1 Centauri

"i centauri" redirects here; not to be confused with j centauri, l Centauri, or ι Centauri.

1 Centauri, or i Centauri,^[10] is a yellow-white-hued binary star^[7] system in the southern constellation Centaurus. It can be seen with the naked eye, having an apparent visual magnitude of +4.23.^[2] Based upon an annual parallax shift of 51.54 mas as seen from Earth's orbit, it is located 63.3 light-years from the Sun. The system is moving closer to the Sun with a radial velocity of −21.5 km/s.^[5]

1 Centauri

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus
Right ascension	13h 45m 41.24482s[1]
Declination	−33° 02′ 37.3997″[1]
Apparent magnitude (V)	+4.23[2]
Characteristics
Spectral type	F2 V[3]
U−B color index	+0.00[4]
B−V color index	+0.38[4]
Astrometry
Radial velocity (Rv)	−21.5±0.6[5] km/s
Proper motion (μ)	RA: −462.49±0.18[1] mas/yr Dec.: −146.49±0.16[1] mas/yr
Parallax (π)	51.54±0.19 mas[1]
Distance	63.3 ± 0.2 ly (19.40 ± 0.07 pc)
Absolute magnitude (MV)	+2.81[6]
Orbit[7]
Period (P)	9.94480±0.00441 d
Eccentricity (e)	0.247±0.105
Periastron epoch (T)	2,422,737.382 ± 3.35 JD
Argument of periastron (ω) (secondary)	137.7±25.4°
Semi-amplitude (K1) (primary)	6.00±0.75 km/s
Details
Mass	1.35[6] M☉
Luminosity (bolometric)	5.857[8] L☉
Surface gravity (log g)	4.25±0.14[9] cgs
Temperature	6,898±235[9] K
Metallicity [Fe/H]	−0.09[8] dex
Rotation	2.42±0.22[8]
Rotational velocity (v sin i)	86[6] km/s
Age	1.193[9] Gyr
Other designations
i Centauri, 1 Centauri, CD−32°9603, FK5 506, GC 18593, GJ 525.1, HD 119756, HIP 67153, HR 5168, SAO 204812[10]
Database references
SIMBAD	data

Spectrographic images taken at the Cape Observatory between 1921 and 1923 showed this star has a variable radial velocity, which indicated this is a single-lined spectroscopic binary star system. The pair have an orbital period of 9.94 days and an eccentricity of about 0.2.^[7]

The primary component has received a number of different stellar classifications. For example, Jaschek et al. (1964) lists F0V, F2III, F4III and F4IV, thus ranging in evolutionary state from an ordinary F-type main-sequence star to a giant star.^[11] More recently, Houk (1982) listed a class of F3 V,^[12] matching an ordinary main-sequence star that is generating energy through hydrogen fusion at its core. The NStars project gives it a classification of F2 V.^[3]