NML Cygni
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 46m 25.6s |
| Declination | +40° 06′ 59.4″ |
| Apparent magnitude (V) | 16.60 |
| Characteristics | |
| Spectral type | M6I[1] |
| B−V color index | 2.0 |
| Variable type | Semiregular |
| Astrometry | |
| Proper motion (μ) | RA: -1.55[2] mas/yr Dec.: -4.59[2] mas/yr |
| Parallax (π) | 0.620[2] ± 0.047[2] mas |
| Distance | 1.61k[2] pc |
| Details | |
| Mass | 25–40[2] M☉ |
| Radius | 1,650[2] R☉ |
| Luminosity | 270,000[2] L☉ |
| Other designations | |
V* V1489 Cyg, RAFGL 2650, IRC +40448 | |
| Database references | |
| SIMBAD | data |
NML Cygni or V1489 Cygni is a red hypergiant star[2] and one of the largest stars currently known, at about 1,650 times the Sun's radius (equal to 7.67 astronomical units), thus a diameter of about 2,295,000,000 kilometres (1.426×109 mi). If placed at the center of the Solar System, NML Cygni's surface would extend beyond the orbit of Jupiter, filling over half the gap between Jupiter and Saturn's orbit. It contains the volume of approximately 3.6 billion times that of the Sun.
It is one of the extreme luminous hypergiant stars.[3] Its distance from Earth is estimated to be around 1.6 kpc, or about 5,300 light-years.[3]
NML Cygni is a part of the Cygnus OB2 association. The Cyg OB2 association spans nearly 2° on the sky, or ∼30 pc in radius at the distance of 1.74 ± 0.2 kpc, thus it is one of the closest massive associations to the Sun.[4] It has an estimated mass loss rate of 2×10−4M⊙yr−1.[5] The annual parallax of this star is measured to be around 0.62 milli-arc-seconds.[2]
Characteristics
This star has a dusty environment surrounding it,[2][4] and it exhibits a bean-shaped asymmetric nebula that is coincident with the distribution of its H2O vapor masers.[6] It is a semiregular variable star with a period of around 940 days.[4]
The bolometric luminosity (Lbol) for this star is near 3 × 105 L☉. Its bolometric magnitude (Mbol) is around −9.0. It is one of the most luminous cool hypergiant stars.[4]
From the observations, it is estimated that this star has two discrete optically thick envelopes of dust and molecules. The optical depth of the inner shell is found to be 1.9, while that of the outer one is 0.33.[7] NML Cygni has one of the largest mass-loss rates at around 2 × 10-4 M☉ per year.[8] These dust envelopes are formed due to the strong post-mainsequence wind velocity and the high mass emission rate. The post-MS wind velocity is 23 km/s. Because of its unique location within the Milky Way, NML Cygni does not dominate its local interstellar environment.[4]
Observational history
NML Cygni was discovered in 1965, by Neugebauer, Martz, and Leighton.[8] The name NML comes from the names of these three discoverers.[9] It has also been given the designation V1489 on account of the small semi-regular brightness variations caused by pulsations and mass loss.
NML Cygni is a massive oxygen-rich star.[5] Its composition began to be revealed with the discovery of OH masers (1612 MHz) in 1968 (Wilson and Barrett). The presence of molecules like H2O, SiO, CO, HCN, CS, SO, SO2, and H2S was also revealed in the later years.[8]
See also
References
- ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1086/382218, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1086/382218instead. - ^ a b c d e f g h i j k Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1051/0004-6361/201219587, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1051/0004-6361/201219587instead. - ^ a b Michael Thomas Schuster (2007). Investigating the Circumstellar Environments of the Cool Hypergiants. ProQuest. p. 57. ISBN 978-0-549-32782-0. Retrieved 27 August 2012.
- ^ a b c d e Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1088/0004-637X/699/2/1423, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1088/0004-637X/699/2/1423instead. - ^ a b "Combined Array for Research in Millimeter-wave Astronomy" (PDF). Retrieved August 27, 2012.
- ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1086/498395, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1086/498395instead. - ^ W. C. DanchiI, W. H. Green, D. D. S. Hale, K. McEleroy, J. D. Monnier, P. G. Tuthill, C. H. Townes (2001). "Proper Motions of Dust Shells Surrounding NML Cygni". The Astrophysical Journal.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ a b c Kevin Marvel (19 December 1996). "NML Cygni". The Circumstellar Environment of Evolved Stars As Revealed by Studies of Circumstellar Water Masers. Universal-Publishers. pp. 182–212. ISBN 978-1-58112-061-5. Retrieved 23 August 2012.
- ^ J. B. Hearnshaw (2 May 1996). "New infrared sources and their interpretation". The Measurement of Starlight: Two Centuries of Astronomical Photometry. Cambridge University Press. p. 278. ISBN 978-0-521-40393-1. Retrieved 23 August 2012.