Alpha1 Capricorni

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For other star systems with this Bayer designation, see Alpha Capricorni.
α1 Capricorni
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Capricornus
Right ascension 20h 17m 38.9s
Declination −12° 30′ 30″
Apparent magnitude (V) +4.30/+8.5
Distance 690 ± 140 ly
(211 ± 43 pc)
Spectral type G3 Ib[1]
Other designations
Prima Giedi, Algiedi Prima, 5 Capricorni, HR 7747, HD 192876, BD−12°5683, FK5 1527, HIP 100027, SAO 163422, GC 28189, ADS 13632, CCDM J20176-1231

Alpha1 Capricorni1 Cap, α1 Capricorni) is a double star in the southern constellation of Capricornus. It also has the traditional star name Prima Giedi or Algiedi Prima, and shares the name Algedi (from الجدي - al-jadii, meaning the goat) with α² Capricorni. It is approximately 690 light years from Earth.[2]

This is a yellow G-type supergiant with an apparent magnitude of +4.30. This star has 5.3 times the mass of the Sun and is radiating around 1,047 times the Sun's luminosity.[1] It has an 8th magnitude companion, separated by 0.65 arcseconds from the primary.

In popular culture[edit]

The name Giedi Prime is used for a fictional planet in Frank Herbert's 1965 science fiction novel Dune. The planet Giedi Prime is known to be the home planet of the Harkonnens.


  1. ^ a b Smiljanic, R.; et al. (April 2006), "CNO in evolved intermediate mass stars", Astronomy and Astrophysics 449 (2): 655–671, arXiv:astro-ph/0511329, Bibcode:2006A&A...449..655S, doi:10.1051/0004-6361:20054377 
  2. ^ Kaler, Jim. "Algedi". Retrieved 27 July 2005.