Brown dwarf

Rare card · No. 43581

Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ)—not big enough to sustain nuclear fusion of hydrogen into helium in their cores, but massive enough to emit some light and heat from deuterium fusion, 2H, an isotope of hydrogen with a neutron as well as a proton, that can undergo fusion at lower temperatures. The most massive ones (> 65 MJ) can fuse lithium (7Li). Astronomers classify self-luminous objects by spectral type, a distinction intimately tied to the surface temperature -- brown dwarfs occupy types M (2100–3500 K), L (1300–2100 K), T (600–1300 K), and Y (< 600 K). As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. The "brown" in brown dwarf was meant to name a color between red and black. To the naked eye, most brown dwarfs would...

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