Spitzer Telescope Observes Baby Brown Dwarf

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http://www.jpl.nasa.gov/news/news.cfm?release=2009-174

Spitzer Telescope Observes Baby Brown Dwarf
Jet Propulsion Laboratory
November 23, 2009

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 .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney...@jpl.nasa.gov

2009-174