Alpha ² Capricorni

Database links to α ² Capricorni

Double star α 2 Capricorni
α 2 cap in the constellation "Capricorn"
AladinLite
Observation dates equinox :  J2000.0 , epoch : J2000.0
Constellation	Capricorn
Right ascension	20 h 18 m 3.26 s
declination	-12 ° 32 ′ 41.5 ″
Apparent brightness	3.74 likes
Typing
B − V color index	0.93
U − B color index	0.69
R − I index	0.49
Spectral class	G8.5 III-IV
Astrometry
Radial velocity	−25.79 ± 0.15 km / s
parallax	(30.82 ± 0.19)  mas
distance	(105.8 ± 0.7)  ly (32.4 ± 0.2)  pc
Proper movement
Rec. Share:	(62.63 ± 0.20)  mas / a
Dec. portion:	(2.66 ± 0.15)  mas / a
Physical Properties
Other names and catalog entries
Bayer name α 2 capricorni Flamsteed name 6 capricorni Bonn survey BD −12 ° 5685 Bright Star Catalog HR 7754 [1] Henry Draper Catalog HD 192947 [2] Hipparcos catalog HIP 100064 [3] SAO catalog SAO 163427 [4] Tycho catalog TYC 5749-2530-1 [5] 2MASS catalog 2MASS 20180324-1232418 [6] Other names WDS 20181-1233 CCDM 20181-1233

Alpha ² Capricorni (α ² Cap) is a telescopic multiple star in the constellation Capricorn . It has a total brightness of 3.7 mag and its distance is approximately 106 light years .

Alpha ² Capricorni is a system made up of four components. The main star A is a yellow giant star (or sub-giant) with about 34 times the luminosity of the sun . In 1827, John Herschel found about 8 arc seconds next to the bright star A an almost 1000 times weaker companion BC with an apparent magnitude of 11.1 mag. This star could again be recognized as double by Alvan Graham Clark in 1874 , its two components B and C with almost the same brightness of 11.2 and 11.5 mag are only slightly more than 1 "apart. Clark had already described another component D in 1838. This star has a magnitude of 10.5 mag and at the time of its discovery was about 200 ″ from the main star A, today the distance is still about 150 ″.

Alpha ² was together with the star Alpha ¹ Capricorni also with the proper name " Algiedi " or "Algedi" (from Arabic الجدي, DMG al-ǧady  'the billy goat'). To distinguish it from this, it was also called "Secunda Giedi". According to the “IAU Catalog of Star Names” of the Working Group on Star Names (WGSN) of the IAU for the standardization of star names, the name in the form “Algedi” was only assigned to the lighter Alpha ² Capricorni in 2016 .

Individual evidence

1. ↑ ^{a b c d e} VizieR: Hipparcos, the New Reduction (van Leeuwen, 2007) - The Astrometric Catalog
2. ↑ ^{a b} VizieR: Stellar Photometry in Johnson's 11-color system (Ducati, 2002)
3. ^ VizieR: Southern B and Be stars (Levenhagen +, 2006)
4. ↑ VizieR: General Catalog of Stellar Radial Velocities (Wilson, 1953)
5. ↑ VizieR: The Washington Visual Double Star Catalog (Mason + 2001-2014)
6. ↑ Bulletin of the IAU Working Group on Star Names, No. 2. IAU Division C Education, Outreach and Heritage, 2016 ( PDF; 158 KB ).