Starship Asterisk*

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.

Brown dwarfs are misfits because they fall somewhere between planets and stars in terms of their temperature and mass. They are cooler and more lightweight than stars and more massive (and normally warmer) than planets. This has generated a debate among astronomers: Do brown dwarfs form like planets or like stars?

Brown dwarfs are born of the same dense, dusty clouds that spawn stars and planets. But while they may share the same galactic nursery, brown dwarfs are often called "failed" stars because they lack the mass of their hotter, brighter stellar siblings. Without that mass, the gas at their core does not get hot enough to trigger the nuclear fusion that burns hydrogen -- the main component of these molecular clouds -- into helium. Unable to ignite as stars, brown dwarfs end up as cooler, less luminous objects that are more difficult to detect -- a challenge that was overcome in this case by Spitzer's heat-sensitive infrared vision.

To complicate matters, young brown dwarfs evolve rapidly, making it difficult to catch them when they are first born. The first brown dwarf was discovered in 1995 and, while hundreds have been found since, astronomers had not been able to unambiguously find them in their earliest stages of formation until now. In this study, an international team of astronomers found a so-called "proto brown dwarf" while it was still hidden in its natal star-forming region. Guided by Spitzer data collected in 2005, they focused their search in the dark cloud Barnard 213, a region of the Taurus-Auriga complex well known to astronomers as a hunting ground for young objects.
...
Spitzer's longer-wavelength infrared camera penetrated the dusty natal cloud to observe a baby brown dwarf named SSTB213 J041757. The data, confirmed with near-infrared imaging from Calar Alto Observatory in Spain, revealed not one but two of what would potentially prove to be the faintest and coolest brown dwarfs ever observed.
...
"We were able to estimate that these two objects are the faintest and coolest discovered so far," Barrado said. Barrado said the findings potentially solve the mystery about whether brown dwarfs form more like stars or planets. The answer? They form like low-mass stars. This theory is bolstered because the change in brightness of the objects at various wavelengths matches that of other very young, low-mass stars.

Doum wrote:They are new brown dwarf ok (Cool) 8) . But with the dust cloud still around, can they become star later by continuing their accumulation of dust. To evacuate that dust cloud away from the brown dwarf it must be heat and they are cool. So?? Will they stay brown dwarf or become star?

http://www.centauri-dreams.org/ wrote: How Do Brown Dwarfs Form?
by Administrator on November 24, 2009

<<Now that we are looking forward to the WISE mission (Wide-Field Infrared Survey Explorer) and its investigations into nearby brown dwarfs, it’s startling to realize that we detected the first of these objects as recently as 1995. Today they’re all the rage, particularly among that small band of us obsessed with missions to nearby interstellar space. A cool, dim brown dwarf could be the closest star to our Sun, an obvious target for a future probe once long-haul propulsion options begin to mature.

Brown dwarfs are too cool to trigger hydrogen fusion, so it takes infrared capabilities like those of WISE or the Spitzer Space Telescope to tell us much about these dim objects. A key question has been whether they form like planets or stars. Spitzer may have found the answer in the form of two ‘proto brown dwarfs’ that have been located in a cloud called Barnard 213, a region of the Taurus-Auriga complex where young objects abound. The finding is significant because we’ve never before found a clear case of a brown dwarf in its earliest formative period.

David Barrado (Centro de Astrobiologia, Madrid) describes the thinking that went into finding these objects:

“We decided to go several steps back in the process when (brown dwarfs) are really hidden. During this step they would have an (opaque) envelope, a cocoon, and they would be easier to identify due to their strong infrared excesses. We have used this property to identify them. This is where Spitzer plays an important role because Spitzer can have a look inside these clouds. Without it this wouldn’t have been possible.”

The result is an infant brown dwarf called SSTB213 J041757, a find that turns out to include not one but two brown dwarfs that are among the faintest and coolest ever observed. Numerous other sites, from the Caltech Submillimeter Observatory in Hawaii to the Calar Alto Observatory in Spain and the Very Large Array in New Mexico took part in the study, which analyzed the dusty envelope around the objects, allowing astronomers to create a spectral density distribution that shows the amount of energy emitted by the objects in each wavelength.

• 
  Here we see a long sought-after view of these very young objects, labeled as A and B, which appear as closely-spaced purple-blue and orange-white dots at the very center of this image. The surrounding envelope of cool dust surrounding this nursery can be seen in purple. These twins, which were found in the region of the Taurus-Auriga star-formation complex, are the youngest of their kind ever detected. They are also helping astronomers solve a long-standing riddle: Do brown dwarfs form more like stars or planets? Credit: NASA/JPL-Caltech/D. Barrado (CAB/INTA-CSIC).

Assuming the work stands up to scrutiny, the implication is that brown dwarfs form more like stars than planets — the spectral density distribution matches other young, low-mass stars.>>