WD 0806−661


WD 0806−661 is a wide binary system of a white dwarf and a Y-type sub-brown dwarf, located in constellation Volans at 63 light-years from Earth. The companion was discovered in 2011. It has the largest actual and apparent separation of any known planetary-mass object.

Discovery

Component B was discovered in 2011 with Spitzer Space Telescope. Its discovery paper is Luhman et al., 2011. At the time of its discovery, WD 0806−661 B was the coldest "brown dwarf" that has ever been found, with a temperature of only 27–80 °C, which is similar to some hot areas of Earth.

The companion

The secondary is a sub-brown dwarf with a mass between 7 and 9 and a temperature between 325–350 Kelvin. The spectral type of this object was estimated to be Y1 as it was detected with the Hubble Space Telescope in near-infrared wavelengths. The color of this object suggest that it is metal-poor. The metal-poor composition of the companion cloud explain the DQ spectral type of the primary white dwarf. Hydrogen-deficient AGB stars might evolve into DB white dwarfs and then into DQ white dwarfs as they cool down.