30 Vulpeculae

30 Vulpeculae is a binary star system in the northern constellation of Vulpecula, located mid-way between Epsilon Cygni and a diamond-shaped asterism in Delphinus. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.91.[2] The system is located approximately 350 light years away from the Sun based on parallax,[1] and is drifting further away with a mean radial velocity of +30 km/s.[4] The system has a relatively high proper motion, traversing the celestial sphere at the rate of 0.186 arc seconds per annum.[11]

30 Vulpeculae

Location of 30 Vulpeculae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Vulpecula
Right ascension	20h 44m 52.50423s[1]
Declination	25° 16′ 14.2538″[1]
Apparent magnitude (V)	4.91[2]
Characteristics
Spectral type	K1 III[3]
U−B color index	+1.18[2]
B−V color index	+1.19[2]
Astrometry
Radial velocity (Rv)	+30.00[4] km/s
Proper motion (μ)	RA: −30.988[1] mas/yr Dec.: −184.648[1] mas/yr
Parallax (π)	9.3255 ± 0.1537 mas[1]
Distance	350 ± 6 ly (107 ± 2 pc)
Absolute magnitude (MV)	−0.07[5]
Orbit[6]
Period (P)	2,506±4 d
Eccentricity (e)	0.383±0.023
Periastron epoch (T)	42511±29 MJD
Argument of periastron (ω) (secondary)	272±5°
Semi-amplitude (K1) (primary)	4.69±0.13 km/s
Details
Mass	1.55[7] M☉
Radius	21.68+0.47 −0.63[1] R☉
Luminosity	173.3±3.3[1] L☉
Surface gravity (log g)	2.47[8] cgs
Temperature	4,498+67 −48[1] K
Metallicity [Fe/H]	−0.10[5] dex
Rotational velocity (v sin i)	1.5[9] km/s
Age	4.20[7] Gyr
Other designations
30 Vul, BD+24°4229, FK5 3657, GC 28920, HD 197752, HIP 102388, HR 7939, SAO 89084[10]
Database references
SIMBAD	data

The variable radial velocity of this system was announced in 1922 by W. W. Campbell. It is a single-lined spectroscopic binary system with an orbital period of 6.86 years and an eccentricity of 0.38. The a sin i value is 149 ± 4 Gm (1.00 ± 0.03 AU), where a is the semimajor axis and i is the orbital inclination. This provides a lower bound on the true semimajor axis.[6]

The visible component is an aging giant star with a stellar classification of K1 III[3] and an estimated age of 4.20[7] billion years old. Having exhausted the supply of hydrogen at its core, the star has expanded to 22[1] times the Sun's radius. It has 1.55[7] times the mass of the Sun and is radiating 173[1] times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,498 K.[1]