16 Aurigae

16 Aurigae is a triple star^[12] system located 232 light years away from the Sun in the northern constellation of Auriga. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.547,^[13] and is located about 2/3 of the way from Capella toward Beta Tauri. It also lies in the midst of the Melotte 31 cluster, but is merely a line-of-sight interloper.^[6] The system has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.166 arc seconds per annum,^[14] and is moving closer to the Earth with a heliocentric radial velocity of −28 km/s.^[2]

16 Aurigae

Observation data Epoch J2000      Equinox J2000
Constellation	Auriga
Right ascension	05h 18m 10.570s[1]
Declination	+33° 22′ 17.81″[1]
Apparent magnitude (V)	4.552[2]
Characteristics
Spectral type	K2.5 IIIb CN-0.5[3]
U−B color index	+1.26[4]
B−V color index	+1.276[2]
Astrometry
Radial velocity (Rv)	−28.44[2] km/s
Proper motion (μ)	RA: +31.63±0.53[1] mas/yr Dec.: −160.73±0.25[1] mas/yr
Parallax (π)	14.04±0.58 mas[1]
Distance	232 ± 10 ly (71 ± 3 pc)
Absolute magnitude (MV)	0.28[5]
Orbit[6][7]
Period (P)	434.16±0.03 d
Semi-major axis (a)	7.24±1.59 mas
Eccentricity (e)	0.1189±0.0026
Inclination (i)	52.93±9.46°
Longitude of the node (Ω)	56.20±11.65°
Periastron epoch (T)	2,448,348.1172±17.1872 JD
Argument of periastron (ω) (secondary)	70.1±1.2°
Details
16 Aur A
Mass	1.30[2] M☉
Radius	19.86±0.89[8] R☉
Luminosity	127±11[8] L☉
Surface gravity (log g)	1.87[9] cgs
Temperature	4,264±58[2] K
Metallicity [Fe/H]	−0.40[9] dex
Rotational velocity (v sin i)	0.0[10] km/s
Age	5.07[2] Gyr
Other designations
16 Aur, NSV 1909, BD+33°1000, HD 34334, HIP 24727, HR 1726, SAO 57853, PPM 70153, ADS 3872, WDS J05182+3322[11]
Database references
SIMBAD	data

The primary component is a single-lined spectroscopic binary with an orbital period of 1.19 years and an eccentricity of 0.1189.^[6] The visible member is an aging K-type giant star with a stellar classification of K2.5 IIIb CN-0.5;^[3] sometimes just given as K3 III. The notation of the former class indicates weak lines of CN in the spectrum.^[6] This star is an estimated five^[2] billion years old with 1.30^[2] times the mass of the Sun. As a consequence of exhausting the hydrogen at its core, it has expanded to 20 times the Sun's radius. The star is radiating 127^[8] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,264 K.^[2]

A third component is an magnitude 10.6 star at an angular separation of 4.2″.^[12] It shows a common proper motion with the primary and thus is a likely third member of the system.^[6]