A helium planet is a theoretical type of planet that may form via mass loss from a low-mass white dwarf. Ordinary gas giants such as Jupiter and Saturn consist primarily of hydrogen, with helium as a secondary component. A helium planet might form in an environment where all the hydrogen has been processed to helium or other heavier elements by nuclear fusion.
One scenario involves an AM CVn type of symbiotic binary star composed of two helium core white dwarfs surrounded by a circumbinary helium accretion disk formed during mass transfer from the less massive to the more massive white dwarf. After it loses most of its mass, the less massive white dwarf may approach planetary mass.
Helium planets are predicted to have roughly the same diameter as hydrogen–helium planets of the same mass.
- "All Planets Possible". Astrobiology Magazine. 2007-09-30.