V762 Cassiopeiae

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V762 Cassiopeiae
V762 Cassiopeiae.png
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]
Distance 2,500 ± 100  ly
(760 ± 40  pc)
Details
Mass 16.9±2.2 [4]   M
Radius 265.7 [5]   R
Luminosity 14,970 [5]   L
Temperature 3869±145 [3] [5]   K
Age 10.0±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
SIMBAD data

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.

Contents

Characteristics

A light curve for V762 Cassiopeiae, plotted from Hipparcos data V762CasLightCurve.png
A light curve for V762 Cassiopeiae, plotted from Hipparcos data

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).

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References

  1. 1 2 3 4 5 6 7 8 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. 1 2 3 4 "V0762 Cas". The International Variable Star Index. AAVSO. Retrieved 8 May 2024.
  3. 1 2 3 4 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. V762 Cassiopeiae's database entry at VizieR.
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  5. 1 2 3 4 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.
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  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.
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