Alpha2 Capricorni

Alpha2 Capricorni
α¹ and α² are combined in this chart, to be held upwards, so west is right of page. Nu Capricorni to the east is not to be confused, nor 3 Capricorni even closer in angular distance to the west.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Capricornus
Right ascension 20h 18m 03.25595s[1]
Declination −12° 32′ 41.4684″[1]
Apparent magnitude (V) +3.57[2]
Characteristics
Spectral type G8.5III-IV[3]
U−B color index +0.69[2]
B−V color index +0.94[2]
Astrometry
Radial velocity (Rv)−0.47±0.47[4] km/s
Proper motion (μ) RA: +62.63[1] mas/yr
Dec.: +2.66[1] mas/yr
Parallax (π)31.9795 ± 0.3485 mas[5]
Distance102 ± 1 ly
(31.3 ± 0.3 pc)
Absolute magnitude (MV)+0.98+0.07
−0.06[6]
Details[7]
α2 Cap A
Mass2.05±0.29 M☉
Radius8.38±0.58 R☉
Luminosity40.4±2.2 L☉
Surface gravity (log g)3.0[4] cgs
Temperature5,030±160 K
Metallicity [Fe/H]−0.15±0.10 dex
Rotational velocity (v sin i)2.7[4] km/s
Age1.30±1.04 Gyr
Other designations
Gredi, Algedi, Secunda Giedi, Algiedi Secunda, α2 Cap, 6 Cap, ADS 13645, BD−12° 5685, FK5 761, HD 192947, HIP 100064, HR 7754, SAO 163427, WDS J20181-1233A,BC[8]
Database references
SIMBADdata

Alpha2 Capricorni (α2 Capricorni), or Algedi /ælˈdʒiːdi/,[9][10] is a triple star system[11] in the southern constellation of Capricornus. It is visible to the naked eye with an apparent visual magnitude of +3.57.[2] It is separated from the fainter α¹ Capricorni by 0.11° of the sky, a gap just resolvable with the naked eye, similar to Mizar and Alcor. Based on parallax shift as refined from orbits around the Sun of the Gaia spacecraft at Earth's Lagrange point 2, the star is 101 to 103 light years from the Solar System.

  1. ^ a b c d Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Nicolet1978 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference Gray2006 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Massarotti2008 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. ^ Cite error: The named reference Carney2008 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Reffert2015 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  10. ^ Cite error: The named reference IAU-CSN was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).