We didn't expect to see flaring from such a lightweight object. This is really the mouse that roared. The energy emitted in the brown dwarf flare was comparable to a small solar flare, and was a billion times greater than observed X-ray flares from Jupiter. The flaring energy is believed to come from a twisted magnetic field. LP 944-20 is about 500 million years old and has a mass about 60 times that of Jupiter, or 6 percent of that of the Sun.
Brown dwarfs have too little mass to sustain significant nuclear reactions in their cores.
Their primary source of energy is the release of gravitational energy as they slowly contract.