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Infrared image of the dusty brown dwarf binary HD 130948BC (upper left in orbit around a young sun-like star, seen to the lower right. Credit: Trent Dupuy and Michael Liu (Institute for Astronomy)
Weighing Brown Dwarfs
Manoa Associate Astronomer Michael Liu and Graduate Assistant Trent Dupuy have used ultra-sharp images obtained with the Keck Telescope and Hubble Space Telescope to determine for the first time the masses of the coldest class of "failed stars” or brown dwarfs. With masses as light as three percent the mass of the sun, these are the lowest mass free-floating objects ever weighed outside the solar system. The observations are a major step in testing the theoretical predictions of objects that cannot generate their own internal energy, both brown dwarfs and gas-giant planets.
Brown dwarfs are a class of objects that represent the missing link between the lowest-mass stars and the gas-giant planets, such as Jupiter and Saturn. Brown dwarfs are the faintest and coolest objects that can be directly observed outside the solar system. They emit as little as about 1/300,000 the energy of the sun and have surface temperatures comparable to the inside of a pizza oven (800° F), more than 9,000° F cooler than the surface of the sun.
"Mass is the fundamental parameter that governs the life-history of a free-floating object, and thus after many years of patient measurements, we are delighted to report the first masses of the very faintest, coldest brown dwarfs," says Liu. "After weighing these tiny, dim, cold objects, we have confirmed that the theoretical predictions are mostly correct, but not entirely so."