Rho Cassiopeiae

Rho Cassiopeiae

Location of Rho Cassiopeiae in the Cassiopeia constellation.
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 23h 54m 23.0s[1]
Declination +57° 29′ 58″[1]
Apparent magnitude (V) 4.1 to 6.2[2]
Characteristics
Spectral type G2Iae[3] (F8pIa-K0pIa-0)[2]
U−B color index 1.15[4]
B−V color index 1.26[4]
Variable type SRd[2]
Astrometry
Radial velocity (Rv)−47[3] km/s
Proper motion (μ) RA: −4.54[1] mas/yr
Dec.: −3.45[1] mas/yr
Parallax (π)0.9470 ± 0.2021 mas[5]
Distance8,150±1,630 ly
(2,500±500 pc)[6]
Absolute magnitude (MV)–9.5[7]
Details
Mass40[7] M☉
Radius564±67 – 700±112[8] R☉
Luminosity302,000 – 530,000,[6] 129,000[9] L☉
Surface gravity (log g)0.1[3] cgs
Temperature4,571 – 6,044[6] K
Metallicity [Fe/H]0.3[10] dex
Rotational velocity (v sin i)25[11] km/s
Age4 – 6[7] Myr
Other designations
7 Cassiopeiae, HR 9045, BD+56°3111, HD 224014, SAO 35879, FK5 899, HIP 117863, GC 33160
Database references
SIMBADdata

Rho Cassiopeiae (/ˌroʊ kæsiəˈpiːaɪ, -sioʊ-, -iː/; ρ Cas, ρ Cassiopeiae) is a yellow hypergiant star in the constellation Cassiopeia. It is about 8,150 light-years (2,500 pc) from Earth, yet can still be seen by the naked eye as it is over 300,000 times brighter than the Sun. On average it has an absolute magnitude of −9.5, making it visually one of the most luminous stars known. Recently imaged and measured by the CHARA array in 2024, its diameter measures between 564 and 700 times that of the Sun, approximately 879,000,000 kilometers (5.88 AU; 546,000,000 mi), or 2.6 to 3.3 times the size of Earth's orbit.[8]

Rho Cassiopeiae is a single star, and is categorized as a semiregular variable. As a yellow hypergiant, it is one of the rarest types of stars. Only a few dozen are known in the Milky Way, but it is not the only one in its constellation which also contains V509 Cassiopeiae.[12]

  1. ^ a b c d Cite error: The named reference hipparcos was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference GCVS-Rho-Cas was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference klotchkova was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference ducati was invoked but never defined (see the help page).
  5. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  6. ^ a b c van Genderen, A. M.; Lobel, A.; Nieuwenhuijzen, H.; Henry, G. W.; De Jager, C.; Blown, E.; Di Scala, G.; Van Ballegoij, E. J. (2019). "Pulsations, eruptions, and evolution of four yellow hypergiants". Astronomy and Astrophysics. 631: A48. arXiv:1910.02460. Bibcode:2019A&A...631A..48V. doi:10.1051/0004-6361/201834358. S2CID 203836020.
  7. ^ a b c Cite error: The named reference gorlova was invoked but never defined (see the help page).
  8. ^ a b Anugu, Narsireddy; Baron, Fabien; Monnier, John D.; Gies, Douglas R.; Roettenbacher, Rachael M.; Schaefer, Gail H.; Montargès, Miguel; Kraus, Stefan; Bouquin, Jean-Baptiste Le (2024-08-05). "CHARA Near-Infrared Imaging of the Yellow Hypergiant Star $\rho$ Cassiopeiae: Convection Cells and Circumstellar Envelope". arXiv:2408.02756v2 [astro-ph.SR].
  9. ^ Klochkova, V. G. (2019). "Unity and Diversity of Yellow Hypergiants Family". Astrophysical Bulletin. 74 (4): 475–489. arXiv:1911.09387. Bibcode:2019AstBu..74..475K. doi:10.1134/S1990341319040138. S2CID 208202411.
  10. ^ Cite error: The named reference israelian was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference lobel was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference border was invoked but never defined (see the help page).