![]() The absence of X-rays from LP 944-20 during the non-flaring period is in itself a significant result. A sub-surface flare could heat the atmosphere, allowing currents to flow and give rise to the X-ray flare - like a stroke of lightning." Professor Gibor Basri of the University of California, Berkeley, the principal investigator for this observation, speculated that the flare "could have its origin in the turbulent magnetized hot material beneath the surface of the brown dwarf. Eduardo Martin, also of Caltech and a member of the team. "This is the strongest evidence yet that brown dwarfs and possibly young giant planets have magnetic fields, and that a large amount of energy can be released in a flare," said Dr. The flaring energy is believed to come from a twisted magnetic field. It was a billion times greater than observed X-ray flares from Jupiter. The energy emitted in the brown dwarf flare was comparable to a small solar flare. This is really the 'mouse that roared.'"Ĭhandra image of LP 944-20 before the flare (left) and during the 2-hour X-ray flare (right) "We didn't expect to see flaring from such a lightweight object. Robert Rutledge of the California Institute of Technology in Pasadena, the lead author on the discovery paper to appear in the July 20 issue of Astrophysical Journal Letters. Its diameter is about one-tenth that of the Sun and it has a rotation period of less than five hours.Ĭhandra detected no X-rays at all from LP 944-20 for the first nine hours of a twelve hour observation, then the source flared dramatically before it faded away over the next two hours. It's about 500 million years old and has a mass that is about 60 times that of Jupiter, or 6 percent that of the sun. 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. The bright X-ray flare has implications for understanding the explosive activity and origin of magnetic fields of extremely low mass stars. Chandra recently detected the first flare ever seen from a brown dwarf. But because they are cool, dim objects, they rarely provide much for high-energy astronomers to observe.Ī new image from NASA's Chandra X-ray Observatory may change that. Brown dwarfs intrigue many astronomers because they are poorly understood and probably a very common class of objects. Their primary source of energy is the release of gravitational energy as they slowly contract. Unlike stars, brown dwarfs have too little mass to sustain nuclear reactions in their cores, so they're very dim - less than a tenth of a percent as luminous as the sun. This illustration shows the size of our Sun (left) compared with a brown dwarf (second from left), Jupiter (third from left) and Earth (right).īrown dwarfs are objects smaller than our Sun and most other stars, but larger than gas giant planets like Jupiter and Saturn. ![]()
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