brown dwarf, in astronomy, celestial body that is larger than a planet but does not have sufficient mass to convert hydrogen into helium via nuclear fusion as stars star, hot incandescent sphere of gas, held together by its own gravitation, and emitting light and other forms of electromagnetic radiation whose ultimate source is nuclear energy.
..... Click the link for more information. do. Also called "failed stars," brown dwarfs form in the same way as true stars (by the contraction of a swirling cloud of interstellar matter interstellar matter, matter in a galaxy between the stars, known also as the interstellar medium. Distribution of Interstellar Matter

Compared to the size of an entire galaxy, stars are virtually points, so that the region occupied by the
..... Click the link for more information. ). True stars have enough mass (greater than 0.084 times that of the sun) to compress their core until the increasing temperature and pressure ignite the hydrogen fusion reaction, but brown dwarfs have only a relatively short period of deuterium (heavy hydrogen) burning before they cool and fade. Their coolness gives brown dwarfs two distinguishing characteristics: One is that most of the radiation they emit is in the infrared part of the spectrum; the other is that brown dwarfs can be distinguished by traces of lithium in their spectrum because, unlike true stars, brown dwarfs never get hot enough to burn the lithium that was in the interstellar cloud as it condensed.

Although they should exist in large numbers, brown dwarfs are difficult to find using conventional astronomical techniques because they are dim compared with true stars. A number of brown dwarfs have been identified, the first in the Pleiades Pleiades , in astronomy, famous open star cluster in the constellation Taurus; cataloged as M45. The cluster consists of some 500 stars, has a diameter of 35 light-years, and is 400 light-years distant from the earth.
..... Click the link for more information. star cluster in 1995. The first X-ray-emitting brown dwarf was detected in Chamaeleon dark cloud number I in 1998. A year later, several so-called methane dwarfs were discovered; these are thought to be older brown dwarfs that have cooled sufficiently over billions of years so that large amounts of methane could form in their atmospheres. The closest brown dwarf to Earth, Epsilon Indi B, less than 12 light-years from the Sun, was discovered in 2003.

Brown dwarfs belong to the "T dwarf" category of objects straddling the domain between stars and giant planets. Because brown dwarfs are typically 10–80 times the mass of Jupiter, some of the large extrasolar bodies discovered orbiting stars may be brown dwarfs rather than giant Jupiterlike planets. Observations of 100 young brown dwarfs in the Orion Nebula in 2001 strongly supported the theory that they originate as failed stars; many of the brown dwarfs were surrounded by disks of dust and gas that conceivably could condense and conglomerate to create planets orbiting them. Brown dwarfs are believed to play an important role in the process of stellar evolution stellar evolution, life history of a star, beginning with its condensation out of the interstellar gas (see interstellar matter) and ending, sometimes catastrophically, when the star has exhausted its nuclear fuel or can no longer adjust itself to a stable
..... Click the link for more information. . They are a component of the dark matter dark matter, material that is believed to make up (along with dark energy) more than 90% of the mass of the universe but is not readily visible because it neither emits nor reflects electromagnetic radiation, such as light or radio signals.
..... Click the link for more information. that along with dark energy dark energy, repulsive force that opposes the self-attraction of matter (see gravitation) and causes the expansion of the universe to accelerate. The search for dark energy was triggered by the discovery (1998) in images from the Hubble Space Telescope of a distant
..... Click the link for more information. may account for more than 90% of the mass of the universe.

brown dwarf

Astronomical object intermediate in mass between a planet and a star. Sometimes described as failed stars, brown dwarfs are believed to form in the same way as stars, from fragments of an interstellar cloud that contract into gravitationally bound objects. However, they do not have enough mass to produce the internal heat that in stars ignites hydrogen and establishes nuclear fusion. Though they generate some heat and light, they also cool rapidly and shrink; they may differ from high-mass planets only in how they form.

brown dwarf [¦braün ¦dwȯrf]

(astronomy)

A starlike body whose mass is too small (less than about 8% that of the sun) to sustain nuclear reactions in its core. Also known as black dwarf; failed star; infrared dwarf; lilliputian star; substellar object; super-Jupiter.

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No references found			Byline: ANI Washington, November 24 (ANI): NASA's Spitzer Space Telescope has contributed to the discovery of the youngest brown dwarf ever observed, a finding that, if confirmed, may solve an astronomical mystery about how these cosmic misfits are formed. NASA's Spitzer telescope observes youngest brown dwarf ever observed by Asian News International Though researchers imaged an exoplanet around a brown dwarf in 2004, no one has recorded an image of a planet orbiting a sunlike star. Astronomers snap extrasolar image: shot may be the first of an ... by Cowen, Ron / Science News Air Force lieutenant colonel explains the general principles and development of optical, gamma-ray, X-ray, infrared, and ultraviolet astronomy observatories to study stars, planets, moons, asteroids, brown dwarfs, dark matter, and big bang cosmology. Spacecraft for astronomy by SciTech Book News			Brower, David Brower, Lincoln P. Browere, John Henri Isaac brown brown acid Brown Algae Brown and Sharpe gage Brown and Sharpe gauge Brown and Sharpe Wire Gauge brown ass brown bast Brown Bear brown blight brown blotch brown canker Brown Carpathian Cattle brown clay brown clay ironstone Brown Coal brown coat Brown County Brown County State Park Brown Deer Brown Deer Park Brown Desert-Steppe Soils brown dwarf brown fat cell brown felt blight Brown Fish Owl Brown Forest Soils Brown Hematite brown induration brown iron ore Brown Latvian Breed brown lead oxide brown leaf rust brown lignite brown lung disease brown mica brown paper bag bug brown patch brown petroleum Brown Rat brown recluse spider brown rice brown root brown root rot brown rot brown seaweed Brown Shirt Brown shirts			Brown County, Wisconsin Brown cow Brown crab brown creeper brown creeper brown creeper brown creepers brown creepers brown creepers Brown Crystal brown cup Brown Daily Herald, Inc. Brown Daisy Brown Deer Brown Deer Brown Deer High School Brown Deer Middle School Brown Deer Park Brown Deer School District Brown Deer, Wisconsin Brown Deer, Wisconsin brown dental stains Brown dermatome Brown dermatome Brown dermatome Brown Desert-Steppe Soils brown dog tick Brown Dots Brown dragon Brown Driver Briggs Gesenius brown dwarf Brown dwarf star Brown dwarf star Brown dwarf star Brown dwarfs Brown dwarfs Brown dwarfs brown dwarves brown dwarves brown dwarves brown ear tick Brown earth Brown Economic Consulting Inc Brown Electronic Article Review Service Brown Electronic Lab Brown Environmental Action Network Brown Environmental Leadership Lab Brown eumelanin Brown eumelanin Brown eumelanin Brown eumelanin Brown eye Brown Eyed Girls Brown Eyed Woman Brown Falcon Brown Family Environmental Center brown fat brown fat brown fat brown fat brown fat cell