The brown-dwarf desert is a theorized range of orbits around a star on which brown dwarfs cannot exist as a companion object. This is usually up to 5 AU around solar mass stars. The paucity of brown dwarfs in close orbits was first noted between 1998–2000 when a sufficient number of extrasolar planets had been found to perform statistical studies. Astronomers discovered there is a distinct shortage of brown dwarfs within 5 AU of the stars with companions, while there was an abundance of free-floating brown dwarfs being discovered. Subsequent studies have shown that brown dwarfs orbiting within 3–5 AU are found around less than 1% of stars with a mass similar to the Sun.
This desert occurs because if a brown dwarf were to form, it would have to do so at the same time as its companion star. If the brown dwarf formed within 5 AU of its companion star, it would begin migration towards the star and eventually become consumed by the larger star.
It has recently[when?] been observed that very-low-mass binaries could destroy the theory of brown-dwarf deserts. This is because low-mass binaries are seen to orbit within 5AU; however, due to the low mass of the larger companion, this matter is still a topic of debate.
- Hubert Klahr and Wolfgang Brandner (2006). Planet Formation: Theory, Observations, and Experiments. Cambridge University Press. ISBN 0-521-86015-6.
- Marcy, Geoffrey W.; Butler, R. Paul (February 2000), "Planets Orbiting Other Suns", The Publications of the Astronomical Society of the Pacific 112 (768): 137–140, Bibcode:2000PASP..112..137M, doi:10.1086/316516
- Kraus, Adam L. et al. (May 2008), "Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius", The Astrophysical Journal 679 (1): 762–782, arXiv:0801.2387, Bibcode:2008ApJ...679..762K, doi:10.1086/587435
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