V762 Cassiopeiae

V762 Cassiopeiae is a red supergiant and a variable star located about 2,500 light-years away in the Cassiopeia constellation. Its apparent magnitude vary between 5.82 and 5.95, which makes it faintly visible to the naked eye under dark skies. It is a relatively cool star with an average surface temperature of 3,869 K.

V762 Cassiopeiae

The location of V762 Cassiopeiae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 01h 16m 11.902s[1]
Declination +71° 44′ 37.83″[1]
Apparent magnitude (V) 5.82 – 5.95[2]
Characteristics
Evolutionary stage Red supergiant[3]
Spectral type K5 I[3][2]
Variable type Slow irregular variable[2]
Astrometry
Radial velocity (Rv)−21.37±0.91[1] km/s
Proper motion (μ) RA: -1.658 mas/yr[1]
Dec.: 1.791 mas/yr[1]
Parallax (π)1.3148 ± 0.0693 mas[1]
Distance2,500 ± 100 ly
(760 ± 40 pc)
Details
Mass16.9±2.2[4] M☉
Radius265.7[5] R☉
Luminosity14,970[5] L☉
Temperature3869±145[3][5] K
Age10.0±1.6[4] Myr
Other designations
V762 Cas, BD+70 90, HD 7389, HIP 5926, HR 365, SAO 4358, TYC 4305-2038-1[6]
Database references
SIMBADdata

Characteristics

V762 Cassiopeiae has a spectral classification of K0 I,[3] meaning that it is an evolved K-type red supergiant star. It is estimated to be ten million years old, has around 16.9 times the Sun's mass[4] and has expanded to 266 times the Sun's diameter. It radiates 15,000 times the solar luminosity from its photosphere at an effective temperature of 3869 K,[5] which gives it an orange-red hue, typical of red supergiants.[8] Parallax measurements from the Gaia spacecraft show that V762 Cassiopeiae is located 2,480 light-years away.[1] At the estimated distance, V762 Cassiopeiae's apparent brightness is diminished by 1.04 magnitudes due to interstellar extinction.[5]

Hipparcos satellite data showed that the star is variable, and because of that it was given the variable-star designation V762 Cassiopeiae, in 1999.[9] The variability amplitude in visible light is only about 0.1 magnitudes. The International Variable Star Index lists it as an irregular variable,[2] but the General Catalogue of Variable Stars (GCVS) classifies it as a BY Draconis star.[10] The designation of GCVS is likely erroneous, since BY Draconis variability is a characteristic of main sequence stars.[11]

Distance and titleholding

Some websites claim V762 Cassiopeiae is the "farthest star visible to the naked eye", at a distance of 16,308 light-years.[12][13] This is inconsistent with parallax measurements from both Hipparcos, which found a parallax of 1.18±0.45 mas, corresponding to a distance of about 2,800 light-years,[14] and Gaia DR3, which lists a parallax of 1.3148±0.0693 mas, corresponding to a distance of about 2,500 light-years.[1][lower-alpha 1] The websites claiming that V762 Cassiopeiae is the "farthest star visible to the naked eye" also do not cite any references for the distance of 16,308 light-years, making the origin of this value uncertain.

Notes
  1. The distance (in parsecs) is equivalent to the inverse of the parallax (in arcseconds).

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. "V0762 Cas". The International Variable Star Index. AAVSO. Retrieved 8 May 2024.
  3. Messineo, M.; Brown, A. G. A. (2019-07-01). "A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2". The Astronomical Journal. 158 (1): 20. arXiv:1905.03744. Bibcode:2019AJ....158...20M. doi:10.3847/1538-3881/ab1cbd. ISSN 0004-6256. Data can be acessed here at VizieR.
  4. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011-01-01). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. ISSN 0035-8711. Data can be acessed here at VizieR.
  5. Healy, Sarah; Horiuchi, Shunsaku; Molla, Marta Colomer; Milisavljevic, Dan; Tseng, Jeff; Bergin, Faith; Weil, Kathryn; Tanaka, Masaomi (2024-03-23). "Red Supergiant Candidates for Multimessenger Monitoring of the Next Galactic Supernova". Monthly Notices of the Royal Astronomical Society. 529 (4): 3630–3650. arXiv:2307.08785. doi:10.1093/mnras/stae738. ISSN 0035-8711.
  6. "HD 7389". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 9 April 2024.
  7. EAS (1997). "The HIPPARCOS and TYCHO catalogues". Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission. ESA SP Series. 1200. Noordwijk, Netherlands: ESA Publications Division. Bibcode:1997ESASP1200.....E. ISBN 9290923997. Retrieved 15 October 2022.
  8. "The Colour of Stars". Australia National Telescope Facility. Retrieved 2024-05-27.
  9. Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (January 1999). "The 74th Special Name-list of Variable Stars" (PDF). Information Bulletin on Variable Stars. 4659: 1. Bibcode:1999IBVS.4659....1K. Retrieved 8 May 2024.
  10. "Query= V762 Cas". General Catalogue of Variable Stars. Lomonosov Moscow State University. Retrieved 8 May 2024.
  11. Chahal, Deepak; de Grijs, Richard; Kamath, Devika; Chen, Xiaodian (2022-07-06). "Statistics of BY Draconis Chromospheric Variable Stars". Monthly Notices of the Royal Astronomical Society. 514 (4): 4932–4943. arXiv:2206.05505. doi:10.1093/mnras/stac1660. ISSN 0035-8711.
  12. "Farthest Star You Can See With The Unaided Eye". Cosmoknowledge. 2021-03-26. Retrieved 2024-04-11.
  13. "How Far Back In Time Can We See With Our Naked Eye?". Big Think. 2021-05-17. Retrieved 2024-04-11.
  14. "HIP 5926". VizieR. Centre de données astronomiques de Strasbourg. Retrieved 11 April 2024.
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