Delta Capricorni
Delta Capricorni, or δ Capricorni, is a binary star located 38.7 light-years from the Sun in the constellation of Capricornus (the Sea Goat). The system consists of an eclipsing binary, Delta Capricorni A, and two visual companions that are over 10 magnitudes fainter, labeled B and C. Delta Capricorni A's two components are designated Delta Capricorni Aa (formally named Deneb Algedi /ˌdɛnɛb ælˈdʒiːdiː/, the traditional name of the system) and Ab. The primary star, Aa, is a white giant and the combined light of Aa and Ab makes it the brightest star in the constellation.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21h 47m 02.44424s |
| Declination | −16° 07′ 38.2335″ |
| Apparent magnitude (V) | 2.81 (2.81 (- 2.90) - 3.05) |
| Characteristics | |
| Spectral type | A7m III (kA5hF0mF2III) |
| U−B color index | +0.07 |
| B−V color index | +0.31 |
| Variable type | Eclipsing binary (Algol-type) |
| Astrometry | |
| Radial velocity (Rv) | −6.3 km/s |
| Proper motion (μ) | RA: +261.70 mas/yr Dec.: −296.70 mas/yr |
| Parallax (π) | 84.27 ± 0.19 mas |
| Distance | 38.70 ± 0.09 ly (11.87 ± 0.03 pc) |
| Absolute magnitude (MV) | +2.48 |
| Orbit | |
| Primary | δ Cap Aa |
| Companion | δ Cap Ab |
| Period (P) | 1.0227683 days |
| Eccentricity (e) | 0 (assumed) |
| Inclination (i) | 72.5° |
| Periastron epoch (T) | 2,448,105.793 ± 0.003 HJD |
| Semi-amplitude (K1) (primary) | 75.3 ± 1.0 km/s |
| Details | |
| δ Cap Aa | |
| Mass | 2.0 M☉ |
| Radius | 1.91 R☉ |
| Luminosity | 8.5 L☉ |
| Surface gravity (log g) | 3.66 cgs |
| Temperature | 7,301 K |
| Metallicity [Fe/H] | –0.13 dex |
| Rotational velocity (v sin i) | 105 km/s |
| δ Cap Ab | |
| Mass | 0.73 M☉ |
| Radius | 0.9 R☉ |
| Temperature | 4,500 K |
| Other designations | |
Deneb Algedi, Deneb Algiedi, Scheddi, δ Cap, Del Cap, 49 Capricorni, BD−16 5943, FK5 819, GJ 837, HD 207098, HIP 107556, HR 8322, SAO 164644, ADS 15314, WDS 21470-1608 | |
| Database references | |
| SIMBAD | data |
Delta Capricorni is 2.6 degrees south of the ecliptic and can be occulted by the Moon, and (rarely) by planets.
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