Washington: 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.
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.
“We decided to go several steps back in the process when (brown dwarfs) are really hidden,” said David Barrado of the Centro de Astrobiologia in Madrid, Spain, lead author of the paper on the discovery.
“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,” he added.
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.