39 Draconis

39 Draconis is a wide binary star system in the northern circumpolar constellation of Draco. It has the Bayer designation b Draconis, while 39 Draconis is the Flamsteed designation. This system is visible to the naked eye as a dim, white-hued point of light with a combined apparent visual magnitude of 5.0.^[1] Parallax measurements made by the Gaia spacecraft put it at a distance of 190 light-years, or 58 parsecs away from the Sun. The system is moving closer to the Earth with a heliocentric radial velocity of −24.5 km/s.^[8]

Apparentmagnitude(V)5.06^[3]

Apparentmagnitude(V)8.07^[3]

Evolutionarystagemain sequence^[2][5]

SpectraltypeA1V + F5V^[6]

Quick facts Apparent magnitude (V), Characteristics ...

39 Draconis

Location of 39 Draconis (circled in red)
Observation data Epoch J2000      Equinox J2000
Constellation	Draco[1]
A
Right ascension	18h 23m 54.60689s[2]
Declination	+58° 48′ 02.6667″[2]
Apparent magnitude (V)	5.06[3]
B
Right ascension	18h 23m 54.51639s[4]
Declination	+58° 48′ 06.3674″[4]
Apparent magnitude (V)	8.07[3]
Characteristics
Evolutionary stage	main sequence[2][5]
Spectral type	A1V + F5V[6]
U−B color index	+0.06[7]
B−V color index	+0.10[7]
Astrometry
Radial velocity (Rv)	−24.53±0.23[8] km/s
A
Proper motion (μ)	RA: −37.322[2] mas/yr Dec.: +62.892[2] mas/yr
Parallax (π)	17.1615±0.0631 mas[2]
Distance	190.1 ± 0.7 ly (58.3 ± 0.2 pc)
Absolute magnitude (MV)	+1.31[9]
B
Proper motion (μ)	RA: −41.742[4] mas/yr Dec.: +61.076[4] mas/yr
Parallax (π)	17.2293±0.0219 mas[4]
Distance	189.3 ± 0.2 ly (58.04 ± 0.07 pc)
Absolute magnitude (MV)	+4.32[9]
Orbit[3]
Period (P)	4,000±200 yr
Semi-major axis (a)	6.6±0.3″
Eccentricity (e)	0.553±0.005
Inclination (i)	107.7±0.12°
Longitude of the node (Ω)	179.9±0.10°
Periastron epoch (T)	5671.40±12.08
Argument of periastron (ω) (secondary)	128.0±2.2°
Details
39 Dra A
Mass	2.12[9] M☉
Radius	2.3[10] R☉
Luminosity	27[10] L☉
Surface gravity (log g)	4.04[10] cgs
Temperature	8,630[10] K
Rotational velocity (v sin i)	186[5] km/s
Age	350[11] Myr
39 Dra B
Mass	1.18[9] M☉
Radius	1.15[10] R☉
Luminosity	1.85[10] L☉
Surface gravity (log g)	4.40[10] cgs
Temperature	6,271[10] K
Rotation	5.9 days[12]
Age	2.6[13] Gyr
Other designations
b Dra, 39 Dra, BD+58°1809, HD 170073, HIP 90156, HR 6923, SAO 30949[14]
Database references
SIMBAD	39 Dra
	39 Dra A
	39 Dra B

Close

The two components of 39 Draconis have an angular separation of 6.621″ and take almost 4,000 years to orbit each other.^[3] The primary star is an early A-type main-sequence star, having 2.12 times the mass of the Sun with a visual magnitude of 5.06.^[3] The secondary is a magnitude 8.07^[3] F-type main-sequence star, and has 1.18 times the mass of the Sun.^[9]

The 8th-magnitude star HD 238865 is listed in double star catalogues as component C.^[15] It is separated from the other two stars by 90″ and lies at about the same distance.^[16] It is itself a spectroscopic binary with an F8 primary and a red dwarf secondary orbiting every 2.7 days.^[17][18]