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The most common observable evidence of a remnant planetary system is pollution of the spectrum of a white dwarf with metal absorption lines. 27–50% of white dwarfs show a spectrum polluted with metals, [153] but these heavy elements settle out in the atmosphere of white dwarfs colder than 20 000 K.
The supposed planetesimal, WD 1145+017 b, [13] with a 4.5 hour orbit, is being ripped apart by the star and is a remnant of the former planetary system that the star hosted before becoming a white dwarf. [8] [9] It is the first observation of a planetary object being shredded by a white dwarf. Several other large pieces have been seen in orbit ...
WD 0806−661 (L 97-3, GJ 3483), formally named Maru, [9] is a DQ white dwarf with an extremely cold Y-type substellar companion (designated "B"), located in the constellation Volans at 62.7 light-years (19.2 parsecs) from Earth. The companion was discovered in 2011, and is the only known Y-type companion to a star or stellar remnant.
Brown dwarfs start their lives with M-type spectra and will cool through the L, T, and Y spectral classes, faster the less massive they are; the highest-mass brown dwarfs cannot have cooled to Y or even T dwarfs within the age of the universe.
White dwarfs are among the most compact objects in the cosmos, though not as dense as a black hole. Stars with up to eight times the mass of our sun appear destined to end up as a white dwarf.
Van Maanen's star is also the nearest solitary white dwarf [5] First white dwarf with a planet WD B1620−26: 2003 PSR B1620-26 b (planet) This planet is a circumbinary planet, which circles both stars in the PSR B1620-26 system [6] [7] First singular white dwarf with a transiting object WD 1145+017: 2015 Known object is a disintegrating ...
Like other young, hot white dwarfs, G29-38 is thought to have formed relatively recently (600 million years ago) from its AGB progenitor, and therefore the excess was naturally explained by emission from a Jupiter-like brown dwarf with a temperature of 1200 K and a radius of 0.15 solar radius.
White dwarf: HD 49798: 0.0023 0.023 0.25 1,600 km (990 mi) 2021 White dwarfs are stellar remnants produced when a star with around 8 solar masses or less sheds its outer layers into a planetary nebula. The leftover core becomes the white dwarf. It is thought that white dwarfs cool down over quadrillions of years to produce a black dwarf. [14]