Chi1 Orionis information

Chi¹ Orionis A
	; Star map of the Bayers Stars in Orion. Chi1 Orionis is indicated.
Observation data; Epoch J2000 Equinox J2000
Constellation	Orion
Right ascension	05h 54m 22.98s
Declination	+20° 16′ 34.2″
Apparent magnitude (V)	4.38 - 4.41
Characteristics
Spectral type	G0 V
U−B color index	+0.07
B−V color index	+0.59
Variable type	RS CVn
Astrometry
Radial velocity (Rv)	−15.42 km/s
Proper motion (μ)	RA: −162.54±0.28 mas/yr ; Dec.: −99.51±0.16 mas/yr
Parallax (π)	115.43 ± 0.27 mas
Distance	28.26 ± 0.07 ly ; (8.66 ± 0.02 pc)
Absolute magnitude (MV)	4.82±0.005
Orbit
Period (P)	5156.291±2.508 d
Semi-major axis (a)	89.662±0.880 Mas
Eccentricity (e)	0.452±0.002
Inclination (i)	95.937±0.790°
Longitude of the node (Ω)	126.360±0.593°
Periastron epoch (T)	2451468.2±3.083 JD
Argument of periastron (ω); (secondary)	111.527±0.230°
Semi-amplitude (K1); (primary)	1.876±0.003 km/s
Details
primary
Mass	1.01 M☉
Radius	0.979±0.009 R☉
Luminosity	1.081±0.018 L☉
Surface gravity (log g)	4.39 cgs
Temperature	5,955±6.1 K
Metallicity [Fe/H]	−0.01 dex
Rotation	5.2 days
Rotational velocity (v sin i)	8.7 km/s
Age	300–400 Myr
companion
Mass	0.15 M☉
Age	70-130 Myr
Other designations
	54 Ori, Gl 222, HR 2047, BD+20°1162, HD 39587, LTT 11743, GCTP 1354.00, SAO 77705, HIP 27913
Database references
SIMBAD	data

Chi¹ Orionis (χ¹ Ori, χ¹ Orionis) is a star about 28 light years away.^[1] It is in the constellation Orion, where it can be seen in the tip of the hunter's upraised club.^[13]

A light curve for Chi¹ Orionis, plotted from *TESS* data.^[14] The 5.5 day period derived by Stępień and Geyer is marked in red.

χ¹ Ori is a G0V star.^[8] It is listed in the General Catalog of Variable Stars as an RS Canum Venaticorum variable, varying between visual magnitude 4.38 and 4.41.^[2] Stępień and Geyer measured its period to be 5.5 days.^[15]

χ¹ Ori has a faint companion with a mass estimated at 15% of the mass of the Sun, and an orbital period of 14.1 years. The companion orbits an average distance of 6.1 AU from the primary, but has a fairly high orbital eccentricity, ranging from 3.3 AU out to 8.9 AU from the primary. Because of this red dwarf companion, the likelihood of habitable planets in this system is low. It is thought that the companion is a red dwarf still contracting towards the main sequence.^[8]

A necessary condition for the existence of a planet in this system are stable zones where the object can remain in orbit for long intervals. For hypothetical planets in a circular orbit around the individual members of this star system, this maximum orbital radius is computed to be 1.01 AU for the primary and 0.41 AU for the secondary. (Note that the orbit of the Earth is 1 AU from the Sun.) A planet orbiting outside of both stars would need to be at least 18.4 AU distant.^[16]

χ¹ Ori is a candidate stream star member of the Ursa Major Moving Group, although there is some evidence to the contrary.^[11]

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[mnras427_4_2723-16] Cite error: The named reference mnras427_4_2723 was invoked but never defined (see the help page).

Observation data Epoch J2000 Equinox J2000
Star map of the Bayers Stars in Orion. Chi¹ Orionis is indicated.
Constellation	Orion
Right ascension	05^h 54^m 22.98^s^[1]
Declination	+20° 16′ 34.2″^[1]
Apparent magnitude (V)	4.38 - 4.41^[2]
Characteristics
Spectral type	G0 V^[3]
U−B color index	+0.07^[4]
B−V color index	+0.59^[4]
Variable type	RS CVn^[2]
Astrometry

Radial velocity (R_v)	−15.42^[5] km/s
Proper motion (μ)	RA: −162.54±0.28^[1] mas/yr Dec.: −99.51±0.16^[1] mas/yr
Parallax (π)	115.43 ± 0.27 mas^[1]
Distance	28.26 ± 0.07 ly (8.66 ± 0.02 pc)
Absolute magnitude (M_V)	4.82±0.005^[6]

Orbit^[7]
Period (P)	5156.291±2.508 d
Semi-major axis (a)	89.662±0.880 Mas
Eccentricity (e)	0.452±0.002
Inclination (i)	95.937±0.790°
Longitude of the node (Ω)	126.360±0.593°
Periastron epoch (T)	2451468.2±3.083 JD
Argument of periastron (ω) (secondary)	111.527±0.230°
Semi-amplitude (K₁) (primary)	1.876±0.003 km/s
Details
primary
Mass	1.01^[8] `M`_☉
Radius	0.979±0.009^[9] `R`_☉
Luminosity	1.081±0.018^[9] `L`_☉
Surface gravity (log g)	4.39^[8] cgs
Temperature	5,955±6.1^[10] K
Metallicity [Fe/H]	−0.01^[11] dex
Rotation	5.2 days^[11]
Rotational velocity (v sin i)	8.7^[8] km/s
Age	300–400^[12] Myr
companion
Mass	0.15^[8] `M`_☉
Age	70-130^[8] Myr
Other designations
54 Ori, Gl 222, HR 2047, BD+20°1162, HD 39587, LTT 11743, GCTP 1354.00, SAO 77705, HIP 27913
Database references
SIMBAD	data

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