Capella
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Capella Aa/Ab
Capella is the brightest star in Auriga
Observation data
Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation
Auriga
Component
Aa
Ab
Right ascension
05h 16m 41.3591s
Declination
+45° 59' 52.768?
Apparent magnitude (V)
0.91
0.76
0.08
(0.03 to 0.16)
Characteristics
Spectral type
G8III/K0III
G1III
U-B color index
+0.44
B-V color index
+0.80
V-R color index
-0.3
R-I color index
+0.44
Variable type
RS CVn
Astrometry
Radial velocity (Rv)
29.19 ± 0.074 km/s
Proper motion:
RA (µa cos d)
75.52 mas/yr
Dec. (µd)
-427.11 mas/yr
Parallax (p)
77.29 ± 0.89 mas
Distance
42.2 ± 0.5 ly
(12.9 ± 0.1 pc)
Absolute magnitude (MV)
0.35
0.20
-0.48
Details
Mass
2.69 ± 0.06 M?
2.56 ± 0.04 M?
Radius
12.2 ± 0.2 R?
9.2 ± 0.4 R?
Luminosity (bolometric)
78.5 ± 1.2 L?
77.6 ± 2.6 L?
Temperature
4940 ± 50 K
5700 ± 100 K
Metallicity
40% Sun
Rotation
106 ± 3 d
8.64 ± 0.09 d
Rotational velocity (v sin i)
3km/s
36km/s
Age
5.2 × 108 years
Orbit
Period (P)
104.022 ± 0.002 d
Semimajor axis (a)
56.47 ± 0.05 mas
Eccentricity (e)
0.0000 ± 0.0002
Inclination (i)
137.18 ± 0.05°
Longitude of node (O)
40.8 ± 0.1°
Periastron epoch (T)
2447528.45 ± 0.02 JD
Database references
SIMBAD
data
data
data
Other designations
Capella is the brightest star in the constellation Auriga, the sixth brightest in the night sky and the third brightest in the northern celestial hemisphere, after Arcturus and Vega. Its name is derived from the diminutive of the Latin capra "goat", hence "little goat". Capella also bears the Bayer designation Alpha Aurigae (often abbreviated to a Aurigae, a Aur or Alpha Aur). Although it appears to be a single star to the naked eye, it is actually a star system of four stars in two binary pairs. The first pair consists of two bright, large type-G giant stars, both with a radius around 10 times that of the Sun and two and a half times its mass, in close orbit around each other. Designated Capella Aa and Capella Ab, these two stars are thought to be cooling and expanding on their way to becoming red giants. The second pair, around 10,000 astronomical units from the first, consists of two faint, small and relatively cool red dwarfs. They are designated Capella H and Capella L. The stars labelled Capella C through to G and I through to K are actually unrelated stars in the same visual field. The Capella system is relatively close, at only 42.2 light-years (12.9 pc) from Earth.
^ a b c d e f g h i NAME CAPELLA – Variable of RS CVn type, database entry, SIMBAD. Accessed on line December 23, 2008.
^ a b Capella, Stars, Jim Kaler. Accessed on line December 23, 2008.
^ NSV 1897, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line December 23, 2008.
^ a b c d e f g h i j k l Very high precision orbit of Capella by long baseline interferometry, C. A. Hummel et al., The Astronomical Journal 107, #5 (May 1994), pp. 1859–1867, doi:10.1086/116995, Bibcode: 1994AJ....107.1859H. See §1 for spectral types, Table 1 for orbit, Table 5 for stellar parameters, and §6.3 for the age of the system.
^ a b c d HR 1708, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line December 23, 2008.
^ Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses, D. Pourbaix, Astronomy and Astrophysics Supplement 145 (August 2000), pp. 215–222, doi:10.1051/aas:2000237, Bibcode: 2000A&AS..145..215P; see Table 2.
^ a b On the rotation period of Capella, K. G. Strassmeier et al., Astronomische Nachrichten 322, #2 (March 2001), pp. 115–124, doi:10.1002/1521-3994(200106)322:2, Bibcode: 2001AN....322..115S.
^ a b CHANDRA-LETGS X-ray observations of Capella. Temperature, density and abundance diagnostics, R. Mewe et al., Astronomy and Astrophysics 368 (March 2001), pp. 888–900, Bibcode: 2001A&A...368..888M, doi:10.1051/0004-6361:20010026; see §1.
^ Sirius Matters, Noah Brosch, Springer: 2008, ISBN 1-4020-8318-1, p. 46.
^ Cite error: The named reference wds was invoked but never defined (see the help page).
^ Capella, in The Hundred Greatest Stars, James B. Kaler, Springer, 2002, ISBN 0-387-95436-8 (see §18); also doi:10.1007/0-387-21625-1_19.
^ Cite error: The named reference chl was invoked but never defined (see the help page).
Cite error: There are tags on this page, but the references will not show without a {{reflist|group=note}} template (see the help page).
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