Eta Cassiopeiae

Eta Cassiopeiae

η Cas in optical light
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 00h 49m 06.29070s[1]
Declination +57° 48′ 54.6758″[1]
Apparent magnitude (V) 3.44[2]/7.51[3]
Characteristics
Spectral type G0 V[4] + K7 V[3]
U−B color index +0.02[2]/1.03
B−V color index +0.58[2]/1.39
Variable type RS CVn?[5]
Astrometry
A
Radial velocity (Rv)+10.0 ± 0.1[6] km/s
Proper motion (μ) RA: 1,086.59[1] mas/yr
Dec.: –559.43[1] mas/yr
Parallax (π)168.8322 ± 0.1663 mas[7]
Distance19.32 ± 0.02 ly
(5.923 ± 0.006 pc)
Absolute magnitude (MV)4.57[8]
B
Proper motion (μ) RA: 1144.693[9] mas/yr
Dec.: –469.668[9] mas/yr
Parallax (π)168.7186 ± 0.0216 mas[9]
Distance19.331 ± 0.002 ly
(5.9270 ± 0.0008 pc)
Orbit[10]
CompanionEta Cassiopeiae B
Period (P)480 yr
Semi-major axis (a)11.9939″
Eccentricity (e)0.497
Inclination (i)34.76°
Longitude of the node (Ω)98.42°
Periastron epoch (T)1889.6
Argument of periastron (ω)
(secondary)		88.59°
Details
η Cas A
Mass0.95±0.08[3] M☉
Radius1.00[11] R☉
Luminosity1.2321±0.0074[12] L☉
Surface gravity (log g)4.4±0.3[11] cgs
Temperature6,010[11] K
Metallicity [Fe/H]–0.31[3] dex
Rotational velocity (v sin i)3.15[4] km/s
Age5.4 ± 0.9[13] Gyr
η Cas B
Mass0.57±0.07[3] M☉
Radius0.66[14] R☉
Luminosity0.0646+0.0131
−0.0109[3] L☉
Temperature4,036±150[3] K
Other designations
Achird, η Cas 24 Cassiopeiae, ADS 671, BD+57°150, GCTP 155, GJ 34, HD 4614, HIP 3821, HR 219, LHS 123/122, LFT 74, LTT 10287, SAO 21732, Wolf 24, Struve 60, GC 962, CCDM J00491+5749[6]
Database references
SIMBADThe system
A
B
η Cassiopeiae is located in the constellation Cassiopeia
η Cassiopeiae is located in the constellation Cassiopeia
Location of η Cassiopeiae in the constellation Cassiopeia

Eta Cassiopeiae (η Cassiopeiae, abbreviated Eta Cas, η Cas) is a binary star system in the northern constellation of Cassiopeia. Its binary nature was first discovered by William Herschel in August 1779. Based upon parallax measurements, the distance to this system is 19.42 light-years (5.95 parsecs) from the Sun.[1] The two components are designated Eta Cassiopeiae A (officially named Achird /ˈeɪtʃərd/)[15] and B.

  1. ^ a b c d e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference clpl4_99 was invoked but never defined (see the help page).
  3. ^ a b c d e f g Cite error: The named reference aaa338 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference aaa520_A79 was invoked but never defined (see the help page).
  5. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  6. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  7. ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  8. ^ Cite error: The named reference Holmberg2009 was invoked but never defined (see the help page).
  9. ^ a b c Cite error: The named reference edr3b was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference aj74 was invoked but never defined (see the help page).
  11. ^ a b c Cite error: The named reference gray2019 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Boyajian2013 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference apj746_1_101 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference apjss53 was invoked but never defined (see the help page).
  15. ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.