Spitzer Telescope Observes Baby Brown Dwarf

JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney.clavin@jpl.nasa.gov

News release: 2009-174 Nov. 23, 2009

Spitzer Telescope Observes Baby Brown Dwarf

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2009-174&cid=release_2009-174

PASADENA, Calif. -- 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.

"We decided to go several steps back in the process when (brown dwarfs) are really
hidden," said David Barrado of the Centro de Astrobiología in Madrid, Spain, lead
author of the paper on the discovery in the Astronomy & Astrophysics journal. "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."

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.

Barrado and his team embarked on an international quest for more information about the
two objects. Their overarching scientific objective was to observe and characterize the
presence of this dusty envelope -- proof of the celestial womb of sorts that would indicate
that these brown dwarfs were, in fact, in their earliest evolutionary stages.

The twins were observed from around the globe, and their properties were measured and
analyzed using a host of powerful astronomical tools. One of the astronomers' stops was
the Caltech Submillimeter Observatory in Hawaii, which captured the presence of the
envelope around the young objects. That information, coupled with what they had from
Spitzer, enabled the astronomers to build a spectral energy distribution -- a diagram that
shows the amount of energy that is emitted by the objects in each wavelength.

From Hawaii, the astronomers made additional stops at observatories in Spain (Calar Alto
Observatory), Chile (Very Large Telescopes) and New Mexico (Very Large Array). They
also pulled decade-old data from the Canadian Astronomy Data Centre archives that
allowed them to comparatively measure how the two objects were moving in the sky.
After more than a year of observations, they drew their conclusions.

"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.

While further study will confirm whether these two celestial objects are in fact proto
brown dwarfs, they are the best candidates so far, Barrado said. He said the journey to
their discovery, while difficult, was fun. "It is a story that has been unfolding piece by
piece. Sometimes nature takes its time to give up its secrets."

These observations were made before Spitzer ran out of its liquid coolant in May 2009,
beginning its "warm" mission.

The paper's other authors are M. Morales-Calderon, Centro de Astrobiología and Spitzer
Science Center; A. Palau and A. Bayo, Centro de Astrobiología; I. de Gregorio-
Monsalvo, European Southern Observatory; C. Eiroa, Universidad Autónoma de Madrid;
N. Huelamo, Centro de Astrobiología; H. Bouy, Instituto de Astrofísica de Canarias and
European Space Agency; O. Morata, Institute of Astronomy and Astrophysics and
National Taiwan Normal University; and L. Schmidtobreick, European Southern
Observatory. More information on the Spitzer Space Telescope is online at
http://spitzer.caltech.edu and http://www.nasa.gov/spitzer .
-end-

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