Astronomy and Space

59 Draconis

59 Draconis is a star with a likely brown dwarf companion, located 89.3 light-years (27.4 parsecs) away in the constellation Draco. With an apparent magnitude of 5.1, it is faintly visible to the naked eye under good viewing conditions. In Chinese astronomy, this star is known as Tiānzhùsì (天柱四), meaning it is the fourth star of the asterism Tiānzhù (天柱, Celestial Pillar). The stellar classification of 59 Draconis is A9V, indicating that it is an A-type main-sequence star that is generating energy through hydrogen fusion at its core. Other sources classify it as A7V or F0Vs. It has a similar chemical abundance to the Sun. The star is listed as a suspected variable, with pulsations resembling those of Gamma Doradus stars. It is a candidate member of the Ursa Major Moving Group stream, though a 2020 study listed its membership probability as only 33%. It appears to be rotating with an inclination of about 28° to the plane of the sky. The detection of a companion via Doppler spectroscopy was announced in 2006. This object orbits with a period of 28.4 days and has a minimum mass of 25 MJ, in the range of brown dwarfs. Since the inclination of the orbit is unknown, the true mass cannot be determined, and it remains possible that it is a star rather than a brown dwarf. Hipparcos astrometry has set an upper limit on its mass of 0.27 M☉. If confirmed as a brown dwarf, it is within the brown dwarf desert, a range of orbits where few brown dwarfs are found.

Also on this shelf

See also

• ▸Expedition 18
• ▸Double Asteroid Redirection Test
• ▸38 Arietis

Uncatalogued shelf

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