Alpha1 Capricorni

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
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 Capricorni (α¹ 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.

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. It has an 8th magnitude companion, separated by 0.65 arcseconds from the primary.

In popular culture

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.