WD 0806−661 B
 JWST image of WD 0806−661 B and its white dwarf star | |
| Discovery[1] | |
|---|---|
| Discovered by | Luhman et al. |
| Discovery date | 2011 |
| Direct imaging | |
| Designations | |
| Ahra, GJ 3483 B | |
| Orbital characteristics | |
| 2,500 AU | |
| Star | WD 0806−661 |
| Physical characteristics | |
| 1.12 RJ | |
| Mass | 7-9 MJ |
| 16.17 g (Estimate) | |
| Temperature | 325-350 K |
WD 0806-661 B, formally named Ahra, is a planetary-mass companion of the white dwarf star WD 0806−661, or Maru.
This object was discovered in 2011 by the Spitzer Space Telescope. It has a mass of between 7-9 MJ, putting it as a gas giant planet. At the time of its discovery, WD 0806-661 b was the coldest brown dwarf ever discovered, with a temperature of 325-350 Kelvin (52-77 °C or 125-170 °F)[2] and also had the largest separation from its star at about 2,500 AU at the time of its discovery. The photometric colors of the object suggest it is metal-poor.[3]
As of 2021, WD 0806-661 b is a potential target for study from the James Webb Space Telescope.[4]
Host star
[edit]WD 0806−661, or Maru, is a white dwarf star of the spectral type DQ. The metal-poor composition of its planetary-mass companion could explain its spectral type, as it is theorized that hydrogen-deficient stars of the asymptotic giant branch could evolve into white dwarfs of spectral type DB and then DQ as they cool down.[5] WD 0806-661 is estimated to be 1.5-2.7 billion years old,[6] and likely used to be an A-type main sequence star of 2.1 ± 0.3 solar masses before reaching the end of its life and becoming a white dwarf.[7] WD 0806-661 B may have formed closer to the star, but migrated further away as it reached the end of its life.
Characteristics
[edit]Because it orbits very far away from its star, WD 0806−661 B is likely very dark, receiving almost no light from its star. However, due to the object's high mass, internal heat keeps the temperature hotter than that of Earth.[2] The object's radius is estimated to be 12% larger than that of Jupiter,[8] and is likely the same age as the star. Despite having temperatures comparable to that of Earth, WD 0806−661 B is a poor candidate for extraterrestrial life due to high surface gravity and lack of starlight. Because of its large mass and distance from its star, WD 0806−661 B could host many large exomoons.
The WD 0806−661 system is planned to be studied by the James Webb Space Telescope, which will probe the atmosphere of the object, as well as search for other planetary-mass bodies in the system.
Type of object
[edit]There is no consensus as to whether WD 0806-661 b should be considered an exoplanet or a sub-brown dwarf. Based on its large distance from the white dwarf, this object likely formed like a star rather than in a protoplanetary disk, and it is generally described as a brown dwarf in the scientific literature.[9] However, the IAU considers objects below the ~13 MJ limiting mass for deuterium fusion that orbit stars (or stellar remnants), with M2/M1[a] < 1/25 to be planets, no matter how they formed.[10] Additionally, WD 0806-661 b has been named Ahra through the IAU's NameExoWorlds exoplanet naming campaign,[11] and is included in databases such as the NASA Exoplanet Archive.[12]
See also
[edit]- WD 0806−661
- COCONUTS-2b - Another planetary-mass companion with a large separation from its star
- List of Y-dwarfs
Notes
[edit]- ^ Mass ratio between planet (M2) and host star (M1)
References
[edit]- ^ Luhman, K. L.; Burgasser, A. J.; Bochanski, J. J. (March 2011). "Discovery of a Candidate for the Coolest Known Brown Dwarf". The Astrophysical Journal Letters. 730 (1): L9. arXiv:1102.5411. Bibcode:2011ApJ...730L...9L. doi:10.1088/2041-8205/730/1/L9. ISSN 2041-8205.
- ^ a b Leggett, S. K.; Tremblin, P.; Esplin, T. L.; Luhman, K. L.; Morley, Caroline V. (2017-06-21). "The Y-Type Brown Dwarfs: Estimates of Mass and Age from New Astrometry, Homogenized Photometry and Near-Infrared Spectroscopy". The Astrophysical Journal. 842 (2): 118. arXiv:1704.03573. doi:10.3847/1538-4357/aa6fb5. ISSN 1538-4357.
- ^ "_13428". _13428. doi:10.5270/esa-4bo1j7l. Retrieved 2023-09-09.
- ^ "1276 - Spectroscopic Observations of WD 0806-661B" (PDF).
- ^ Camisassa, María E.; Althaus, Leandro G.; Rohrmann, René D.; García-Berro, Enrique; Torres, Santiago; Córsico, Alejandro H.; Wachlin, Felipe C. (April 2017). "Updated Evolutionary Sequences for Hydrogen-deficient White Dwarfs". The Astrophysical Journal. 839 (1): 11. doi:10.3847/1538-4357/aa6797. hdl:11336/63304. ISSN 0004-637X.
- ^ "The Extrasolar Planet Encyclopaedia — WD 0806-661 B b". Extrasolar Planets Encyclopaedia. Retrieved 2023-09-09.
- ^ Luhman, Kevin; Burgasser, Adam; Bochanski, John (2011-01-01). "Confirmation of a Candidate for the Coolest Known Brown Dwarf". Spitzer Proposal: 70203. Bibcode:2011sptz.prop70203L.
- ^ "Exoplanet-catalog". Exoplanet Exploration: Planets Beyond our Solar System. Retrieved 2023-09-09.
- ^ Rodriguez, David R.; Zuckerman, B.; Melis, Carl; Song, Inseok (May 2011). "The Ultra Cool Brown Dwarf Companion of WD 0806-661B: Age, Mass, and Formation Mechanism". The Astrophysical Journal Letters. 732 (2): L29. arXiv:1103.3544. Bibcode:2011ApJ...732L..29R. doi:10.1088/2041-8205/732/2/L29.
- ^ Lecavelier des Etangs, A.; Lissauer, Jack J. (June 2022). "The IAU working definition of an exoplanet". New Astronomy Reviews. 94: 101641. arXiv:2203.09520. Bibcode:2022NewAR..9401641L. doi:10.1016/j.newar.2022.101641. IAU website link
- ^ "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
- ^ "WD 0806-661". NASA Exoplanet Archive. Retrieved 22 January 2024.
