42 Capricorni
Binary star system in the constellation Capricornus / From Wikipedia, the free encyclopedia
42 Capricorni is a binary star[11] system in the zodiac constellation of Capricornus. It has a combined apparent visual magnitude of 5.18,[3] so it is faintly visible to the naked eye. Its annual parallax shift of 30.09 mas yields a distance estimate of about 108 light years; the system is moving closer to the Sun with a radial velocity of −1.2 km/s.[6] 42 Capricorni is 0.2 degree south of the ecliptic and so is subject to lunar occultations.[12]
Observation data Epoch J2000 Equinox | |
---|---|
Constellation | Capricornus |
Right ascension | 21h 41m 32.85882s[2] |
Declination | −14° 02′ 51.3964″[2] |
Apparent magnitude (V) | 5.18[3] |
Characteristics | |
Spectral type | G1 IV[4] (G1 IV + G2 V)[5] |
U−B color index | +0.20[3] |
B−V color index | +0.65[3] |
Variable type | RS CVn[5] |
Astrometry | |
Radial velocity (Rv) | −1.20±0.05[6] km/s |
Proper motion (μ) | RA: −123.05[2] mas/yr Dec.: −308.50[2] mas/yr |
Parallax (π) | 30.09 ± 0.32 mas[2] |
Distance | 108 ± 1 ly (33.2 ± 0.4 pc) |
Absolute magnitude (MV) | +2.73[7] (2.79 + 4.73)[5] |
Orbit[8] | |
Period (P) | 13.174 d |
Eccentricity (e) | 0.1763±0.0025 |
Periastron epoch (T) | 2447863.626 ± 0.027 JD |
Argument of periastron (ω) (secondary) | 166.45±0.83° |
Semi-amplitude (K1) (primary) | 25.57±0.06 km/s |
Semi-amplitude (K2) (secondary) | 35.16±0.25 km/s |
Details | |
42 Cap A | |
Mass | 1.09[9] M☉ |
Radius | 2.6[5] R☉ |
Surface gravity (log g) | 3.76[4] cgs |
Temperature | 5,634[4] K |
Metallicity [Fe/H] | −0.10[4] dex |
Rotational velocity (v sin i) | 5.2[5] km/s |
Age | 6.7[9] Gyr |
42 Cap B | |
Rotational velocity (v sin i) | 4.4[5] km/s |
Other designations | |
Database references | |
SIMBAD | data |
This is a double-lined close spectroscopic binary with an orbital period of 13.174 days and an eccentricity of 0.18.[8] The binary nature of this system was discovered in 1918 by the English astronomer Joseph Lunt. It has a combined spectrum that matches a stellar classification of G1 IV,[4] with the individual components having estimated classes of G1 V and G2 V. This is an RS Canum Venaticorum variable, indicating the presence of an active chromosphere with star spots.[5] The system is a source of X-ray emission.[13]