Draft:H dwarf
Brown dwarf or planet with atmospheric hydrocarbons
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An object with a spectral type H (also called H dwarf or hydrocarbon brown dwarf)[1] is either a brown dwarf or a free-floating planetary mass object. They have a extremely low-mass for brown dwarfs (under the deuterium burning limit), and are predicted to be colder than Y dwarfs.[1]
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Comment: interesting; would be great to see some secondary sources. Astropedian (talk) 11:14, 1 March 2026 (UTC)
Characteristics
The spectral type H was first suggested in June 2025 by astronomers, Kevin Luhman and Catarina Alves de Oliveira after they discovered two unusual brown dwarfs.[1] They are characterized by a presence of unknown aliphatic hydrocarbon in their atmospheres, and an absorption line at 3.4-3.5 μm.[1]
H-type dwarfs have very low masses for brown dwarfs with a mass between 2 and 10 MJ.[1] The least massive H-type dwarf is approximately the same mass as Jupiter, making them the least massive brown dwarf spectral type.[1] However, the least massive L-type dwarfs such as 2M1207 b have similar properties to H-type dwarfs.[1]
Only two candidate H-type dwarfs have been found which are designated LRL 11001, and LRL 11003.[1] There absorption lines are similar to the diffuse interstellar medium (also known as the ISM).[1] Although, these two brown dwarfs may be H-type dwarfs they also have a similar spectra and properties to L-type dwarfs.[1]
Location
Using the James Webb Space Telescope (abbreviated as JWST), Luhman and Alves de Oliveira were able to identify two potential H-type dwarfs in the IC 348 star-forming region.[1] No other H-type dwarfs have been discovered in other regions, but there are predicted to exist in NGC 2024 (also referred to as the Flame Nebula), and the TW Hydrae association.[1]