HD 156846

HD 156846
Observation data; Epoch J2000 Equinox J2000
Constellation	Ophiuchus
Right ascension	17h 20m 34.31093s
Declination	−19° 20′ 01.4944″
Apparent magnitude (V)	6.506 + 14.10
Characteristics
Spectral type	G1V + M4V
B−V color index	0.557
Astrometry
Radial velocity (Rv)	−68.50±0.22 km/s
Proper motion (μ)	RA: −137.102±0.097 mas/yr ; Dec.: −143.204±0.074 mas/yr
Parallax (π)	20.9210 ± 0.0508 mas
Distance	155.9 ± 0.4 ly ; (47.8 ± 0.1 pc)
Absolute magnitude (MV)	3.055
Details
A
Mass	1.35±0.045 M☉
Radius	2.12±0.12 R☉
Luminosity	5.07 L☉
Surface gravity (log g)	3.92±0.08 cgs
Temperature	5,969±44 K
Metallicity [Fe/H]	+0.17±0.04 dex
Rotational velocity (v sin i)	5.05±0.50 km/s
Age	2.8+0.1; −0.2 Gyr
B
Mass	0.59 M☉
Other designations
	BD−19°4605, GC 23420, HD 156846, HIP 84856, HR 6441, SAO 160474
Database references
SIMBAD	data

HD 156846 is a binary star^[5] system in the equatorial constellation of Ophiuchus, positioned a degree SSE of Messier 9.^[8] It has a yellow hue and is just barely bright enough to be visible to the naked eye with an apparent visual magnitude of 6.5.^[2] The system is located at a distance of 156 light years from the Sun based on parallax.^[1] It is drifting closer with a radial velocity of −68.5 km/s, and is predicted to come to within 85.0 light-years in about 476,000 years.^[6]

The primary, component A, is a G-type star with a stellar classification of G1V.^[4] The absolute visual magnitude of this star is 1.13 magnitudes above the main sequence, indicating it has evolved slightly off the main sequence.^[2] It has 1.35 times the mass of the Sun and 2.12 times the Sun's radius.^[2] The star is an estimated 2.8^[6] billion years old and is spinning with a projected rotational velocity of 5 km/s.^[2] It is radiating five^[6] times the luminosity of the Sun from its photosphere at an effective temperature of 5,969 K.^[2]

The magnitude 14.4 secondary companion, component B, was discovered by the American astronomer R. G. Aitken in 1910.^[3] It lies at an angular separation of 5.1″ from the primary, corresponding to a projected separation of 250 AU. This is a red dwarf with a class of M4V and has an estimated 59% of the Sun's mass.^[5]

Planetary system

On 26 October 2007, a planet HD 156846 b was found orbiting the primary star by Tamuz, using the radial velocity method.^[9] It has an orbital period of 0.98 years and a large eccentricity of 0.85. The estimated mass of this object is, at a minimum, 10.6 times the mass of Jupiter. If it were following the same orbit within the Solar System, it would have a perihelion within the orbit of Mercury and an aphelion outside the orbit of Mars.^[2]