V762 Cassiopeiae Explained

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 3,869K.

Characteristics

V762 Cassiopeiae has a spectral classification of K0I, 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 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 3869K, which gives it an orange-red hue, typical of red supergiants.[1] Parallax measurements from the Gaia spacecraft show that V762 Cassiopeiae is located 2,480 light-years away. At the estimated distance, V762 Cassiopeiae's apparent brightness is diminished by 1.04 magnitudes due to interstellar extinction.

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

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.[3] [4] This is inconsistent with parallax measurements from both Hipparcos, which found a parallax of, corresponding to a distance of about 2,800 light-years, and Gaia DR3, which lists a parallax of, corresponding to a distance of about 2,500 light-years. The websites claiming that V762 Cassiopeiae is the "farthest star visible to the naked eye" also do not cite any references for the distance of 16,308 light-years, making the origin of this value uncertain.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 and References

  1. Web site: The Colour of Stars . Australia National Telescope Facility . 6 March 2024 . 2024-05-27 .
  2. 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 . 10.1093/mnras/stac1660 . free . 0035-8711. 2206.05505 .
  3. Web site: 2021-03-26 . Farthest Star You Can See With The Unaided Eye . 2024-04-11 . Cosmoknowledge . en-US.
  4. Web site: 2021-05-17 . How Far Back In Time Can We See With Our Naked Eye? . 2024-04-11 . Big Think . en-US.