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Defining a Brown Dwarf / Planet Boundary

23 Jan 2018, 18:01 UTC
Defining a Brown Dwarf / Planet Boundary
(200 words excerpt, click title or image to see full post)

A paper that crossed my desk this morning proves timely in light of our recent discussions about brown dwarfs. Specifically, the question of when to declare an object a planet or a brown dwarf has come up, with the cutoff often cited at about 13 Jupiter masses. Now I see that Johns Hopkins’ Kevin Schlaufman is proposing a cutoff somewhere closer to 10 Jupiter masses, but the idea takes us beyond mass as the determinant of the object’s status.

We tend to turn toward the IAU Working Group on Extrasolar Planets for our ideas on the planet/brown dwarf distinction, though the fact that we can find objects with 10 times Jupiter’s mass both in orbit around stars and also in isolation makes the definition a challenging one. The IAU has defined a planet as an object with a mass below the limiting mass for deuterium fusion that orbits a star or stellar remnant. Objects above this limiting mass have been defined as brown dwarfs, no matter how they formed or where they are located. This is where the 13 Jupiter mass cutoff comes from, although other models have also been proposed.
Image: Johns Hopkins astrophysicist Kevin Schlaufman has proposed a ...

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