WD 0806−661 (L 97-3, GJ 3483), formally named Maru, is a DQ

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

with an extremely cold Y-type substellar companion (designated "B"), located in the constellation Volans at from Earth. The companion was discovered in 2011, and is the only known Y-type companion to a star or stellar remnant. At the time of its discovery WD 0806-661 B had the largest actual (2500 AU) and apparent separation (more than 2

arcminute A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

s) of any known planetary-mass object, as well as being the coldest directly imaged substellar object then known.

WD 0806-661 B

Component WD 0806-661 B was discovered in 2011 with the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

. Its discovery was announced in the paper ''Luhman et al., 2011''. The secondary has a mass between 7 and 9 and a temperature between . At the time of its discovery, WD 0806−661 B was the coldest "

brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...

" that has ever been found. The object is too faint to acquire a spectrum even with the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

, however the spectral type of this object was estimated to be Y1 based on its detection in Hubble images at near-infrared wavelengths. The photometric colors of this object suggest that it is

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

-poor. The metal-poor composition of the companion could 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. In August 2022, WD 0806-661 and its planetary-mass companion were included among 20 systems to be named by the third

NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) were various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, notably exoplanets. The accepted names would later be cons ...

project. The approved names, proposed by a team from

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

, were announced in June 2023. WD 0806-661 and its companion are named after the Korean words Maru () and Ahra ().

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Simbad — component b
{{DEFAULTSORT:WD 0806-661 Volans Binary stars White dwarfs 3483 J08065373-6618167 Planetary systems with one confirmed planet Maru

WD 0806-661 B

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