39 Draconis is a wide

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

system in the northern circumpolar constellation of Draco. It has the

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. ...

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 an apparent visual magnitude of 5.0. Parallax measurements made by the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

spacecraft put it at a distance of 184 light-years, or 56 parsecs away from the Sun. The system is moving closer to the Earth with a heliocentric

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of -24.5 km/s. The two components of 39 Draconis have an

angular separation Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

of and take almost 4,000 years to orbit each other. The primary star is an early

A-type main-sequence star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

, having 2.12 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

with a visual magnitude of 5.06 The secondary is a magnitude 8.07 F-type main-sequence star, and has 1.18 times the mass of the Sun. The 8th-magnitude star HD 238865 is listed in double star catalogues as component C. It is separated from the other two stars by and lies at about the same distance. It is itself a

spectroscopic binary A binary star is a system of two star, stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separa ...

with an F8 primary and a red dwarf secondary orbiting every 2.7 days.

References

{{DEFAULTSORT:39 Draconis A-type main-sequence stars F-type main-sequence stars Binary stars Draco (constellation) Draconis, 39 Durchmusterung objects Draconis, b 170073 090156 6923