16 Vulpeculae

16 Vulpeculae is a binary star system in the northern constellation Vulpecula.^[1] It has a combined apparent visual magnitude of 5.787,^[2] which is near the lower limit of visibility to the naked eye. Based upon an annual parallax shift of 14.71±0.50^[1] as seen from Earth's orbit, it is located about 222 light years away. The system is moving closer to the Sun with a heliocentric radial velocity of about −37 km/s.^[6] It will make its closest approach in about 0.9 million years, coming within 155 light-years (47.42 pc).^[10]

16 Vulpeculae

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Vulpecula
Right ascension	20h 02m 01.43152s[1]
Declination	+24° 56′ 16.9534″[1]
Apparent magnitude (V)	5.787[2] 5.93 + 6.22[3]
Characteristics
Spectral type	F2 III[4]
U−B color index	+0.10[5]
B−V color index	+0.37[5]
Astrometry
Radial velocity (Rv)	−37.00±3.7[6] km/s
Proper motion (μ)	RA: 89.31[1] mas/yr Dec.: 69.44[1] mas/yr
Parallax (π)	14.71±0.50 mas[1]
Distance	222 ± 8 ly (68 ± 2 pc)
Absolute magnitude (MV)	2.47[7]
Orbit[8]
Period (P)	1201 yr
Semi-major axis (a)	2.687″
Eccentricity (e)	0.932
Inclination (i)	79.0°
Longitude of the node (Ω)	84.5°
Periastron epoch (T)	B 1863.7
Argument of periastron (ω) (secondary)	276.5°
Details
16 Vul A
Mass	1.34[9] M☉
Luminosity	31.13[10] L☉
Surface gravity (log g)	3.76±0.14[9] cgs
Temperature	6,888±234[9] K
Metallicity [Fe/H]	0.17[11] dex
Rotational velocity (v sin i)	136.1±6.8[7] km/s
Age	742[9] Myr
Other designations
16 Vul, BD+24° 3977, HD 190004, HIP 98636, HR 7657, SAO 88098[12]
Database references
SIMBAD	data

The pair orbit each other with an estimated period of 1,201 years and an orbital eccentricity of 0.932.^[8] The magnitude 5.93 primary, component A, displays a stellar classification of F2III,^[12] matching an aging F-type giant star. This star is spinning rapidly with a projected rotational velocity of 136 km/s.^[7] This is giving the star an oblate shape with an equatorial bulge that is an estimated 21% larger than the polar radius.^[13] It is 742^[9] million years old with 1.34^[9] times the mass of the Sun. The star is radiating 31^[10] times the Sun's luminosity from its photosphere at an effective temperature of about 6,888 K.^[9]