaxy with a diameter of about 100,000 light-years containing more than 100 billion stars.[235] The Sun is part of one of the Milky Way's outer spiral arms, known as the Orion–Cygnus Arm or Local Spur.[236][237]

Its speed around the center of the Milky Way is about 220 km/s, so that it completes one revolution every 240 million years.[235] This revolution is known as the Solar System's galactic year.[238] The solar apex, the direction of the Sun's path through interstellar space, is near the constellation Hercules in the direction of the current location of the bright star Vega.[239] The plane of the ecliptic lies at an angle of about 60° to the galactic plane.[g]

The Solar System's location in the Milky Way is a factor in the evolutionary history of life on Earth. Spiral arms are home to a far larger concentration of supernovae, gravitational instabilities, and radiation that could disrupt the Solar System, but since Earth stays in the Local Spur and therefore does not pass frequently through spiral arms, this has given Earth long periods of stability for life to evolve.[241] However, the changing position of the Solar System relative to other parts of the Milky Way could explain periodic extinction events on Earth, according to the Shiva hypothesis or related hypotheses, but this remains controversial.[242][243]

The Sun orbits close to circular the Galactic Center (where the supermassive black hole Sagittarius A* resides) at a distance of 26,660 light-years,[244] orbiting at roughly the same speed as that of the spiral arms.[241] Near the center, gravitational tugs from nearby stars could perturb bodies in the Oort cloud and send many comets into the inner Solar System, producing collisions with potentially catastrophic implications for life on Earth. The intense radiation of the Galactic Center could also interfere with the development of complex life.[241]

Stellar flybys that pass within 0.8 light-years of the Sun occur roughly once every 100,000 years. The closest well-measured approach was Scholz's Star, which approached to ~50,000AU of the Sun some ~70 thousands years ago, likely passing through the outer Oort cloud.[245] There is a 1% chance every billion years that a star will pass within 100 AU of the Sun, potentially disrupting the Solar System.[246]

Humanity's perspective

The motion of 'lights' moving across the sky is the basis of the classical definition of planets: wandering stars.

Humanity's knowledge of the Solar System has grown incrementally over the centuries. Up to the Late Middle AgesRenaissance, astronomers from Europe to India believed Earth to be stationary at the center of the universe[247] and categorically different from the divine or ethereal objects that moved through the sky. Although the Greek philosopher Aristarchus of Samos had speculated on a heliocentric reordering of the cosmos, Nicolaus Copernicus was the first person known to have developed a mathematically predictive heliocentric system.[248][249]

Heliocentrism did not triumph immediately over geocentrism, but the work of Copernicus had its champions, notably Johannes Kepler. Using a heliocentric model that improved upon Copernicus by allowing orbits to be elliptical, and the precise observational data of Tycho Brahe, Kepler produced the Rudolphine Tables, which enabled accurate computations of the positions of the then-known planets. Pierre Gassendi used them to predict a transit of Mercury in 1631, and Jeremiah Horrocks did the same for a transit of Venus in 1639. This provided a strong vindication of heliocentrism and Kepler's elliptical orbits.[250][251]

In the 17th century, Galileo publicized the use of the telescope in astronomy; he and Simon Marius independently discovered that Jupiter had four satellites in orbit around it.[252] Christiaan Huygens followed on from these observations by discovering Saturn's moon Titan and the shape of the rings of Saturn.[253] In 1677, Edmond Halley observed a transit of Mercury across the Sun, leading him to realize that observations of the solar parallax of a planet (more ideally using the transit of Venus) could be used to trigonometrically determine the distances between Earth, Venus, and the Sun.[254] Halley's friend Isaac Newton, in his magisterial Principia Mathematica of 1687, demonstrated that celestial bodies are not quintessentially different from Earthly ones: the same laws of motion and of gravity apply on Earth and in the skies.[55]: 142 

True-scale Solar System poster made by Emanuel Bowen in 1747. At that time, Uranus, Neptune, nor the asteroid belts have been discovered yet.

The term "Solar System" entered the English language by 1704, when John Locke used it to refer to the Sun, planets, and comets.[255] In 1705, Halley realized that repeated sightings of a comet were of the same object, returning regularly once every 75–76 years. This was the first evidence that anything other than the planets repeatedly orbited the Sun,[256] though Seneca had theorized this about comets in the 1st century.[257] Careful observations of the 1769 transit of Venus allowed astronomers to calculate the average Earth–Sun distance as 93,726,900 miles (150,838,800 km), only 0.8% greater than the modern value.[258]

Uranus, having occasionally been observed since antiquity, was recognized to be a planet orbiting beyond Saturn by 1783.[259] In 1838, Friedrich Bessel successfully measured a stellar parallax, an apparent shift in the position of a star created by Earth's motion around the Sun, providing the first direct, experimental proof of heliocentrism.[260] Neptune was identified as a planet some years later, in 1846, thanks to its gravitational pull causing a slight but detectable variation in the orbit of Uranus.[261] Mercury's orbital anomaly observations also led to searches for Vulcan, a planet interior of Mercury, but these attempts were quashed with Albert Einstein's theory of general relativity in 1915.[262]

In the 20th century, humans began their space exploration around the Solar System, starting with placing telescopes in space since the 1960s.[263] By 1989, all eight planets have been visited by space probes.[264] In addition, probes have also returned samples from comets[265] and asteroids,[266] as well as flown through the Sun's corona[267] and visited two dwarf planets (Pluto and Ceres).[268][269] Humans have landed on the Moon during the Apollo program in the 1960s and 1970s[270] and will return to the Moon in the 2020s with the Artemis program.[271] Discoveries in the 20th and 21st century has prompted the redefinition of the term planet in 2006, hence the demotion of Pluto to a dwarf planet,[272] and further interest in trans-Neptunian objects.[273]

See also


  1. ^ a b The date is based on the oldest inclusions found to date in meteorites, 4568.2+0.2
    million years, and is thought to be the date of the formation of the first solid material in the collapsing nebula.[15]
  2. ^ Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar System" and "solar system" structures in their naming guidelines document Archived 25 July 2021 at the Wayback Machine. The name is commonly rendered in lower case ('solar system'), as, for example, in the Oxford English Dictionary and Merriam-Webster's 11th Collegiate Dictionary Archived 27 January 2008 at the Wayback Machine.
  3. ^ The International Astronomical Union's Minor Planet Center has yet to officially list Quaoar, Sedna and Gonggong as dwarf planets as of 2024
  4. ^ For more classifications of Solar System objects, see List of minor-planet groups and Comet § Classification.
  5. ^ "Low-mass" is a relative term; the Sun is still more massive than 95% of stars in the galaxy.[35]
  6. ^ a b The mass of the Solar System excluding the Sun, Jupiter and Saturn can be determined by adding together all the calculated masses for its largest objects and using rough calculations for the masses of the Oort cloud (estimated at roughly 3 Earth masses),[37] the Kuiper belt (estimated at 0.1 Earth mass)[38] and the asteroid belt (estimated to be 0.0005 Earth mass)[39] for a total, rounded upwards, of ~37 Earth masses, or 8.1% of the mass in orbit around the Sun. With the combined masses of Uranus and Neptune (~31 Earth masses) subtracted, the remaining ~6 Earth masses of material comprise 1.3% of the total orbiting mass.
  7. ^ If is the angle between the north pole of the ecliptic and the north galactic pole then:

    where = 27° 07′ 42.01″ and = 12h 51m 26.282s are the declination and right ascension of the north galactic pole,[240] whereas = 66° 33′ 38.6″ and = 18h 0m 00s are those for the north pole of the ecliptic. (Both pairs of coordinates are for J2000 epoch.) The result of the calculation is 60.19°.


  1. ^ "Our Local Galactic Neighborhood". Interstellar Probe Project. NASA. 2000. Archived from the original on 21 November 2013. Retrieved 8 August 2012.
  2. ^ Hurt, R. (8 November 2017). "The Milky Way Galaxy". Retrieved 19 April 2024.
  3. ^ Lurie, John C.; Henry, Todd J.; Jao, Wei-Chun; Quinn, Samuel N.; Winters, Jennifer G.; Ianna, Philip A.; Koerner, David W.; Riedel, Adric R.; Subasavage, John P. (2014). "The Solar neighborhood. XXXIV. A search for planets orbiting nearby M dwarfs using astrometry". The Astronomical Journal. 148 (5): 91. arXiv:1407.4820. Bibcode:2014AJ....148...91L. doi:10.1088/0004-6256/148/5/91. S2CID 118492541.
  4. ^ "The One Hundred Nearest Star Systems". Research Consortium On Nearby Stars. Georgia State University. 7 September 2007. Archived from the original on 12 November 2007. Retrieved 2 December 2014.
  5. ^ "Solar System Objects". NASA/JPL Solar System Dynamics. Archived from the original on 7 July 2021. Retrieved 14 August 2023.
  6. ^ a b "Latest Published Data". The International Astronomical Union Minor Planet Center. Retrieved 10 April 2024.{{cite web}}: CS1 maint: url-status (link)
  7. ^ Yeomans, Donald K. "HORIZONS Web-Interface for Neptune Barycenter (Major Body=8)". JPL Horizons On-Line Ephemeris System. Archived from the original on 7 September 2021. Retrieved 18 July 2014.—Select "Ephemeris Type: Orbital Elements", "Time Span: 2000-01-01 12:00 to 2000-01-02". ("Target Body: Neptune Barycenter" and "Center: Solar System Barycenter (@0)".)
  8. ^ Chiang; Jordan, A. B.; Millis, R. L.; Buie, M. W.; Wasserman, L. H.; Elliot, J. L.; et al. (2003). "Resonance Occupation in the Kuiper Belt: Case Examples of the 5:2 and Trojan Resonances". The Astronomical Journal. 126 (1): 430–443. arXiv:astro-ph/0301458. Bibcode:2003AJ....126..430C. doi:10.1086/375207. S2CID 54079935.
  9. ^ C. de la Fuente Marcos & R. de la Fuente Marcos (January 2024). "Past the outer rim, into the unknown: structures beyond the Kuiper Cliff". Monthly Notices of the Royal Astronomical Society Letters. 527 (1) (published 20 September 2023): L110–L114. arXiv:2309.03885. Bibcode:2024MNRAS.527L.110D. doi:10.1093/mnrasl/slad132. Archived from the original on 28 October 2023. Retrieved 28 September 2023.
  10. ^ a b Mumma, M. J.; Disanti, M. A.; Dello Russo, N.; Magee-Sauer, K.; Gibb, E.; Novak, R. (2003). "Remote infrared observations of parent volatiles in comets: A window on the early solar system". Advances in Space Research. 31 (12): 2563–2575. Bibcode:2003AdSpR..31.2563M. CiteSeerX doi:10.1016/S0273-1177(03)00578-7.
  11. ^ Greicius, Tony (5 May 2015). "NASA Spacecraft Embarks on Historic Journey Into Interstellar Space".
  12. ^ Francis, Charles; Anderson, Erik (June 2014). "Two estimates of the distance to the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 441 (2): 1105–1114. arXiv:1309.2629. Bibcode:2014MNRAS.441.1105F. doi:10.1093/mnras/stu631. S2CID 119235554.
  13. ^ a b "Sun: Facts - NASA Science". Retrieved 19 April 2024.
  14. ^ "IAU Office of Astronomy for Education". IAU Office of Astronomy for Education. Retrieved 11 December 2023.
  15. ^ Bouvier, A.; Wadhwa, M. (2010). "The age of the Solar System redefined by the oldest Pb–Pb age of a meteoritic inclusion". Nature Geoscience. 3 (9): 637–641. Bibcode:2010NatGe...3..637B. doi:10.1038/NGEO941. S2CID 56092512.
  16. ^ a b c Zabludoff, Ann. "Lecture 13: The Nebular Theory of the origin of the Solar System". NATS 102: The Physical Universe. University of Arizona. Archived from the original on 22 August 2011. Retrieved 27 December 2006.
  17. ^ a b Irvine, W. M. (1983). "The chemical composition of the pre-solar nebula". Cometary exploration; Proceedings of the International Conference. Vol. 1. p. 3. Bibcode:1983coex....1....3I.
  18. ^ Greaves, Jane S. (7 January 2005). "Disks Around Stars and the Growth of Planetary Systems". Science. 307 (5706): 68–71. Bibcode:2005Sci...307...68G. doi:10.1126/science.1101979. PMID 15637266. S2CID 27720602.
  19. ^ National Research Council, Division on Engineering and Physical Sciences; Space Studies Board, Committee on Planetary and Lunar Exploration (1990). "3. Present Understanding of the Origin of Planetary Systems". Strategy for the Detection and Study of Other Planetary Systems and Extrasolar Planetary Materials: 1990–2000. Washington D.C.: National Academies Press. pp. 21–33. ISBN 978-0309041935. Archived from the original on 9 April 2022. Retrieved 9 April 2022.
  20. ^ Boss, A. P.; Durisen, R. H. (2005). "Chondrule-forming Shock Fronts in the Solar Nebula: A Possible Unified Scenario for Planet and Chondrite Formation". The Astrophysical Journal. 621 (2): L137. arXiv:astro-ph/0501592. Bibcode:2005ApJ...621L.137B. doi:10.1086/429160. S2CID 15244154.
  21. ^ a b c d e Bennett, Jeffrey O. (2020). "Chapter 8.2". The cosmic perspective (9th ed.). Hoboken, NJ: Pearson. ISBN 978-0-134-87436-4.
  22. ^ Nagasawa, M.; Thommes, E. W.; Kenyon, S. J.; Bromley, B. C.; Lin, D. N. C. (2007). "The Diverse Origins of Terrestrial-Planet Systems" (PDF). In Reipurth, B.; Jewitt, D.; Keil, K. (eds.). Protostars and Planets V. Tucson: University of Arizona Press. pp. 639–654. Bibcode:2007prpl.conf..639N. Archived (PDF) from the original on 12 April 2022. Retrieved 10 April 2022.
  23. ^ Yi, Sukyoung; Demarque, Pierre; Kim, Yong-Cheol; Lee, Young-Wook; Ree, Chang H.; Lejeune, Thibault; Barnes, Sydney (2001). "Toward Better Age Estimates for Stellar Populations: The Y2 Isochrones for Solar Mixture". Astrophysical Journal Supplement. 136 (2): 417–437. arXiv:astro-ph/0104292. Bibcode:2001ApJS..136..417Y. doi:10.1086/321795. S2CID 118940644.
  24. ^ a b Gough, D. O. (November 1981). "Solar Interior Structure and Luminosity Variations". Solar Physics. 74 (1): 21–34. Bibcode:1981SoPh...74...21G. doi:10.1007/BF00151270. S2CID 120541081.
  25. ^ Shaviv, Nir J. (2003). "Towards a Solution to the Early Faint Sun Paradox: A Lower Cosmic Ray Flux from a Stronger Solar Wind". Journal of Geophysical Research. 108 (A12): 1437. arXiv:astroph/0306477. Bibcode:2003JGRA..108.1437S. doi:10.1029/2003JA009997. S2CID 11148141.
  26. ^ Chrysostomou, A.; Lucas, P. W. (2005). "The Formation of Stars". Contemporary Physics. 46 (1): 29–40. Bibcode:2005ConPh..46...29C. doi:10.1080/0010751042000275277. S2CID 120275197.
  27. ^ a b c Schröder, K.-P.; Connon Smith, Robert (May 2008). "Distant future of the Sun and Earth revisited". Monthly Notices of the Royal Astronomical Society. 386 (1): 155–163. arXiv:0801.4031. Bibcode:2008MNRAS.386..155S. doi:10.1111/j.1365-2966.2008.13022.x. S2CID 10073988.
  28. ^ Malhotra, R.; Holman, Matthew; Ito, Takashi (October 2001). "Chaos and stability of the solar system". Proceedings of the National Academy of Sciences. 98 (22): 12342–12343. Bibcode:2001PNAS...9812342M. doi:10.1073/pnas.231384098. PMC 60054. PMID 11606772.
  29. ^ Sean Raymond; et al. (27 November 2023). "Future trajectories of the Solar System: dynamical simulations of stellar encounters within 100 au". Monthly Notices of the Royal Astronomical Society. 527 (3): 6126–6138. arXiv:2311.12171. Bibcode:2024MNRAS.527.6126R. doi:10.1093/mnras/stad3604.
  30. ^ Aungwerojwit, Amornrat; Gänsicke, Boris T; Dhillon, Vikram S; Drake, Andrew; Inight, Keith; Kaye, Thomas G; Marsh, T R; Mullen, Ed; Pelisoli, Ingrid; Swan, Andrew (2024). "Long-term variability in debris transiting white dwarfs". Monthly Notices of the Royal Astronomical Society. 530 (1): 117–128. arXiv:2404.04422. doi:10.1093/mnras/stae750.
  31. ^ "Planetary Nebulas". Harvard & Smithsonian Center for Astrophysics. Retrieved 6 April 2024.
  32. ^ Gesicki, K.; Zijlstra, A. A.; Miller Bertolami, M. M. (7 May 2018). "The mysterious age invariance of the planetary nebula luminosity function bright cut-off". Nature Astronomy. 2 (7): 580–584. arXiv:1805.02643. Bibcode:2018NatAs...2..580G. doi:10.1038/s41550-018-0453-9. S2CID 256708667.
  33. ^ "The Planets". NASA. Retrieved 6 April 2024.
  34. ^ "Kuiper Belt: Facts". NASA. Retrieved 6 April 2024.
  35. ^ Robles, José A.; Lineweaver, Charles H.; Grether, Daniel; Flynn, Chris; Egan, Chas A.; Pracy, Michael B.; Holmberg, Johan; Gardner, Esko (2008). "A Comprehensive Comparison of the Sun to Other Stars: Searching for Self-Selection Effects". The Astrophysical Journal. 684 (691): 691–706. arXiv:0805.2962. Bibcode:2008ApJ...684..691R. doi:10.1086/589985.
  36. ^ Woolfson, M. (2000). "The origin and evolution of the solar system". Astronomy & Geophysics. 41 (1): 1.12–1.19. Bibcode:2000A&G....41a..12W. doi:10.1046/j.1468-4004.2000.00012.x.
  37. ^ Morbidelli, Alessandro (2005). "Origin and dynamical evolution of comets and their reservoirs". arXiv:astro-ph/0512256.
  38. ^ a b c Delsanti, Audrey; Jewitt, David (2006). "The Solar System Beyond The Planets" (PDF). Institute for Astronomy, University of Hawaii. Archived from the original (PDF) on 29 January 2007. Retrieved 3 January 2007.
  39. ^ a b Krasinsky, G. A.; Pitjeva, E. V.; Vasilyev, M. V.; Yagudina, E. I. (July 2002). "Hidden Mass in the Asteroid Belt". Icarus. 158 (1): 98–105. Bibcode:2002Icar..158...98K. doi:10.1006/icar.2002.6837.
  40. ^ "The Sun's Vital Statistics". Stanford Solar Center. Archived from the original on 14 October 2012. Retrieved 29 July 2008, citing Eddy, J. (1979). A New Sun: The Solar Results From Skylab. NASA. p. 37. NASA SP-402. Archived from the original on 30 July 2021. Retrieved 12 July 2017.
  41. ^ Williams, David R. (7 September 2006). "Saturn Fact Sheet". NASA. Archived from the original on 4 August 2011. Retrieved 31 July 2007.
  42. ^ a b Williams, David R. (23 December 2021). "Jupiter Fact Sheet". NASA Goddard Space Flight Center. Archived from the original on 22 January 2018. Retrieved 28 March 2022.
  43. ^ Weissman, Paul Robert; Johnson, Torrence V. (2007). Encyclopedia of the solar system. Academic Press. p. 615. ISBN 978-0-12-088589-3.
  44. ^ a b c Podolak, M.; Weizman, A.; Marley, M. (December 1995). "Comparative models of Uranus and Neptune". Planetary and Space Science. 43 (12): 1517–1522. Bibcode:1995P&SS...43.1517P. doi:10.1016/0032-0633(95)00061-5.
  45. ^ a b c d Podolak, M.; Podolak, J. I.; Marley, M. S. (February 2000). "Further investigations of random models of Uranus and Neptune". Planetary and Space Science. 48 (2–3): 143–151. Bibcode:2000P&SS...48..143P. doi:10.1016/S0032-0633(99)00088-4. Archived from the original on 21 December 2019. Retrieved 25 August 2019.
  46. ^ Zellik, Michael (2002). Astronomy: The Evolving Universe (9th ed.). Cambridge University Press. p. 240. ISBN 978-0-521-80090-7. OCLC 223304585.
  47. ^ Placxo, Kevin W.; Gross, Michael (2006). Astrobiology: a brief introduction. JHU Press. p. 66. ISBN 978-0-8018-8367-5. Archived from the original on 6 August 2021. Retrieved 12 November 2020.
  48. ^ a b Levison, H.F.; Morbidelli, A. (27 November 2003). "The formation of the Kuiper belt by the outward transport of bodies during Neptune's migration". Nature. 426 (6965): 419–421. Bibcode:2003Natur.426..419L. doi:10.1038/nature02120. PMID 14647375. S2CID 4395099.
  49. ^ Levison, Harold F.; Duncan, Martin J. (1997). "From the Kuiper Belt to Jupiter-Family Comets: The Spatial Distribution of Ecliptic Comets". Icarus. 127 (1): 13–32. Bibcode:1997Icar..127...13L. doi:10.1006/icar.1996.5637.
  50. ^ Bennett, Jeffrey O.; Donahue, Megan; Schneider, Nicholas; Voit, Mark (2020). "4.5 Orbits, Tides, and the Acceleration of Gravity". The Cosmic Perspective (9th ed.). Hoboken, NJ: Pearson. ISBN 978-0-134-87436-4. OCLC 1061866912.
  51. ^ Grossman, Lisa (13 August 2009). "Planet found orbiting its star backwards for first time". New Scientist. Archived from the original on 17 October 2012. Retrieved 10 October 2009.
  52. ^ Nakano, Syuichi (2001). "OAA computing section circular". Oriental Astronomical Association. Archived from the original on 21 September 2019. Retrieved 15 May 2007.
  53. ^ Agnor, Craig B.; Hamilton, Douglas P. (May 2006). "Neptune's capture of its moon Triton in a binary–planet gravitational encounter". Nature. 441 (7090): 192–194. Bibcode:2006Natur.441..192A. doi:10.1038/nature04792. ISSN 1476-4687. PMID 16688170. S2CID 4420518. Archived from the original on 15 April 2022. Retrieved 28 March 2022.
  54. ^ Gallant, Roy A. (1980). Sedeen, Margaret (ed.). National Geographic Picture Atlas of Our Universe. Washington, D.C.: National Geographic Society. p. 82. ISBN 0-87044-356-9. OCLC 6533014. Archived from the original on 20 April 2022. Retrieved 28 March 2022.
  55. ^ a b Frautschi, Steven C.; Olenick, Richard P.; Apostol, Tom M.; Goodstein, David L. (2007). The Mechanical Universe: Mechanics and Heat (Advanced ed.). Cambridge [Cambridgeshire]: Cambridge University Press. ISBN 978-0-521-71590-4. OCLC 227002144.
  56. ^ a b Feynman, Richard P.; Leighton, Robert B.; Sands, Matthew L. (1989) [1965]. The Feynman Lectures on Physics, Volume 1. Reading, Mass.: Addison-Wesley Pub. Co. ISBN 0-201-02010-6. OCLC 531535.
  57. ^ Lecar, Myron; Franklin, Fred A.; Holman, Matthew J.; Murray, Norman J. (2001). "Chaos in the Solar System". Annual Review of Astronomy and Astrophysics. 39: 581–631. arXiv:astro-ph/0111600. Bibcode:2001ARA&A..39..581L. doi:10.1146/annurev.astro.39.1.581. S2CID 55949289.
  58. ^ Piccirillo, Lucio (2020). Introduction to the Maths and Physics of the Solar System. CRC Press. p. 210. ISBN 978-0429682803. Archived from the original on 30 July 2022. Retrieved 10 May 2022.
  59. ^ a b Marochnik, L.; Mukhin, L. (1995). "Is Solar System Evolution Cometary Dominated?". In Shostak, G.S. (ed.). Progress in the Search for Extraterrestrial Life. Astronomical Society of the Pacific Conference Series. Vol. 74. p. 83. Bibcode:1995ASPC...74...83M. ISBN 0-937707-93-7.
  60. ^ Bi, S. L.; Li, T. D.; Li, L. H.; Yang, W. M. (2011). "Solar Models with Revised Abundance". The Astrophysical Journal. 731 (2): L42. arXiv:1104.1032. Bibcode:2011ApJ...731L..42B. doi:10.1088/2041-8205/731/2/L42. S2CID 118681206.
  61. ^ Standish, E. M. (April 2005). "The Astronomical Unit now". Proceedings of the International Astronomical Union. 2004: 163–179. Bibcode:2005tvnv.conf..163S. doi:10.1017/S1743921305001365. S2CID 55944238.
  62. ^ Emilio, Marcelo; Kuhn, Jeff R.; Bush, Rock I.; Scholl, Isabelle F. (2012). "Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits". The Astrophysical Journal. 750 (2): 135. arXiv:1203.4898. Bibcode:2012ApJ...750..135E. doi:10.1088/0004-637X/750/2/135. S2CID 119255559.
  63. ^ Williams, David R. (23 December 2021). "Neptune Fact Sheet". NASA Goddard Space Flight Center. Archived from the original on 19 November 2016. Retrieved 28 March 2022.
  64. ^ Jaki, Stanley L. (1 July 1972). "The Early History of the Titius-Bode Law". American Journal of Physics. 40 (7): 1014–1023. Bibcode:1972AmJPh..40.1014J. doi:10.1119/1.1986734. ISSN 0002-9505. Archived from the original on 20 April 2022. Retrieved 2 April 2022.
  65. ^ Phillips, J. P. (1965). "Kepler's Echinus". Isis. 56 (2): 196–200. doi:10.1086/349957. ISSN 0021-1753. JSTOR 227915. S2CID 145268784.
  66. ^ Boss, Alan (October 2006). "Is it a coincidence that most of the planets fall within the Titius-Bode law's boundaries?". Astronomy. Ask Astro. Vol. 30, no. 10. p. 70. Archived from the original on 16 March 2022. Retrieved 9 April 2022.
  67. ^ Ottewell, Guy (1989). "The Thousand-Yard Model: or, Earth as a Peppercorn". NOAO Educational Outreach Office. Archived from the original on 10 July 2016. Retrieved 10 May 2012.
  68. ^ "Tours of Model Solar Systems". University of Illinois. Archived from the original on 12 April 2011. Retrieved 10 May 2012.
  69. ^ "Luleå är Sedna. I alla fall om vår sol motsvaras av Globen i Stockholm". Norrbotten Kuriren (in Swedish). Archived from the original on 15 July 2010. Retrieved 10 May 2010.
  70. ^ See, for example, Office of Space Science (9 July 2004). "Solar System Scale". NASA Educator Features. Archived from the original on 27 August 2016. Retrieved 2 April 2013.
  71. ^ Kallenrode, May-Britt (2004). Space Physics: An introduction to plasmas and particles in the heliosphere and magnetospheres (3rd ed.). Berlin: Springer. p. 150. ISBN 978-3-540-20617-0. OCLC 53443301. Archived from the original on 20 April 2022. Retrieved 1 April 2022.
  72. ^ a b c Steigerwald, Bill (24 May 2005). "Voyager Enters Solar System's Final Frontier". NASA. Archived from the original on 16 May 2020. Retrieved 2 April 2007.
  73. ^ Jorgensen, J. L.; Benn, M.; Connerney, J. E. P.; Denver, T.; Jorgensen, P. S.; Andersen, A. C.; Bolton, S. J. (March 2021). "Distribution of Interplanetary Dust Detected by the Juno Spacecraft and Its Contribution to the Zodiacal Light". Journal of Geophysical Research: Planets. 126 (3). Bibcode:2021JGRE..12606509J. doi:10.1029/2020JE006509. ISSN 2169-9097. S2CID 228840132.
  74. ^ "ESA scientist discovers a way to shortlist stars that might have planets". ESA Science and Technology. 2003. Archived from the original on 2 May 2013. Retrieved 3 February 2007.
  75. ^ Landgraf, M.; Liou, J.-C.; Zook, H. A.; Grün, E. (May 2002). "Origins of Solar System Dust beyond Jupiter" (PDF). The Astronomical Journal. 123 (5): 2857–2861. arXiv:astro-ph/0201291. Bibcode:2002AJ....123.2857L. doi:10.1086/339704. S2CID 38710056. Archived (PDF) from the original on 15 May 2016. Retrieved 9 February 2007.
  76. ^ Phillips, Tony (15 February 2001). "The Sun Does a Flip". NASA Science: Share the Science. Archived from the original on 1 April 2022. Retrieved 1 April 2022.
  77. ^ Fraknoi, Andrew; Morrison, David; Wolff, Sidney C.; et al. (2022) [2016]. "15.4 Space weather". Astronomy. Houston, Texas: OpenStax. ISBN 978-1-947-17224-1. OCLC 961476196. Archived from the original on 19 July 2020. Retrieved 9 March 2022.
  78. ^ "A Star with two North Poles". NASA Science: Share the Science. 22 April 2003. Archived from the original on 1 April 2022. Retrieved 1 April 2022.
  79. ^ Riley, Pete (2002). "Modeling the heliospheric current sheet: Solar cycle variations". Journal of Geophysical Research. 107 (A7): 1136. Bibcode:2002JGRA..107.1136R. doi:10.1029/2001JA000299.
  80. ^ Langner, U. W.; Potgieter, M. S. (2005). "Effects of the position of the solar wind termination shock and the heliopause on the heliospheric modulation of cosmic rays". Advances in Space Research. 35 (12): 2084–2090. Bibcode:2005AdSpR..35.2084L. doi:10.1016/j.asr.2004.12.005.
  81. ^ Dyches, Preston; Chou, Felcia (7 April 2015). "The Solar System and Beyond is Awash in Water". NASA. Archived from the original on 10 April 2015. Retrieved 8 April 2015.
  82. ^ Robert T. Pappalardo; William B. McKinnon; K. Khurana (2009). Europa. University of Arizona Press. p. 658. ISBN 978-0-8165-2844-8. Extract of page 658
  83. ^ a b c d e Martin, Rebecca G.; Livio, Mario (2015). "The Solar System as an Exoplanetary System". The Astrophysical Journal. 810 (2): 105. arXiv:1508.00931. Bibcode:2015ApJ...810..105M. doi:10.1088/0004-637X/810/2/105. S2CID 119119390.
  84. ^ Kohler, Susanna (25 September 2015). "How Normal is Our Solar System?". Aas Nova Highlights. American Astronomical Society: 313. Bibcode:2015nova.pres..313K. Archived from the original on 7 April 2022. Retrieved 31 March 2022.
  85. ^ Sheppard, Scott S.; Trujillo, Chadwick (7 December 2016). "New extreme trans-Neptunian objects: Toward a super-Earth in the outer solar system". The Astronomical Journal. 152 (6): 221. arXiv:1608.08772. Bibcode:2016AJ....152..221S. doi:10.3847/1538-3881/152/6/221. ISSN 1538-3881. S2CID 119187392.
  86. ^ Volk, Kathryn; Gladman, Brett (2015). "Consolidating and Crushing Exoplanets: Did it happen here?". The Astrophysical Journal Letters. 806 (2): L26. arXiv:1502.06558. Bibcode:2015ApJ...806L..26V. doi:10.1088/2041-8205/806/2/L26. S2CID 118052299.
  87. ^ Goldreich, Peter; Lithwick, Yoram; Sari, Re'em (2004). "Final Stages of Planet Formation". The Astrophysical Journal. 614 (1): 497–507. arXiv:astro-ph/0404240. Bibcode:2004ApJ...614..497G. doi:10.1086/423612. S2CID 16419857.
  88. ^ "Sun: Facts & Figures". NASA. Archived from the original on 2 January 2008. Retrieved 14 May 2009.
  89. ^ Woolfson, M. (2000). "The origin and evolution of the solar system". Astronomy & Geophysics. 41 (1): 12. Bibcode:2000A&G....41a..12W. doi:10.1046/j.1468-4004.2000.00012.x.
  90. ^ Zirker, Jack B. (2002). Journey from the Center of the Sun. Princeton University Press. pp. 120–127. ISBN 978-0-691-05781-1.
  91. ^ "What Color is the Sun?". NASA. Retrieved 6 April 2024.
  92. ^ "What Color is the Sun?". Stanford Solar Center. Archived from the original on 30 October 2017. Retrieved 23 May 2016.
  93. ^ Mejías, Andrea; Minniti, Dante; Alonso-García, Javier; Beamín, Juan Carlos; Saito, Roberto K.; Solano, Enrique (2022). "VVVX near-IR photometry for 99 low-mass stars in the Gaia EDR3 Catalog of Nearby Stars". Astronomy & Astrophysics. 660: A131. arXiv:2203.00786. Bibcode:2022A&A...660A.131M. doi:10.1051/0004-6361/202141759. S2CID 246842719.
  94. ^ van Albada, T.S.; Baker, Norman (1973). "On the Two Oosterhoff Groups of Globular Clusters". The Astrophysical Journal. 185: 477–498. Bibcode:1973ApJ...185..477V. doi:10.1086/152434.
  95. ^ Lineweaver, Charles H. (9 March 2001). "An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect". Icarus. 151 (2): 307–313. arXiv:astro-ph/0012399. Bibcode:2001Icar..151..307L. CiteSeerX doi:10.1006/icar.2001.6607. S2CID 14077895.
  96. ^ "Inner Solar System". NASA Science: Share the Science. Archived from the original on 10 April 2022. Retrieved 2 April 2022.
  97. ^ Del Genio, Anthony D.; Brain, David; Noack, Lena; Schaefer, Laura (2020). "The Inner Solar System's Habitability Through Time". In Meadows, Victoria S.; Arney, Giada N.; Schmidt, Britney; Des Marais, David J. (eds.). Planetary Astrobiology. University of Arizona Press. p. 420. arXiv:1807.04776. Bibcode:2018arXiv180704776D. ISBN 978-0816540655.
  98. ^ Durda, D .D.; Stern, S. A.; Colwell, W. B.; Parker, J. W.; Levison, H. F.; Hassler, D. M. (2004). "A New Observational Search for Vulcanoids in SOHO/LASCO Coronagraph Images". Icarus. 148 (1): 312–315. Bibcode:2000Icar..148..312D. doi:10.1006/icar.2000.6520.
  99. ^ Steffl, A. J.; Cunningham, N. J.; Shinn, A. B.; Stern, S. A. (2013). "A Search for Vulcanoids with the STEREO Heliospheric Imager". Icarus. 233 (1): 48–56. arXiv:1301.3804. Bibcode:2013Icar..223...48S. doi:10.1016/j.icarus.2012.11.031. S2CID 118612132.
  100. ^ Bolin, Bryce T.; Ahumada, T.; van Dokkum, P.; Fremling, C.; Granvik, M.; Hardegree-Ullmann, K. K.; Harikane, Y.; Purdum, J. N.; Serabyn, E.; Southworth, J.; Zhai, C. (November 2022). "The discovery and characterization of (594913) 'Ayló'chaxnim, a kilometre sized asteroid inside the orbit of Venus". Monthly Notices of the Royal Astronomical Society: Letters. 517 (1): L49–L54. arXiv:2208.07253. Bibcode:2022MNRAS.517L..49B. doi:10.1093/mnrasl/slac089. Retrieved 1 October 2022.
  101. ^ Baalke, Ron. "Near-Earth Object Groups". Jet Propulsion Laboratory. NASA. Archived from the original on 2 February 2002. Retrieved 11 November 2016.
  102. ^ a b Ryden, Robert (December 1999). "Astronomical Math". The Mathematics Teacher. 92 (9): 786–792. doi:10.5951/MT.92.9.0786. ISSN 0025-5769. JSTOR 27971203. Archived from the original on 12 April 2022. Retrieved 29 March 2022.
  103. ^ a b c d e f g h Williams, David (27 December 2021). "Planetary Fact Sheet - Metric". NASA Goddard Space Flight Center. Retrieved 11 December 2022.
  104. ^ Watters, Thomas R.; Solomon, Sean C.; Robinson, Mark S.; Head, James W.; André, Sarah L.; Hauck, Steven A.; Murchie, Scott L. (August 2009). "The tectonics of Mercury: The view after MESSENGER's first flyby". Earth and Planetary Science Letters. 285 (3–4): 283–296. Bibcode:2009E&PSL.285..283W. doi:10.1016/j.epsl.2009.01.025.
  105. ^ Domingue, Deborah L.; Koehn, Patrick L.; et al. (2009). "Mercury's Atmosphere: A Surface-Bounded Exosphere". Space Science Reviews. 131 (1–4): 161–186. Bibcode:2007SSRv..131..161D. doi:10.1007/s11214-007-9260-9. S2CID 121301247. The composition of Mercury's exosphere, with its abundant H and He, clearly indicates a strong solar wind source. Once solar wind plasma and particles gain access to the magnetosphere, they predominantly precipitate to the surface, where solar wind species are neutralized, thermalized, and released again into the exosphere. Moreover, bombardment of the surface by solar wind particles, especially energetic ions, contributes to ejection of neutral species from the surface into the exosphere (via "sputtering") as well as other chemical and physical surface modification processes.
  106. ^ Bullock, Mark Alan (1997). The Stability of Climate on Venus (PDF) (PhD thesis). Southwest Research Institute. Archived from the original (PDF) on 14 June 2007. Retrieved 26 December 2006.
  107. ^ Rincon, Paul (1999). "Climate Change as a Regulator of Tectonics on Venus" (PDF). Johnson Space Center Houston, TX, Institute of Meteoritics, University of New Mexico, Albuquerque, NM. Archived from the original (PDF) on 14 June 2007. Retrieved 19 November 2006.
  108. ^ Elkins-Tanton, L. T.; Smrekar, S. E.; Hess, P. C.; Parmentier, E. M. (March 2007). "Volcanism and volatile recycling on a one-plate planet: Applications to Venus". Journal of Geophysical Research. 112 (E4). Bibcode:2007JGRE..112.4S06E. doi:10.1029/2006JE002793. E04S06.
  109. ^ "What are the characteristics of the Solar System that lead to the origins of life?". NASA Science (Big Questions). Archived from the original on 8 April 2010. Retrieved 30 August 2011.
  110. ^ Hall, Shannon (20 July 2017). "Earth's Tectonic Activity May Be Crucial for Life—and Rare in Our Galaxy". Scientific American. Archived from the original on 12 May 2022. Retrieved 12 May 2022.
  111. ^ Haynes, H. M., ed. (2016–2017). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. p. 14-3. ISBN 978-1-4987-5428-6.
  112. ^ Zimmer, Carl (3 October 2013). "Earth's Oxygen: A Mystery Easy to Take for Granted". The New York Times. Archived from the original on 3 October 2013. Retrieved 3 October 2013.
  113. ^ Pentreath, R. J. (2021). Radioecology: Sources and Consequences of Ionising Radiation in the Environment. Cambridge University Press. pp. 94–97. ISBN 978-1009040334. Archived from the original on 20 April 2022. Retrieved 12 April 2022.
  114. ^ "Facts About Earth - NASA Science". NASA Science. Retrieved 11 January 2024.
  115. ^ Gatling, David C.; Leovy, Conway (2007). "Mars Atmosphere: History and Surface Interactions". In Lucy-Ann McFadden; et al. (eds.). Encyclopaedia of the Solar System. pp. 301–314.
  116. ^ Noever, David (2004). "Modern Martian Marvels: Volcanoes?". NASA Astrobiology Magazine. Archived from the original on 14 March 2020. Retrieved 23 July 2006.{{cite web}}: CS1 maint: unfit URL (link)
  117. ^ Peplow, Mark (6 May 2004). "How Mars got its rust". Nature: news040503–6. doi:10.1038/news040503-6. ISSN 0028-0836. Archived from the original on 7 April 2022. Retrieved 9 April 2022.
  118. ^ "Polar Caps". Mars Education at Arizona State University. Retrieved 6 January 2022.
  119. ^ Sheppard, Scott S.; Jewitt, David; Kleyna, Jan (2004). "A Survey for Outer Satellites of Mars: Limits to Completeness" (PDF). Astronomical Journal. Archived (PDF) from the original on 3 March 2016. Retrieved 26 December 2006.
  120. ^ Rosenblatt, Pascal; Charnoz, Sébastien; Dunseath, Kevin M.; Terao-Dunseath, Mariko; Trinh, Antony; Hyodo, Ryuki; Genda, Hidenori; Toupin, Stéven (2016). "Accretion of Phobos and Deimos in an extended debris disc stirred by transient moons" (PDF). Nature Geoscience. 9 (8): 581. Bibcode:2016NatGe...9..581R. doi:10.1038/ngeo2742. S2CID 133174714. Archived (PDF) from the original on 9 March 2020. Retrieved 25 August 2019.
  121. ^ "IAU Planet Definition Committee". International Astronomical Union. 2006. Archived from the original on 3 June 2009. Retrieved 1 March 2009.
  122. ^ "Are Kuiper Belt Objects asteroids? Are large Kuiper Belt Objects planets?". Cornell University. Archived from the original on 3 January 2009. Retrieved 1 March 2009.
  123. ^ Rubin, Alan E.; Grossman, Jeffrey N. (February 2010). "Meteorite and meteoroid: new comprehensive definitions". Meteoritics and Planetary Science. 45 (1): 114. Bibcode:2010M&PS...45..114R. doi:10.1111/j.1945-5100.2009.01009.x. S2CID 129972426. Archived from the original on 25 March 2022. Retrieved 10 April 2022.
  124. ^ Perlerin, Vincent (26 September 2017). "Definitions of terms in meteor astronomy (IAU)". International Meteor Organization. Archived from the original on 23 January 2018. Retrieved 10 April 2022.
  125. ^ Petit, J.-M.; Morbidelli, A.; Chambers, J. (2001). "The Primordial Excitation and Clearing of the Asteroid Belt" (PDF). Icarus. 153 (2): 338–347. Bibcode:2001Icar..153..338P. doi:10.1006/icar.2001.6702. Archived from the original (PDF) on 21 February 2007. Retrieved 22 March 2007.
  126. ^ Tedesco, Edward F.; Cellino, Alberto; Zappalá, Vincenzo (June 2005). "The Statistical Asteroid Model. I. The Main-Belt Population for Diameters Greater than 1 Kilometer". The Astronomical Journal. 129 (6): 2869–2886. Bibcode:2005AJ....129.2869T. doi:10.1086/429734. ISSN 0004-6256. S2CID 119906696.
  127. ^ "Cassini Passes Through Asteroid Belt". NASA. 14 April 2000. Archived from the original on 25 January 2021. Retrieved 1 March 2021.
  128. ^ "Exploration: Ceres". NASA Science: Solar System Exploration. 26 June 2019. Archived from the original on 30 October 2021. Retrieved 1 April 2022.
  129. ^ Brown, Mike (2010). How I Killed Pluto and Why It Had It Coming. New York: Spiegel & Grau. ISBN 978-0-385-53108-5. OCLC 495271396.
  130. ^ Carry, B.; et al. (2009). "Physical properties of (2) Pallas". Icarus. 205 (2): 460–472. arXiv:0912.3626. Bibcode:2010Icar..205..460C. doi:10.1016/j.icarus.2009.08.007. S2CID 119194526.
  131. ^ Marsset, M.; Brož, M.; Vernazza, P.; et al. (2020). "The violent collisional history of aqueously evolved (2) Pallas" (PDF). Nature Astronomy. 4 (6): 569–576. Bibcode:2020NatAs...4..569M. doi:10.1038/s41550-019-1007-5. hdl:10261/237549. S2CID 212927521.
  132. ^ "Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta". Space Telescope Science Institute. 19 April 1995. Archived from the original on 20 April 2022. Retrieved 10 April 2022.
  133. ^ Lakdawalla, Emily; et al. (21 April 2020). "What Is A Planet?". The Planetary Society. Archived from the original on 22 January 2022. Retrieved 3 April 2022.
  134. ^ Ferraz-Mello, S. (1994). Milani, Andrea; Di Martino, Michel; Cellino, A. (eds.). Kirkwood Gaps and Resonant Groups. Asteroids, Comets, Meteors 1993: Proceedings of the 160th Symposium of the International Astronomical Union, held in Belgirate, Italy, 14–18 June 1993. Dordrecht: Kluwer Academic Publishers. p. 175. Bibcode:1994IAUS..160..175F.
  135. ^ Snodgrass, Colin; Agarwal, Jessica; Combi, Michael; Fitzsimmons, Alan; Guilbert-Lepoutre, Aurelie; Hsieh, Henry H.; Hui, Man-To; Jehin, Emmanuel; Kelley, Michael S. P.; Knight, Matthew M.; Opitom, Cyrielle (November 2017). "The Main Belt Comets and ice in the Solar System". The Astronomy and Astrophysics Review. 25 (1): 5. arXiv:1709.05549. Bibcode:2017A&ARv..25....5S. doi:10.1007/s00159-017-0104-7. ISSN 0935-4956. S2CID 7683815. Archived from the original on 20 April 2022. Retrieved 9 March 2022.
  136. ^ Barucci, M. A.; Kruikshank, D. P.; Mottola, S.; Lazzarin, M. (2002). "Physical Properties of Trojan and Centaur Asteroids". Asteroids III. Tucson, Arizona: University of Arizona Press. pp. 273–287.
  137. ^ Morbidelli, A.; Bottke, W.F.; Froeschlé, Ch.; Michel, P. (January 2002). W.F. Bottke Jr.; A. Cellino; P. Paolicchi; R.P. Binzel (eds.). "Origin and Evolution of Near-Earth Objects" (PDF). Asteroids III: 409–422. doi:10.2307/j.ctv1v7zdn4.33. Archived (PDF) from the original on 9 August 2017. Retrieved 30 August 2009.
  138. ^ "NEO Basics – Potentially Hazardous Asteroids (PHAs)". CNEOS NASA/JPL. Archived from the original on 11 November 2021. Retrieved 10 March 2022.
  139. ^ "Gas Giant | Planet Types". Exoplanet Exploration: Planets Beyond our Solar System. Archived from the original on 28 November 2020. Retrieved 22 December 2020.
  140. ^ Lissauer, Jack J.; Stevenson, David J. (2006). "Formation of Giant Planets" (PDF). NASA Ames Research Center; California Institute of Technology. Archived from the original (PDF) on 26 March 2009. Retrieved 16 January 2006.
  141. ^ Lewis, John S., ed. (2004). Physics and Chemistry of the Solar System (2nd ed.). Elsevier. p. 147. ISBN 978-0-124-46744-6. OCLC 475009299.
  142. ^ Rogers, John H. (1995). The giant planet Jupiter. Cambridge University Press. p. 293. ISBN 978-0521410083. Archived from the original on 20 April 2022. Retrieved 13 April 2022.
  143. ^ Pappalardo, R. T. (1999). "Geology of the Icy Galilean Satellites: A Framework for Compositional Studies". Brown University. Archived from the original on 30 September 2007. Retrieved 16 January 2006.
  144. ^ Allen, Clabon Walter (2000). Cox, Arthur N. (ed.). Allen's Astrophysical Quantities. Springer. pp. 293–313. ISBN 978-0-387-98746-0. Archived from the original on 1 May 2022. Retrieved 1 May 2022.
  145. ^ "In Depth: Saturn". NASA Science: Solar System Exploration. 18 August 2021. Archived from the original on 24 February 2018. Retrieved 31 March 2022.
  146. ^ Kargel, J. S. (1994). "Cryovolcanism on the icy satellites". Earth, Moon, and Planets. 67 (1–3): 101–113. Bibcode:1995EM&P...67..101K. doi:10.1007/BF00613296. S2CID 54843498. Archived from the original on 10 March 2020. Retrieved 25 August 2019.
  147. ^ "Overview: Titan". NASA Science: Solar System Exploration. 27 June 2019. Archived from the original on 31 March 2022. Retrieved 31 March 2022.
  148. ^ Hörst, Sarah M. (2017). "Titan's Atmosphere and Climate". Journal of Geophysical Research: Planets. 122 (3): 432–482. arXiv:1702.08611. Bibcode:2017JGRE..122..432H. doi:10.1002/2016JE005240. S2CID 119482985.
  149. ^ Devitt, Terry (14 October 2008). "New images yield clues to seasons of Uranus". University of Wisconsin–Madison.
  150. ^ Hawksett, David; Longstaff, Alan; Cooper, Keith; Clark, Stuart (2005). "10 Mysteries of the Solar System". Astronomy Now. 19 (8): 65. Bibcode:2005AsNow..19h..65H.
  151. ^ Williams, Matt (16 December 2014). "What is the average surface temperature of the planets in our solar system?". Archived from the original on 4 March 2021. Retrieved 20 April 2022.
  152. ^ Sheppard, S. S.; Jewitt, D.; Kleyna, J. (2005). "An Ultradeep Survey for Irregular Satellites of Uranus: Limits to Completeness". The Astronomical Journal. 129 (1): 518. arXiv:astro-ph/0410059. Bibcode:2005AJ....129..518S. doi:10.1086/426329. S2CID 18688556.
  153. ^ Leonard, Erin; Elder, Catherine; Nordheim, Tom; Cartwright, Richard; Patthoff, D. Alex; Beddingfield, Chloe; Tiscareno, Matthew; Strange, Nathan; Balint, Tibor (May 2021). "A New Frontiers Class Mission for the Uranian System that Focuses on Moon, Magnetosphere, and Ring Science". Bulletin of the American Astronomical Society. Planetary Science and Astrobiology Decadal Survey 2023–2032 white paper. 53 (4): 176. Bibcode:2021BAAS...53d.176L. doi:10.3847/25c2cfeb.eb4dc2b2. S2CID 236766366. 176.
  154. ^ Podolak, M.; Reynolds, R. T.; Young, R. (1990). "Post Voyager comparisons of the interiors of Uranus and Neptune". Geophysical Research Letters (Submitted manuscript). 17 (10): 1737–1740. Bibcode:1990GeoRL..17.1737P. doi:10.1029/GL017i010p01737. Archived from the original on 1 December 2020. Retrieved 8 September 2020.
  155. ^ Soderblom, L. A.; Kieffer, S. W.; Becker, T. L.; Brown, R. H.; Cook, A. F. II; Hansen, C. J.; Johnson, T. V.; Kirk, R. L.; Shoemaker, E. M. (19 October 1990). "Triton's Geyser-Like Plumes: Discovery and Basic Characterization" (PDF). Science. 250 (4979): 410–415. Bibcode:1990Sci...250..410S. doi:10.1126/science.250.4979.410. PMID 17793016. S2CID 1948948. Archived (PDF) from the original on 31 August 2021. Retrieved 31 March 2022.
  156. ^ Agnor, C. B.; Hamilton, D. P. (2006). "Neptune's capture of its moon Triton in a binary–planet gravitational encounter" (PDF). Nature. 441 (7090): 192–194. Bibcode:2006Natur.441..192A. doi:10.1038/nature04792. PMID 16688170. S2CID 4420518. Archived (PDF) from the original on 14 October 2016. Retrieved 31 March 2022.
  157. ^ Sheppard, Scott S.; Trujillo, Chadwick A. (10 September 2010). "Detection of a Trailing (L5) Neptune Trojan". Science. 329 (5997): 1304. Bibcode:2010Sci...329.1304S. doi:10.1126/science.1189666. ISSN 0036-8075. PMID 20705814. S2CID 7657932.
  158. ^ Vanouplines, Patrick (1995). "Chiron biography". Vrije Universitiet Brussel. Archived from the original on 2 May 2009. Retrieved 23 June 2006.
  159. ^ Stansberry, John; Grundy, Will; Brown, Mike; Cruikshank, Dale; Spencer, John; Trilling, David; Margot, Jean-Luc (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". The Solar System Beyond Neptune. p. 161. arXiv:astro-ph/0702538.
  160. ^ Braga-Ribas, F.; et al. (April 2014). "A ring system detected around the Centaur (10199) Chariklo". Nature. 508 (7494): 72–75. arXiv:1409.7259. Bibcode:2014Natur.508...72B. doi:10.1038/nature13155. ISSN 0028-0836. PMID 24670644. S2CID 4467484.
  161. ^ "In Depth: Comets". NASA Science: Solar System Exploration. 19 December 2019. Archived from the original on 31 March 2022. Retrieved 31 March 2022.
  162. ^ Sekanina, Zdeněk (2001). "Kreutz sungrazers: the ultimate case of cometary fragmentation and disintegration?". Publications of the Astronomical Institute of the Academy of Sciences of the Czech Republic. 89: 78–93. Bibcode:2001PAICz..89...78S.
  163. ^ Królikowska, M. (2001). "A study of the original orbits of hyperbolic comets". Astronomy & Astrophysics. 376 (1): 316–324. Bibcode:2001A&A...376..316K. doi:10.1051/0004-6361:20010945.
  164. ^ Whipple, Fred L. (1992). "The activities of comets related to their aging and origin". Celestial Mechanics and Dynamical Astronomy. 54 (1–3): 1–11. Bibcode:1992CeMDA..54....1W. doi:10.1007/BF00049540. S2CID 189827311.
  165. ^ Stern, Alan (February 2015). "Journey to the Solar System's Third Zone". American Scientist. Archived from the original on 26 October 2018. Retrieved 26 October 2018.
  166. ^ a b Tegler, Stephen C. (2007). "Kuiper Belt Objects: Physical Studies". In Lucy-Ann McFadden; et al. (eds.). Encyclopedia of the Solar System. p. 605–620. ISBN 978-0120885893.
  167. ^ a b Grundy, W. M.; Noll, K. S.; Buie, M. W.; Benecchi, S. D.; Ragozzine, D.; Roe, H. G. (December 2018). "The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)" (PDF). Icarus. 334: 30–38. doi:10.1016/j.icarus.2018.12.037. S2CID 126574999. Archived from the original on 7 April 2019.
  168. ^ Brown, M.E.; Van Dam, M.A.; Bouchez, A.H.; Le Mignant, D.; Campbell, R.D.; Chin, J.C.Y.; Conrad, A.; Hartman, S.K.; Johansson, E.M.; Lafon, R.E.; Rabinowitz, D.L. Rabinowitz; Stomski, P.J. Jr.; Summers, D.M.; Trujillo, C.A.; Wizinowich, P.L. (2006). "Satellites of the Largest Kuiper Belt Objects" (PDF). The Astrophysical Journal. 639 (1): L43–L46. arXiv:astro-ph/0510029. Bibcode:2006ApJ...639L..43B. doi:10.1086/501524. S2CID 2578831. Archived (PDF) from the original on 28 September 2018. Retrieved 19 October 2011.
  169. ^ Chiang, E.I.; Jordan, A.B.; Millis, R.L.; Buie, M.W.; Wasserman, L.H.; Elliot, J.L.; Kern, S.D.; Trilling, D.E.; Meech, K.J.; et al. (2003). "Resonance Occupation in the Kuiper Belt: Case Examples of the 5:2 and Trojan Resonances" (PDF). The Astronomical Journal. 126 (1): 430–443. arXiv:astro-ph/0301458. Bibcode:2003AJ....126..430C. doi:10.1086/375207. S2CID 54079935. Archived (PDF) from the original on 15 March 2016. Retrieved 15 August 2009.
  170. ^ Buie, M. W.; Millis, R. L.; Wasserman, L. H.; Elliot, J. L.; Kern, S. D.; Clancy, K. B.; Chiang, E. I.; Jordan, A. B.; Meech, K. J.; Wagner, R. M.; Trilling, D. E. (2005). "Procedures, Resources and Selected Results of the Deep Ecliptic Survey". Earth, Moon, and Planets. 92 (1): 113–124. arXiv:astro-ph/0309251. Bibcode:2003EM&P...92..113B. doi:10.1023/ S2CID 14820512.
  171. ^ Dotto, E.; Barucci, M. A.; Fulchignoni, M. (1 January 2003). "Beyond Neptune, the new frontier of the Solar System" (PDF). Memorie della Societa Astronomica Italiana Supplementi. 3: 20. Bibcode:2003MSAIS...3...20D. ISSN 0037-8720. Archived (PDF) from the original on 25 August 2014. Retrieved 26 December 2006.
  172. ^ Emery, J. P.; Wong, I.; Brunetto, R.; Cook, J. C.; Pinilla-Alonso, N.; Stansberry, J. A.; Holler, B. J.; Grundy, W. M.; Protopapa, S.; Souza-Feliciano, A. C.; Fernández-Valenzuela, E.; Lunine, J. I.; Hines, D. C. (2024). "A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar from JWST Spectroscopy". Icarus. 414. arXiv:2309.15230. Bibcode:2024Icar..41416017E. doi:10.1016/j.icarus.2024.116017.
  173. ^ Tancredi, G.; Favre, S. A. (2008). "Which are the dwarfs in the Solar System?". Icarus. 195 (2): 851–862. Bibcode:2008Icar..195..851T. doi:10.1016/j.icarus.2007.12.020.
  174. ^ Fajans, J.; Frièdland, L. (October 2001). "Autoresonant (nonstationary) excitation of pendulums, Plutinos, plasmas, and other nonlinear oscillators" (PDF). American Journal of Physics. 69 (10): 1096–1102. Bibcode:2001AmJPh..69.1096F. doi:10.1119/1.1389278. Archived from the original (PDF) on 7 June 2011. Retrieved 26 December 2006.
  175. ^ "In Depth: Pluto". NASA Science: Solar System Exploration. 6 August 2021. Archived from the original on 31 March 2022. Retrieved 31 March 2022.
  176. ^ "Fourth dwarf planet named Makemake". International Astronomical Union. 19 July 2009. Archived from the original on 30 July 2017. Retrieved 9 April 2022.
  177. ^ Buie, Marc W. (5 April 2008). "Orbit Fit and Astrometric record for 136472". SwRI (Space Science Department). Archived from the original on 27 May 2020. Retrieved 15 July 2012.
  178. ^ Parker, A. H.; Buie, M. W.; Grundy, W. M.; Noll, K. S. (25 April 2016). "Discovery of a Makemakean Moon". The Astrophysical Journal. 825 (1): L9. arXiv:1604.07461. Bibcode:2016ApJ...825L...9P. doi:10.3847/2041-8205/825/1/L9. S2CID 119270442.
  179. ^ a b c Brown, Mike (2008). "The largest Kuiper belt objects" (PDF). In Barucci, M. Antonietta (ed.). The Solar System Beyond Neptune. University of Arizona Press. pp. 335–344. ISBN 978-0-816-52755-7. OCLC 1063456240. Archived (PDF) from the original on 13 November 2012. Retrieved 9 April 2022.
  180. ^ "IAU names fifth dwarf planet Haumea". International Astronomical Union. 17 September 2008. Archived from the original on 25 April 2014. Retrieved 9 April 2022.
  181. ^ Noviello, Jessica L.; Desch, Stephen J.; Neveu, Marc; Proudfoot, Benjamin C. N.; Sonnett, Sarah (September 2022). "Let It Go: Geophysically Driven Ejection of the Haumea Family Members". The Planetary Science Journal. 3 (9): 19. Bibcode:2022PSJ.....3..225N. doi:10.3847/PSJ/ac8e03. S2CID 252620869. 225.
  182. ^ B. E. Morgado; et al. (8 February 2023). "A dense ring of the trans-Neptunian object Quaoar outside its Roche limit". Nature. 614 (7947): 239–243. Bibcode:2023Natur.614..239M. doi:10.1038/S41586-022-05629-6. ISSN 1476-4687. Wikidata Q116754015.
  183. ^ "MPEC 2004-D15 : 2004 DW". Minor Planet Center. 20 February 2004. Archived from the original on 3 March 2016. Retrieved 5 July 2011.
  184. ^ Michael E. Brown (23 March 2009). "S/2005 (90482) 1 needs your help". Mike Brown's Planets (blog). Archived from the original on 28 March 2009. Retrieved 25 March 2009.
  185. ^ Moltenbrey, Michael (2016). Dawn of Small Worlds: Dwarf planets, asteroids, comets. Cham: Springer. p. 171. ISBN 978-3-319-23003-0. OCLC 926914921. Archived from the original on 20 April 2022. Retrieved 9 April 2022.
  186. ^ Green, Daniel W. E. (22 February 2007). "IAUC 8812: Sats OF 2003 AZ_84, (50000), (55637),, (90482)". International Astronomical Union Circular. Archived from the original on 14 March 2012. Retrieved 4 July 2011.
  187. ^ Gomes, R. S.; Fernández, J. A.; Gallardo, T.; Brunini, A. (2008). "The Scattered Disk: Origins, Dynamics, and End States". The Solar System Beyond Neptune (PDF). University of Arizona Press. pp. 259–273. ISBN 978-0816527557. Archived (PDF) from the original on 21 January 2022. Retrieved 12 May 2022.
  188. ^ Jewitt, David (2005). "The 1,000 km Scale KBOs". University of Hawaii. Archived from the original on 9 June 2014. Retrieved 16 July 2006.
  189. ^ "List of Centaurs and Scattered-Disk Objects". IAU: Minor Planet Center. Archived from the original on 29 June 2017. Retrieved 2 April 2007.
  190. ^ Brown, Michael E.; Schaller, Emily L. (15 June 2007). "The Mass of Dwarf Planet Eris". Science. 316 (5831): 1585. Bibcode:2007Sci...316.1585B. doi:10.1126/science.1139415. PMID 17569855. S2CID 21468196.
  191. ^ Dumas, C.; Merlin, F.; Barucci, M. A.; de Bergh, C.; Hainault, O.; Guilbert, A.; Vernazza, P.; Doressoundiram, A. (August 2007). "Surface composition of the largest dwarf planet 136199 Eris (2003 UB{313})". Astronomy and Astrophysics. 471 (1): 331–334. Bibcode:2007A&A...471..331D. doi:10.1051/0004-6361:20066665.
  192. ^ "JPL Small-Body Database Browser: 225088 Gonggong (2007 OR10)" (20 September 2015 last obs.). Jet Propulsion Laboratory. 10 April 2017. Archived from the original on 10 June 2020. Retrieved 20 February 2020.
  193. ^ Kiss, Csaba; Marton, Gábor; Farkas-Takács, Anikó; Stansberry, John; Müller, Thomas; Vinkó, József; Balog, Zoltán; Ortiz, Jose-Luis; Pál, András (16 March 2017). "Discovery of a Satellite of the Large Trans-Neptunian Object (225088) 2007 OR10". The Astrophysical Journal Letters. 838 (1): 5. arXiv:1703.01407. Bibcode:2017ApJ...838L...1K. doi:10.3847/2041-8213/aa6484. S2CID 46766640. L1.
  194. ^ Littmann, Mark (2004). Planets Beyond: Discovering the Outer Solar System. Courier Dover Publications. pp. 162–163. ISBN 978-0-486-43602-9.
  195. ^ a b c Fahr, H. J.; Kausch, T.; Scherer, H. (2000). "A 5-fluid hydrodynamic approach to model the Solar System-interstellar medium interaction" (PDF). Astronomy & Astrophysics. 357: 268. Bibcode:2000A&A...357..268F. Archived from the original (PDF) on 8 August 2017. Retrieved 24 August 2008. See Figures 1 and 2.
  196. ^ Hatfield, Miles (3 June 2021). "The Heliopedia". NASA. Archived from the original on 25 March 2022. Retrieved 29 March 2022.
  197. ^ Baranov, V. B.; Malama, Yu. G. (1993). "Model of the solar wind interaction with the local interstellar medium: Numerical solution of self-consistent problem". Journal of Geophysical Research. 98 (A9): 15157. Bibcode:1993JGR....9815157B. doi:10.1029/93JA01171. ISSN 0148-0227. Retrieved 9 April 2022.
  198. ^ "Cassini's Big Sky: The View from the Center of Our Solar System". Jet Propulsion Laboratory. 19 November 2009. Archived from the original on 9 April 2022. Retrieved 9 April 2022.
  199. ^ Kornbleuth, M.; Opher, M.; Baliukin, I.; Gkioulidou, M.; Richardson, J. D.; Zank, G. P.; Michael, A. T.; Tóth, G.; Tenishev, V.; Izmodenov, V.; Alexashov, D. (1 December 2021). "The Development of a Split-tail Heliosphere and the Role of Non-ideal Processes: A Comparison of the BU and Moscow Models". The Astrophysical Journal. 923 (2): 179. arXiv:2110.13962. Bibcode:2021ApJ...923..179K. doi:10.3847/1538-4357/ac2fa6. ISSN 0004-637X. S2CID 239998560.
  200. ^ Reisenfeld, Daniel B.; Bzowski, Maciej; Funsten, Herbert O.; Heerikhuisen, Jacob; Janzen, Paul H.; Kubiak, Marzena A.; McComas, David J.; Schwadron, Nathan A.; Sokół, Justyna M.; Zimorino, Alex; Zirnstein, Eric J. (1 June 2021). "A Three-dimensional Map of the Heliosphere from IBEX". The Astrophysical Journal Supplement Series. 254 (2): 40. Bibcode:2021ApJS..254...40R. doi:10.3847/1538-4365/abf658. ISSN 0067-0049. OSTI 1890983. S2CID 235400678.
  201. ^ Stone, E. C.; Cummings, A. C.; McDonald, F. B.; Heikkila, B. C.; Lal, N.; Webber, W. R. (September 2005). "Voyager 1 explores the termination shock region and the heliosheath beyond". Science. 309 (5743): 2017–2020. Bibcode:2005Sci...309.2017S. doi:10.1126/science.1117684. PMID 16179468. S2CID 34517751.
  202. ^ Stone, E. C.; Cummings, A. C.; McDonald, F. B.; Heikkila, B. C.; Lal, N.; Webber, W. R. (July 2008). "An asymmetric solar wind termination shock". Nature. 454 (7200): 71–74. Bibcode:2008Natur.454...71S. doi:10.1038/nature07022. PMID 18596802. S2CID 4431329.
  203. ^ Cook, Jia-Rui C.; Agle, D. C.; Brown, Dwayne (12 September 2013). "NASA Spacecraft Embarks on Historic Journey into Interstellar Space". NASA. Archived from the original on 11 June 2020. Retrieved 12 September 2013.
  204. ^ Lakdawalla, Emily (10 December 2018). "News brief: Voyager 2 has passed beyond the heliopause". The Planetary Society. Archived from the original on 15 June 2021. Retrieved 10 April 2022.
  205. ^ Nemiroff, R.; Bonnell, J., eds. (24 June 2002). "The Sun's Heliosphere & Heliopause". Astronomy Picture of the Day. NASA. Retrieved 23 June 2006.
  206. ^ Jewitt, David (2004). "Sedna – 2003 VB12". University of Hawaii. Archived from the original on 16 July 2011. Retrieved 23 June 2006.
  207. ^ Brown, Mike (2004). "Sedna". Caltech. Archived from the original on 25 July 2010. Retrieved 2 May 2007.
  208. ^ "JPL Small-Body Database Browser: (2012 VP113)" (2020-02-05 last obs). Jet Propulsion Laboratory. Archived from the original on 20 April 2020. Retrieved 29 March 2022.
  209. ^ Witze, Alexandra (26 March 2014). "Dwarf planet stretches Solar System's edge". Nature. doi:10.1038/nature.2014.14921. S2CID 124305879.
  210. ^ Encrenaz, T.; Bibring, J. P.; Blanc, M.; Barucci, M. A.; Roques, F.; Zarka, P. H. (2004). The Solar System (3rd ed.). Springer. p. 1.
  211. ^ Torres, S.; Cai, M. X.; Brown, A. G. A.; Portegies Zwart, S. (September 2019). "Galactic tide and local stellar perturbations on the Oort cloud: creation of interstellar comets". Astronomy & Astrophysics. 629: 13. arXiv:1906.10617. Bibcode:2019A&A...629A.139T. doi:10.1051/0004-6361/201935330. S2CID 195584070. A139.
  212. ^ Norman, Neil (May 2020). "10 great comets of recent times". BBC Sky at Night Magazine. Archived from the original on 25 January 2022. Retrieved 10 April 2022.
  213. ^ Bernardinelli, Pedro H.; Bernstein, Gary M.; Montet, Benjamin T.; et al. (1 November 2021). "C/2014 UN 271 (Bernardinelli-Bernstein): The Nearly Spherical Cow of Comets". The Astrophysical Journal Letters. 921 (2): L37. arXiv:2109.09852. Bibcode:2021ApJ...921L..37B. doi:10.3847/2041-8213/ac32d3. ISSN 2041-8205. S2CID 237581632.
  214. ^ Loeffler, John (1 October 2021). "Our solar system may have a hidden planet beyond Neptune – no, not that one". MSN. Archived from the original on 1 October 2021. Retrieved 7 April 2022.
  215. ^ a b Stern SA, Weissman PR (2001). "Rapid collisional evolution of comets during the formation of the Oort cloud". Nature. 409 (6820): 589–591. Bibcode:2001Natur.409..589S. doi:10.1038/35054508. PMID 11214311. S2CID 205013399.
  216. ^ a b Arnett, Bill (2006). "The Kuiper Belt and the Oort Cloud". Nine Planets. Archived from the original on 7 August 2019. Retrieved 23 June 2006.
  217. ^ "Oort Cloud". NASA Solar System Exploration. Archived from the original on 30 June 2023. Retrieved 1 July 2023.
  218. ^ Batygin, Konstantin; Adams, Fred C.; Brown, Michael E.; Becker, Juliette C. (2019). "The Planet Nine Hypothesis". Physics Reports. 805: 1–53. arXiv:1902.10103. Bibcode:2019PhR...805....1B. doi:10.1016/j.physrep.2019.01.009. S2CID 119248548.
  219. ^ Trujillo, Chadwick A.; Sheppard, Scott S. (2014). "A Sedna-like Body with a Perihelion of 80 Astronomical Units" (PDF). Nature. 507 (7493): 471–474. Bibcode:2014Natur.507..471T. doi:10.1038/nature13156. PMID 24670765. S2CID 4393431. Archived from the original (PDF) on 16 December 2014. Retrieved 20 January 2016.
  220. ^ Napier, K. J. (2021). "No Evidence for Orbital Clustering in the Extreme Trans-Neptunian Objects". The Planetary Science Journal. 2 (2): 59. arXiv:2102.05601. Bibcode:2021PSJ.....2...59N. doi:10.3847/PSJ/abe53e.
  221. ^ Swaczyna, Paweł; Schwadron, Nathan A.; Möbius, Eberhard; Bzowski, Maciej; Frisch, Priscilla C.; Linsky, Jeffrey L.; McComas, David J.; Rahmanifard, Fatemeh; Redfield, Seth; Winslow, Réka M.; Wood, Brian E.; Zank, Gary P. (1 October 2022). "Mixing Interstellar Clouds Surrounding the Sun". The Astrophysical Journal Letters. 937 (2): L32:1–2. arXiv:2209.09927. Bibcode:2022ApJ...937L..32S. doi:10.3847/2041-8213/ac9120. ISSN 2041-8205.
  222. ^ "Our Local Galactic Neighborhood". NASA. 5 June 2013. Archived from the original on 21 November 2013.
  223. ^ a b Linsky, Jeffrey L.; Redfield, Seth; Tilipman, Dennis (20 November 2019). "The Interface between the Outer Heliosphere and the Inner Local ISM: Morphology of the Local Interstellar Cloud, Its Hydrogen Hole, Strömgren Shells, and 60 Fe Accretion*". The Astrophysical Journal. 886 (1): 41. arXiv:1910.01243. Bibcode:2019ApJ...886...41L. doi:10.3847/1538-4357/ab498a. ISSN 0004-637X. S2CID 203642080.
  224. ^ Zucker, Catherine; Goodman, Alyssa A.; Alves, João; et al. (January 2022). "Star formation near the Sun is driven by expansion of the Local Bubble". Nature. 601 (7893): 334–337. arXiv:2201.05124. Bibcode:2022Natur.601..334Z. doi:10.1038/s41586-021-04286-5. ISSN 1476-4687. PMID 35022612. S2CID 245906333. Archived from the original on 17 April 2022. Retrieved 1 April 2022.
  225. ^ Alves, João; Zucker, Catherine; Goodman, Alyssa A.; Speagle, Joshua S.; Meingast, Stefan; Robitaille, Thomas; Finkbeiner, Douglas P.; Schlafly, Edward F.; Green, Gregory M. (23 January 2020). "A Galactic-scale gas wave in the Solar Neighborhood". Nature. 578 (7794): 237–239. arXiv:2001.08748v1. Bibcode:2020Natur.578..237A. doi:10.1038/s41586-019-1874-z. PMID 31910431. S2CID 210086520.
  226. ^ McKee, Christopher F.; Parravano, Antonio; Hollenbach, David J. (November 2015). "Stars, Gas, and Dark Matter in the Solar Neighborhood". The Astrophysical Journal. 814 (1): 24. arXiv:1509.05334. Bibcode:2015ApJ...814...13M. doi:10.1088/0004-637X/814/1/13. S2CID 54224451. 13.
  227. ^ Linsky, Jeffrey L.; Redfield, Seth; Tilipman, Dennis (November 2019). "The Interface between the Outer Heliosphere and the Inner Local ISM: Morphology of the Local Interstellar Cloud, Its Hydrogen Hole, Strömgren Shells, and 60Fe Accretion". The Astrophysical Journal. 886 (1): 19. arXiv:1910.01243. Bibcode:2019ApJ...886...41L. doi:10.3847/1538-4357/ab498a. S2CID 203642080. 41.
  228. ^ Anglada-Escudé, Guillem; Amado, Pedro J.; Barnes, John; et al. (2016). "A terrestrial planet candidate in a temperate orbit around Proxima Centauri". Nature. 536 (7617): 437–440. arXiv:1609.03449. Bibcode:2016Natur.536..437A. doi:10.1038/nature19106. PMID 27558064. S2CID 4451513. Archived from the original on 3 October 2021. Retrieved 11 September 2021.
  229. ^ "The One Hundred Nearest Star Systems". Georgia State University Astronomy Department. Research Consortium on Nearby Stars (RECONS). 17 September 2007. Archived from the original on 12 November 2007. Retrieved 1 May 2022.
  230. ^ Luhman, K. L. (2014). "Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun". The Astrophysical Journal. 786 (2): L18. arXiv:1404.6501. Bibcode:2014ApJ...786L..18L. doi:10.1088/2041-8205/786/2/L18. S2CID 119102654.
  231. ^ Karttunen, Hannu; Oja, Heikki; Donner, Karl Johan; Poutanen, Markku; Kröger, Pekka, eds. (2003). Fundamental Astronomy (4th ed.). Berlin: Springer. p. 414. ISBN 978-3-540-00179-9. OCLC 51003837. Archived from the original on 20 April 2022. Retrieved 1 April 2022.
  232. ^ van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  233. ^ Teixeira, T. C.; Kjeldsen, H.; Bedding, T. R.; Bouchy, F.; Christensen-Dalsgaard, J.; Cunha, M. S.; et al. (January 2009). "Solar-like oscillations in the G8 V star τ Ceti". Astronomy and Astrophysics. 494 (1): 237–242. arXiv:0811.3989. Bibcode:2009A&A...494..237T. doi:10.1051/0004-6361:200810746. S2CID 59353134.
  234. ^ Alves, João; Zucker, Catherine; Goodman, Alyssa A.; et al. (2020). "A Galactic-scale gas wave in the solar neighborhood". Nature. 578 (7794): 237–239. arXiv:2001.08748. Bibcode:2020Natur.578..237A. doi:10.1038/s41586-019-1874-z. PMID 31910431. S2CID 210086520.
  235. ^ a b Lang, Kenneth R. (2013). The Life and Death of Stars. Cambridge University Press. p. 264. ISBN 978-1107016385. Archived from the original on 20 April 2022. Retrieved 8 April 2022.
  236. ^ Drimmel, R.; Spergel, D. N. (2001). "Three Dimensional Structure of the Milky Way Disk". The Astrophysical Journal. 556 (1): 181–202. arXiv:astro-ph/0101259. Bibcode:2001ApJ...556..181D. doi:10.1086/321556. S2CID 15757160.
  237. ^ Gerhard, O. (2011). "Pattern speeds in the Milky Way". Memorie della Societa Astronomica Italiana, Supplementi. 18: 185. arXiv:1003.2489. Bibcode:2011MSAIS..18..185G.
  238. ^ Leong, Stacy (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". The Physics Factbook. Archived from the original on 7 January 2019. Retrieved 2 April 2007.
  239. ^ Greiner, Walter (2004). Classical Mechanics: Point particles and relativity. New York: Springer. p. 323. ISBN 978-0-387-21851-9. OCLC 56727455. Archived from the original on 20 April 2022. Retrieved 29 March 2022.
  240. ^ Reid, M. J.; Brunthaler, A. (2004). "The Proper Motion of Sagittarius A*". The Astrophysical Journal. 616 (2): 872–884. arXiv:astro-ph/0408107. Bibcode:2004ApJ...616..872R. doi:10.1086/424960. S2CID 16568545.
  241. ^ a b c Mullen, Leslie (18 May 2001). "Galactic Habitable Zones". Astrobiology Magazine. Archived from the original on 7 August 2011. Retrieved 1 June 2020.
  242. ^ Bailer-Jones, C. A. L. (1 July 2009). "The evidence for and against astronomical impacts on climate change and mass extinctions: a review". International Journal of Astrobiology. 8 (3): 213–219. arXiv:0905.3919. Bibcode:2009IJAsB...8..213B. doi:10.1017/S147355040999005X. S2CID 2028999. Archived from the original on 1 April 2022. Retrieved 1 April 2022.
  243. ^ Racki, Grzegorz (December 2012). "The Alvarez Impact Theory of Mass Extinction; Limits to its Applicability and the "Great Expectations Syndrome"". Acta Palaeontologica Polonica. 57 (4): 681–702. doi:10.4202/app.2011.0058. hdl:20.500.12128/534. ISSN 0567-7920. S2CID 54021858. Archived from the original on 1 April 2022. Retrieved 1 April 2022.
  244. ^ Abuter, R.; Amorim, A.; Bauböck, M.; Berger, J. P.; Bonnet, H.; Brandner, W.; et al. (May 2019). "A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty". Astronomy & Astrophysics. 625: L10. arXiv:1904.05721. Bibcode:2019A&A...625L..10G. doi:10.1051/0004-6361/201935656. ISSN 0004-6361. S2CID 119190574. Archived from the original on 20 April 2022. Retrieved 1 April 2022.
  245. ^ Mamajek, Eric E.; Barenfeld, Scott A.; Ivanov, Valentin D.; Kniazev, Alexei Y.; Väisänen, Petri; Beletsky, Yuri; Boffin, Henri M. J. (February 2015). "The Closest Known Flyby of a Star to the Solar System". The Astrophysical Journal Letters. 800 (1): 4. arXiv:1502.04655. Bibcode:2015ApJ...800L..17M. doi:10.1088/2041-8205/800/1/L17. S2CID 40618530. L17.
  246. ^ Raymond, Sean N.; et al. (January 2024). "Future trajectories of the Solar System: dynamical simulations of stellar encounters within 100 au". Monthly Notices of the Royal Astronomical Society. 527 (3): 6126–6138. arXiv:2311.12171. Bibcode:2024MNRAS.527.6126R. doi:10.1093/mnras/stad3604.
  247. ^ Orrell, David (2012). Truth Or Beauty: Science and the Quest for Order. Yale University Press. pp. 25–27. ISBN 978-0300186611. Archived from the original on 30 July 2022. Retrieved 13 May 2022.
  248. ^ Rufus, W. C. (1923). "The astronomical system of Copernicus". Popular Astronomy. Vol. 31. p. 510. Bibcode:1923PA.....31..510R.
  249. ^ Weinert, Friedel (2009). Copernicus, Darwin, & Freud: revolutions in the history and philosophy of science. Wiley-Blackwell. p. 21. ISBN 978-1-4051-8183-9.
  250. ^ LoLordo, Antonia (2007). Pierre Gassendi and the Birth of Early Modern Philosophy. New York: Cambridge University Press. pp. 12, 27. ISBN 978-0-511-34982-9. OCLC 182818133. Archived from the original on 20 April 2022. Retrieved 1 April 2022.
  251. ^ Athreya, A.; Gingerich, O. (December 1996). "An Analysis of Kepler's Rudolphine Tables and Implications for the Reception of His Physical Astronomy". Bulletin of the American Astronomical Society. 28 (4): 1305. Bibcode:1996AAS...189.2404A.
  252. ^ Pasachoff, Jay M. (May 2015). "Simon Marius's Mundus Iovialis: 400th Anniversary in Galileo's Shadow". Journal for the History of Astronomy. 46 (2): 218–234. Bibcode:2015JHA....46..218P. doi:10.1177/0021828615585493. ISSN 0021-8286. S2CID 120470649. Archived from the original on 27 November 2021. Retrieved 1 April 2022.
  253. ^ "Christiaan Huygens: Discoverer of Titan". ESA Space Science. The European Space Agency. 8 December 2012. Archived from the original on 6 December 2019. Retrieved 27 October 2010.
  254. ^ Chapman, Allan (April 2005). Kurtz, D. W. (ed.). Jeremiah Horrocks, William Crabtree, and the Lancashire observations of the transit of Venus of 1639. Transits of Venus: New Views of the Solar System and Galaxy, Proceedings of IAU Colloquium #196, held 7–11 June 2004 in Preston, U.K. Proceedings of the International Astronomical Union. Vol. 2004. Cambridge: Cambridge University Press. pp. 3–26. Bibcode:2005tvnv.conf....3C. doi:10.1017/S1743921305001225.
  255. ^ See, for example:
  256. ^ Festou, M. C.; Keller, H. U.; Weaver, H. A. (2004). "A brief conceptual history of cometary science". Comets II. Tucson: University of Arizona Press. pp. 3–16. ISBN 978-0816524501. Archived from the original on 20 April 2022. Retrieved 7 April 2022.
  257. ^ Sagan, Carl; Druyan, Ann (1997). Comet. New York: Random House. pp. 26–27, 37–38. ISBN 978-0-3078-0105-0. Archived from the original on 15 June 2021. Retrieved 28 June 2021.
  258. ^ Teets, Donald (December 2003). "Transits of Venus and the Astronomical Unit" (PDF). Mathematics Magazine. 76 (5): 335–348. doi:10.1080/0025570X.2003.11953207. JSTOR 3654879. S2CID 54867823. Archived (PDF) from the original on 3 February 2022. Retrieved 3 April 2022.
  259. ^ Bourtembourg, René (2013). "Was Uranus Observed by Hipparchos?". Journal for the History of Astronomy. 44 (4): 377–387. Bibcode:2013JHA....44..377B. doi:10.1177/002182861304400401. S2CID 122482074.
  260. ^ Di Bari, Pasquale (2018). Cosmology and the Early Universe. CRC Press. pp. 3–4. ISBN 978-1351020138.
  261. ^ Bhatnagar, Siddharth; Vyasanakere, Jayanth P.; Murthy, Jayant (May 2021). "A geometric method to locate Neptune". American Journal of Physics. 89 (5): 454–458. arXiv:2102.04248. Bibcode:2021AmJPh..89..454B. doi:10.1119/10.0003349. ISSN 0002-9505. S2CID 231846880. Archived from the original on 29 November 2021. Retrieved 1 April 2022.
  262. ^ Clemence, G. M. (1947). "The Relativity Effect in Planetary Motions". Reviews of Modern Physics. 19 (4): 361–364. Bibcode:1947RvMP...19..361C. doi:10.1103/RevModPhys.19.361. (math)
  263. ^ Garner, Rob (10 December 2018). "50th Anniversary of OAO 2: NASA's 1st Successful Stellar Observatory". NASA. Archived from the original on 29 December 2021. Retrieved 20 April 2022.
  264. ^ "Fact Sheet". JPL. Archived from the original on 29 November 2016. Retrieved 3 March 2016.
  265. ^ Woo, Marcus (20 November 2014). "This Is What It Sounded Like When We Landed on a Comet". Wired. Archived from the original on 23 November 2014. Retrieved 20 April 2022.
  266. ^ Marks, Paul (3 December 2014). "Hayabusa 2 probe begins journey to land on an asteroid". New Scientist. Archived from the original on 11 February 2022. Retrieved 20 April 2022.
  267. ^ "NASA's Parker Solar Probe becomes first spacecraft to 'touch' the sun". CNN. 14 December 2021. Archived from the original on 14 December 2021. Retrieved 15 December 2021.
  268. ^ Corum, Jonathan; Gröndahl, Mika; Parshina-Kottas, Yuliya (13 July 2015). "New Horizons' Pluto Flyby". The New York Times. ISSN 0362-4331. Retrieved 20 April 2022.
  269. ^ McCartney, Gretchen; Brown, Dwayne; Wendel, JoAnna (7 September 2018). "Legacy of NASA's Dawn, Near the End of its Mission". NASA. Retrieved 8 September 2018.
  270. ^ Glenday, Craig, ed. (2010). Guinness World Records 2010. New York: Bantam Books. ISBN 978-0-553-59337-2.
  271. ^ Foust, Jeff (13 March 2023). "NASA planning to spend up to $1 billion on space station deorbit module". SpaceNews. Retrieved 13 March 2023.
  272. ^ Chang, Kenneth (18 January 2022). "Quiz - Is Pluto A Planet? - Who doesn't love Pluto? It shares a name with the Roman god of the underworld and a Disney dog. But is it a planet? - Interactive". The New York Times. Retrieved 18 January 2022.
  273. ^ Spaceflight, Leonard David (9 January 2019). "A Wild 'Interstellar Probe' Mission Idea Is Gaining Momentum". Retrieved 23 September 2019.

External links

Listen to this article (1 hour and 2 minutes)
Spoken Wikipedia icon
This audio file was created from a revision of this article dated 31 May 2021 (2021-05-31), and does not reflect subsequent edits.