HD 38858

HD 38858 is a star in the Orion constellation. It is a G-type main-sequence star, located at a distance of about 50 light-years. It has an apparent magnitude of 5.97, therefore can be seen to the naked eye only in sufficiently dark skies.

HD 38858

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Orion[1]
Right ascension	05h 48m 34.94026s[2]
Declination	−04° 05′ 40.7218″[2]
Apparent magnitude (V)	+5.97[3]
Characteristics
Evolutionary stage	main sequence[2]
Spectral type	G4V[4]
U−B color index	+0.10[3]
B−V color index	+0.64[3]
Astrometry
Radial velocity (Rv)	+31.2[5] km/s
Proper motion (μ)	RA: +61.427[2] mas/yr Dec.: −229.291[2] mas/yr
Parallax (π)	65.7446±0.0307 mas[2]
Distance	49.61 ± 0.02 ly (15.210 ± 0.007 pc)
Absolute magnitude (MV)	+5.06[6]
Details
Mass	0.886[7] M☉
Radius	0.9331±0.0162[7] R☉
Luminosity	0.7943±0.0101[7] L☉
Surface gravity (log g)	4.36±0.06[4] cgs
Temperature	5,660±20[4] K
Metallicity [Fe/H]	−0.27±0.03[4] dex
Rotational velocity (v sin i)	2.61[8] km/s
Age	6.2[9] Gyr
Other designations
BD−04°1244, FK5 1155, GJ 1085, HD 38858, HIP 27435, LTT 2380, SAO 132554
Database references
SIMBAD	data
Exoplanet Archive	data

The last observation of this system for a dust disc or comet belt was in 2009 by the Spitzer Space Telescope; a belt was inferred at 102 AU.^[9] It has an inclination of 48◦.^[10]

The star exhibit a magnetic activity cycle remarkably similar to that of Sun, with the period of 10.8 years.^[11]

Planetary system

Debris disk with the REASONS survey^[12]

The exoplanet HD 38858 b was discovered in 2011 in orbit in its host star's habitable zone, a zone in which Earth-like conditions (namely the presence of liquid water) on a planet's surface are possible.^[13][14] The planet is likely a gas giant, a type of planet which astronomers believe is unlikely to support life as it is currently understood. However, the planet could have a rocky natural satellite capable of sustaining an Earth-like environment.^[15]

The existence of this planet was disputed since 2015 though, attributing the planetary signal to the frequency-domain alias of the star magnetic activity cycle, although the existence of another planet on the 198-day orbit is suspected.^[11]

The HD 38858 planetary system^[16]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b (disputed[11])	32[17] M🜨	1.0376±0.0189	407.15±4.2857	0.27±0.17	—	—
Disk	102 AU				—	—