The grainy appearance of the image on the right is due to a shorter exposure time. This is the first flare at any wavelength detected from a brown dwarf. The energy emitted in the 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 thought to be produced by a twisted magnetic field.
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. Located in the constellation Fornax in the southern skies, LP 944-20 is one of the best studied brown dwarfs because it is only 16 light years from Earth. It is about 500 million years old and has a mass that is about 60 times that of Jupiter, or 6 percent of the sun's mass. Each panel is 5 arcmin on a side.