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Beyond Earthly Skies

Classifying Planets, Brown Dwarfs & Stars

11 Jul 2015, 23:00 UTC
Classifying Planets, Brown Dwarfs & Stars
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Figure 1: Artist’s impression of a giant planet.Stars are objects with sufficient mass to sustain hydrogen fusion in their cores, while sub-stellar objects (i.e. brown dwarfs and planets) have masses below what is required to sustain hydrogen fusion. The mass boundary between stars and sub-stellar objects lie at about 80 times Jupiter’s mass and seems to be quite clear. However, the mass boundary between what is considered a planet and what is considered a brown dwarf is unclear. One definition is that if a planet is defined as a sub-stellar object that has not undergone deuterium burning at any point in its life; then the mass boundary between planets and brown dwarfs is about 13 times Jupiter’s mass. Unfortunately, this distinction is weak because deuterium burning only occurs for a brief period and has a negligible impact on the future evolution of a brown dwarf.Hatzes & Rauer (2015) propose a new definition for planets, brown dwarfs and stars by presenting the mass-density relationship for objects ranging from planets with ~0.01 times Jupiter’s mass through stars with more than 80 times Jupiter’s mass. The mass-density diagram shows 3 distinct regions. Objects below 0.3 times Jupiter’s mass show considerable scatter, objects between ...

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