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Hubble Scopes Out Elusive Brown Dwarfs
By Maia Weinstock
Staff Writer
posted: 07:00 am ET
24 August 2000
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Hubble Takes Stock of Distant Brown Dwarfs Astronomers working with NASA's Hubble Space Telescope have imaged a gem-like space-scape in the Orion Nebula, complete with shimmering, diamond-like stars surrounded by bubbling gaseous clouds. The new picture complements what is being touted as the most complete inventory ever of brown dwarfs, star-like gaseous bodies that are relatively small, and unable to shine brightly. In just a short amount of time, a slew of Hubble images and data from both the Orion Nebula and the constellation Perseus have given scientists a much more complete understanding of the formation and abundance of brown dwarfs.Brown dwarfs are hard to detect because they are stellar lightweights, weighing in at just 15 to 80 times the mass of planet Jupiter (one Jupiter-mass is about equal to 318 Earth-masses). As a result of their low masses, brown dwarfs are unable to sustain the nuclear reactions needed to shine like our sun. 
The Hubble Space Telescopes near-infrared camera took this shot of the Trapezium star cluster in the Orion Nebula. The brown dwarfs are the faintest objects in the image. In this false-color image, blue corresponds to more massive stars and red to less massive stars and brown dwarfs. As such, brown dwarfs are too dark to be seen with visible-light cameras including the extra-powerful visible-light camera on board the Hubble Space Telescope. In fact, it took another of Hubbles cameras, which sees light in the near-infrared portion of the electromagnetic spectrum, to view the latest batch of brown dwarfs, which are located in the Trapezium cluster of the Orion Nebula and the IC 348 cluster, in the constellation Perseus. In studying their new brown-dwarf data, astronomers have already learned a great deal about the structure and origin not only of brown dwarfs, but stars and planets as well. "Because brown dwarfs bridge the gap between stars and planets, their properties reveal new and unique insights into how stars and planets form," said Joan Najita, an astronomer with the National Optical Astronomy Observatories (NOAO) who contributed to the brown-dwarf survey.~ In particular, the latest Hubble data add credence to the theory that stars and planets form differently. As astronomers see it, stars form when clouds of gas and dust collapse under heavy gravitational force, whereas planets form when tiny pieces of dust stick together to form larger and larger clumps of rock. Long thought to be stellar rarities, astronomers now think that brown dwarfs are in fact quite common. While finding them -- especially in large clumps -- remains no easy feat, recent finds have shown scientists that brown dwarfs may even be as plentiful in the universe as the more massive stars we can easily see. [quote] Whats more, Najita and her colleagues were able to show that brown dwarfs are more commonly found as isolated "free" objects floating randomly in space, rather than orbiting other stars. This suggests that brown dwarfs are more closely related to stars than large gas planets. Though the astronomers findings are exciting, more detailed studies of brown dwarfs are needed to confirm the objects exact place in the universe. Fortunately, because the Hubble Space Telescope is in good health, scientists have already planned more in-depth brown-dwarf surveys with Hubbles near-infrared instrument.
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