HD 149382

HD 149382 is a hot subdwarf star in the constellation of Ophiuchus with an apparent visual magnitude of 8.943.^[2] This is too faint to be seen with the naked eye even under ideal conditions, although it can be viewed with a small telescope.^[8] Based upon parallax measurements, this star is located at a distance of about 246 light-years (75.5 parsecs) from the Earth.

HD 149382

Observation data Epoch J2000      Equinox J2000
Constellation	Ophiuchus
Right ascension	16h 34m 23.33337s[1]
Declination	−04° 00′ 52.0301″[1]
Apparent magnitude (V)	8.943[2]
Characteristics
Spectral type	B5 VI[3]
U−B color index	−1.143[2]
B−V color index	−0.282[2]
V−R color index	−0.127[2]
R−I color index	−0.135[2]
Astrometry
Radial velocity (Rv)	+3[4] km/s
Proper motion (μ)	RA: −6.234[1] mas/yr Dec.: −5.780[1] mas/yr
Parallax (π)	13.2407±0.0567 mas[1]
Distance	246 ± 1 ly (75.5 ± 0.3 pc)
Details
Mass	0.29 – 0.53[5] M☉
Radius	0.143[6] R☉
Luminosity	25.2[6] L☉
Surface gravity (log g)	5.80±0.05[5] cgs
Temperature	35,500±500[5] K
Metallicity [Fe/H]	−1.30[3] dex
Rotational velocity (v sin i)	4.9±1.4[5] km/s
Other designations
BD−03°3967, HD 149382, HIP 81145, SAO 141250[7]
Database references
SIMBAD	data

This is the brightest known B-type subdwarf star with a stellar classification of B5 VI. It is generating energy through the thermonuclear fusion of helium at its core (triple-alpha process).^[3] The effective temperature of the star's outer envelope is about 35,500 K, giving it the characteristic blue-white hue of a B-type star. Although only about one seventh the diameter of the Sun, it radiates about 25 times as much due to its high temperature. HD 149382 has a visual companion located at an angular separation of 1 arcsecond.^[9]

In 2009, a substellar companion, perhaps even a superjovian planet, was announced orbiting the star. This candidate object was estimated to have 8 to 23 times the mass of Jupiter.^[5] In 2011, this discovery was thrown into doubt when an independent team of astronomers were unable to confirm the detection. Their observations rule out a companion with a mass greater than Jupiter orbiting with a period of less than 28 days.^[9]

See also

• List of brown dwarfs