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An accretion disk is a structure (often a circumstellar disk) formed by diffuse material [a] in orbital motion around a massive central body. The central body is most frequently a star . Friction , uneven irradiance, magnetohydrodynamic effects, and other forces induce instabilities causing orbiting material in the disk to spiral inward toward ...
About 6% of white dwarfs show infrared excess due to a disk around a white dwarf. [66] In the past only a relative small sample of white dwarf disks was known. [67] Due to advances in white dwarf detection (e.g. with Gaia or LAMOST) and improvement of WISE infrared catalogs with unWISE/CatWISE, the number has increased to hundreds of candidates.
The disk around the white dwarf is too large (~1-10 solar radii) to be formed by a small minor planet, which was tidally disrupted inside the Roche Radius. The team was also able to exclude accretion of material from a companion star or brown dwarf. [4] The most plausible explanation is an evaporating giant planet, orbiting close to the white ...
WD 2317+1830 (SDSS J231726.72+183049.6) is one of the first white dwarfs with lithium detected in its atmosphere. The white dwarf is surrounded by a debris disk and is actively accreting material. Researchers suggest that the presence of alkali metals indicates the accretion of crust material.
Leaving aside formation from the accretion disk surrounding the white dwarf, there are two ways a planet could end in a close orbit around stars of this kind: by surviving being engulfed by the star during its red giant phase, and then spiralling inward, or inward migration after the white dwarf has formed. The former case is implausible for ...
Matter is stripped from a white dwarf (sphere at lower right) orbiting within the innermost accretion disk surrounding 1ES 1927+654's supermassive black hole.
[19] [20] If the accretion continues long enough, the white dwarf may eventually approach the Chandrasekhar limit. The white dwarf companion could also accrete matter from other types of companions, including a subgiant or (if the orbit is sufficiently close) even a main sequence star. The actual evolutionary process during this accretion stage ...
Dwarf nova HT Cas seen in outburst (mag ~13.4) on November 2, 2010. A dwarf nova (pl. novae), or U Geminorum variable, is one of several types of cataclysmic variable star, consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion. Dwarf novae are dimmer and repeat more ...