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WISE satellite already spots two brown dwarfs

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WISE brown dwarfsMIAMI—A satellite launched by NASA in 2009 to map the sky in infrared wavelengths is beginning to deliver on one of its ancillary promises, the mission’s scientific leader said here at the semiannual meeting of the American Astronomical Society. Edward Wright, a University of California, Los Angeles, astronomer who serves as principal investigator for the Wide-field Infrared Survey Explorer (WISE), said in a talk Monday that the spacecraft has already discovered at least two cool, substellar objects known as brown dwarfs.

One of the brown dwarfs, dubbed WISE 2, appears to be as cold as any that are known. It may even be colder, Wright said, than the brown dwarfs recently found by the UKIDSS survey, which are estimated to be in the neighborhood of 500 Kelvin, but the exact temperature of WISE 2 is uncertain (as are the temperatures of the UKIDSS objects). WISE 1 is a bit warmer, Wright said: "We think this is about an 800-Kelvin object."

Brown dwarfs are objects larger than planets and smaller than true stars, although the boundaries between the three groups are somewhat blurry. A strictly mass-based definition holds that brown dwarfs are too small (less than about 75 times Jupiter’s mass) to fuse hydrogen in their cores, as stars do, but are large enough (more than about 13 Jupiter masses) to fuse deuterium, a heavy isotope of hydrogen.

They are thought to be numerous, and indeed hundreds of brown dwarfs have already been found. But surveys to date have not been able to find the dimmest, coolest brown dwarfs that theory predicts—those that have temperatures of just a few hundred Kelvin. But WISE’s infrared channels are sensitive to that population and should be able to assess just how common those cool dwarfs are.

Wright later said that whereas the spectra of WISE 1 and WISE 2 are unambiguous, the spacecraft has found many more objects that may also be brown dwarfs. Confirmation of those will await follow-up observations, which the group has proposed on the Spitzer Space Telescope. Distances to the two new brown dwarfs are not known, Wright added, but WISE should be able to turn up bundles of such objects in its 10-month mission, some of which may be closer to the solar system than Proxima Centauri, the nearest known star to the sun.

Artist’s conception of (left to right) the sun, a low-mass star, a warm brown dwarf, a cool brown dwarf and Jupiter: NASA/IPAC/R. Hurt

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  1. 1. Kristoffer 5:07 pm 05/27/2010

    They prefer to be called Little Stars.

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  2. 2. rhehudio 6:14 pm 05/27/2010

    Here’s one for ya, if iron is the death of a star, then why are all the planets filled with iron core’s? my thought is that a star explodes all the time. when it creates iron, it expels it violently, but still retains it’s mass. I think Systems are actually mass points in the area, with an atom smasher creating iron left and right. once a star explodes, mass creates gravity, and slowly but surely the system reforms as another star. I think the big bang is a repeating occurance. There put that in your pipe and smoke it.

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  3. 3. lithiumdeuteride 6:55 pm 05/27/2010

    I think you’ve done enough smoking for the both of us.

    Planets are made of iron because planets are formed from the debris clouds caused by the destruction of previous-generation stars, which manufacture iron via nucleosynthesis.

    What is a ‘mass point’, other than a black hole? Massive objects like stars and planets have volumes associated with them; they are not points.

    "Once a star explodes, mass creates gravity". That is technically true, but misses the point. Mass *always* creates gravity. It does not matter whether that mass is in the form of a star or a planet or a fungus.

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  4. 4. Habbycabbie 3:44 pm 05/28/2010


    The plural of Dwarf is Dwarves.

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  5. 5. Wayne Williamson 4:23 pm 05/28/2010

    cool discoveries….i think number of "brown dwarfs" far out number the number of stars…i’m left wondering why they can’t determine the distance to them…

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  6. 6. jmatson 5:31 pm 05/28/2010

    Both are plural of dwarf, but Webster’s dictionary prefers "dwarfs":

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  7. 7. qraal 6:37 pm 05/28/2010

    Would be fascinating to find a brown-dwarf system closer to Sol than Proxima. One wonders if a 500 K dwarf could warm a moon or two sufficiently for interesting biology?

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  8. 8. jtdwyer 9:45 pm 05/28/2010

    Wayne Williamson – That is an interesting question. As I understand, distance is often determined by the degree of spectral shift for objects of known chemical composition – mapping the shifted spectral lines to the known emission spectrum.

    The article states: "whereas the spectra of WISE 1 and WISE 2 are unambiguous, the spacecraft has found many more objects that may also be brown dwarfs", implying that the spectral emissions are being used to confirm the composition of brown dwarfs. It would seem that shifted spectra could be used to determine distance. Maybe that simply hasn’t been done yet?

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