A sub-brown dwarf, or planetary-mass brown dwarf, is an astronomical object that formed in the same manner as stars and brown dwarfs (i.e. through the collapse of a gas cloud) but that has a mass below the limiting mass for thermonuclear fusion of deuterium (about 13 Jupiter masses). Some claim that sub-brown dwarves may be free-floating planets, whereas others call them planetary-mass brown dwarfs.
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