Astronomers have found a planet that may have formed like a star — through gravitational collapse. Kamen Todorov of Pennsylvania State University in University Park and his colleagues spotted a planet 5–10 times the mass of Jupiter orbiting a brown dwarf — a star too small to ignite by fusion.
The brown dwarf is only about one million years old, so its companion is too young to have slowly accreted from the dwarf's disk of dust and gas. Yet the planet is much too big to have quickly collapsed from a large lump in a dwarf's modest disk.
The authors suggest that the dwarf and its planet formed unusually, in the same way that binary star systems do — with a vast, primordial gas cloud fragmenting and collapsing gravitationally into two objects.
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Astrophysics: The odd couple. Nature 464, 961 (2010). https://doi.org/10.1038/464961d
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DOI: https://doi.org/10.1038/464961d
