GD 165

GD 165 is a binary white dwarf and brown dwarf system located in the Boötes constellation, roughly 109 light-years from Earth. Neither of the stars have any known exoplanets.

Nomenclature and observation
The system GD 165 is named after Henry L. Giclas, an American Astronomer who lived throughout the 20th century.

GD 165 B was discovered in 1988 by Becklin and Zuckerman at the University of California, Los Angeles. GD 165 B was the first brown dwarf discovered to be cooler than M-Type stars and was initially assigned the spectral type ≥M10. It would not be recognized as a brown dwarf until 1999, when new spectral types L-Type and T-Type for objects cooler than M-type stars were established, reclassifying GD 165 B as L4.

Physical properties
GD 165 A is a pulsating white dwarf with a temperature of about 12,100 K, a mass of 0.64, and a radius of 0.0124. GD 165 A has an extremely dim luminosity of 0.0030, making it completely invisible to the naked eye.

GD 165 B is an L-Type Brown Dwarf with a temperature of about 1,750 K, a mass of about 63, and a radius of 1.00. GD 165B is separated by 123±12 astronomical units from its host white dwarf. It is the second closest spacially resolved brown dwarf after PHL 5038, which has a separation of around 69 AU. It produces almost no light and is completely invisible to the naked eye.