Eta Cassiopeiae

Starbox begin
name=Eta Cassiopeiae A/B Starbox observe
epoch=J2000
constell=Cassiopeia
ra=RA|00|49|06.2912cite web
url=http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=V*+eta+Cas
title=SIMBAD query result: V* eta Cas -- Spectroscopic binary
publisher=Centre de Données astronomiques de Strasbourg
accessdate=2008-04-10 ]
dec=DEC|+57|48|54.674
appmag_v=3.45/7.51cite journal
last=Fernandes | first=J.
coauthors=Lebreton, Y., Baglin, A., Morel, P.
title=Fundamental stellar parameters for nearby visual binary stars: eta Cas, XI Boo, 70 OPH and 85 Peg
journal=Astronomy and Astrophysics
year=1998 | volume=338 | pages=455–464
url=http://adsabs.harvard.edu/abs/1998A&A...338..455F
accessdate=2008-04-10 ] Starbox character
class=G0V/K7V
b-v=0.57/1.39
u-b=0.02/1.03
variable=RS CVn Starbox astrometry
radial_v=+10.0±0.1
prop_mo_ra=1087.07
prop_mo_dec=−559.73
parallax=167.99
p_error=0.62
parallax_footnote=
absmag_v=4.59/8.64 Starbox visbin
reference= [cite journal
last=Strand | first=K. A.
title=The orbit of Eta Cassiopeiae
journal=Astronomical Journal
year=1969 | volume=74 | pages=760–763
url=http://adsabs.harvard.edu/abs/1969AJ.....74..760S
accessdate=2008-04-10
doi=10.1086/110853 ]
name=η Cas B
period=480
axis=11.9939
eccentricity=0.497
inclination=34.76
node=98.42
periarg=88.59
periastron=1889.6 Starbox detail
age=
metal= [Fe/H] = −0.031
mass=0.95/0.62
radius=1.01/0.66 [cite journal
last=Johnson | first=H. M. | coauthors=Wright, C. D.
title=Predicted infrared brightness of stars within 25 parsecs of the sun
journal=Astrophysical Journal Supplement Series
year=1983 | volume=53 | pages=643–711
url=http://adsabs.harvard.edu/abs/1983ApJS...53..643J
accessdate=2008-04-16
doi=10.1086/190905 —see p. 647.]
rotation=6 km/s
luminosity=1.29/0.06
temperature=6,087/4,036 Starbox catalog
names=Achird, η Cas 24 Cassiopeiae, GJ 34, HR 219, BD+57°150, HD 4614, GCTP 155, LHS 123/122, LFT 74, LTT 10287, SAO 21732, Wolf 24, Struve 60, HIP 3821, GC 962, ADS 671, CCDM J00491+5749

Eta Cassiopeiae (η Cas / η Cassiopeiae) is a star system 19.4 light years away from Earth, in the constellation Cassiopeia. Sometimes the traditional name Achird is used. It is known as 王良三 (the Third Star of Wang Liang) in Chinese.Fact|date=May 2008

The primary star in the η Cassiopeiae system is a yellow dwarf (main sequence) star of spectral type G0V, putting it in the same spectral class as our Sun, which is of spectral type G2V. It therefore resembles what our Sun might look like if we were to observe it from η Cassiopeiae. The star is of apparent magnitude 3.45. The star has a cooler and dimmer (magnitude 7.51) orange dwarf companion of spectral type K7V. The system is an RS Canum Venaticorum type variable star and its brightness varies by 0.05 magnitudes.

Based on an estimated semimajor axis of 12″ and a parallax of 0.168″, the two stars are separated by an average distance of 71 AU, where an AU is the average distance between the Sun and the Earth. [cite book
first=Albrecht | last=Unsöld | coauthors=Baschek, Bodo
title=The New Cosmos: An Introduction to Astronomy and Astrophysics
year=2001 | pages=p. 186
publisher=Springer | edition=5th edition
isbn=3540421777 ] However, the large orbital eccentricity of 0.497 means that their periapsis, or closest approach, is as small as 36 AU. For comparison, the semi-major axis of Neptune is 30 AU. There are six dimmer optical components listed in the Washington Double Star Catalog. However, none of them are related to the η Cassiopeiae system and are in reality more distant stars.

See also

* Eta Cassiopeiae in fiction

References

External links

* cite web
title=Eta Cassiopeiae 2 | work=SolStation
url=http://www.solstation.com/stars/eta-cass.htm
accessdate=2005-11-03
*cite web
last=Kaler | first=Jim | title=Achird
url=http://www.astro.uiuc.edu/~kaler/sow/achird.html
publisher=University of Illinois at Urbana-Champaign
accessdate=2008-04-10