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Discovery of a Benchmark Brown Dwarf

24 Jul 2016, 22:00 UTC
Discovery of a Benchmark Brown Dwarf
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Figure 1: Artist's impression of a brown dwarf.Brown dwarfs are objects that are not massive enough to sustain hydrogen burning in their cores. As a result, brown dwarfs become gradually less luminous as they cool with time. Nevertheless, without additional information, the evolutionary state of a brown dwarf cannot be known because the mass and age of a brown dwarf are degenerate parameters. For example, an old, massive brown dwarf can appear similar to a young, low-mass brown dwarf. However, if a brown dwarf has a companion star, the presence the companion can help break the mass and age degeneracy.Crepp et al. (2016) present the discovery of a brown dwarf in orbit around a Sun-like star with 0.82 ± 0.04 times the mass and 0.79 ± 0.03 times the radius of the Sun. The star is identified as HD 4747A and it is located ~60 light years away. Combining radial velocity measurements taken over 18 years with astrometric measurements, the brown dwarf around HD 4747A, identified as HD 4747B, is estimated to have ~60.2 times the mass of Jupiter.Figure 2: Radial velocity measurements indicating the presence of HD 4747B. Crepp et al. (2016)The average distance of 4747B from HD 4747A ...

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