A new approach to finding undiscovered objects buried in immense
astronomical databases has produced an early and unexpected payoff: a new
instance of a hard-to-find type of star known as a brown dwarf.

Scientists working to create the National Virtual Observatory (NVO), an
online portal for astronomical research unifying dozens of large
astronomical databases, confirmed discovery of the new brown dwarf recently.
The star emerged from a computerized search of information on millions of
astronomical objects in two separate astronomical databases. Thanks to an
NVO prototype, that search, formerly an endeavor requiring weeks or months
of human attention, took approximately two minutes.

NVO researchers emphasized that a single new brown dwarf added to a list of
approximately 200 known brown dwarfs isn’t as scientifically exciting as the
timing of the new discovery and the tantalizing hint it offers to the
potential of NVO. The discovery came at a stage when organizers were simply
hoping to use NVO to confirm existing science, not make new findings.

“This was just supposed to be a feasibility demo. We just wanted it to find
all the brown dwarfs that others could find, to show that this was a valid
approach,” said Alex Szalay, director of the NVO project and Alumni
Centennial Professor of Astronomy in the Johns Hopkins Krieger School of
Arts and Sciences. “This was the first time we turned the NVO devices on,
and they immediately yielded a new discovery from data that’s been publicly
available for at least a year and a half.”

According to Szalay, that’s just the kind of finding organizers are hoping
will start pouring from the NVO in a few more years: revelations available
in data already gathered by observatories, probes and surveys, but left
undiscovered because new technology is pouring new data so rapidly into a
variety of different databases.

The new discovery came from one of three scientific prototypes NVO
scientists presented at the January 2003 meeting of the American
Astronomical Society. NVO partners at the California Institute of
Technology’s Infrared Processing and Analysis Center (IPAC) implemented the
software for the prototype that found the new brown dwarf. Principal
contributors to the demonstration project included Davy Kirkpatrick and
Bruce Berriman, the demonstration project leader, both from IPAC.

Different astronomical surveys and probes look at the sky with instruments
sensitive to different portions of the electromagnetic spectrum. Often, the
specific part of the spectrum measured by a particular instrument can be the
key to gaining insights to a particular class of objects or certain
properties of those objects. But some of the oddest characters in the
cosmos, such as brown dwarfs, only really start to stick out from the
enormous background of the universe when looked at by different instruments
that show how the objects appear at points across the electromagnetic
spectrum.

Among the key ingredients NVO will provide for multiple database searches
is a standard way of delivering data, according to NVO co-director Roy
Williams, a senior scientist at Caltech.

“The brown dwarf emerged from looking at two independent surveys together,
and it’s the standard way of delivering the data from the surveys that
enables them to be federated and us to find out what’s in there,” Williams
said. “It’s hard to identify the brown dwarfs in either survey, but if you
put them together, they start to come out.”

“People can do these kinds of investigations without NVO,” said Bob
Hanisch, a Space Telescope Science Institute astronomer and NVO project
manager. “But with the NVO, they’ll run much more rapidly and effectively.
Many projects that astronomers can’t take on now because of the sheer volume
of sifting and searching involved will suddenly become much more feasible.”

Astronomers and computer scientists from 17 research institutions are
currently collaborating to build the framework for the NVO, which is funded
by a five-year, $10 million Information Technology Research Grant from the
National Science Foundation.

For the brown dwarf project, researchers wanted to show that they could use
NVO connections they had built between two large databases — the Sloan
Digital Sky Survey (SDSS) and the Two Micron All Sky Survey (2MASS) — to
confirm brown dwarfs already identified through previous non-NVO comparison
of those databases.

Brown dwarfs were, for many years, a missing link in astronomers’ model of
star formation. The first definitive detection of a brown dwarf didn’t come
until 1995, when a team at Johns Hopkins and Caltech announced that they had
firmly identified one. Brown dwarfs are hard to detect because they’re
small, cool stars, sometimes described as “failed stars,” with less than 8
percent the mass of the sun. That’s still hundreds of times the mass of the
gas giant planet Jupiter, but not massive enough to create the
self-sustaining nuclear reaction that powers larger stars. As a result, a
brown dwarf grows cooler and dimmer as it ages, making it increasingly
difficult for astronomers to detect.

To find the new brown dwarf and two already-recognized brown dwarfs, the
NVO project searched through information on 15 million astronomical objects
in SDSS and 160 million objects in 2MASS. The prototype found that in the
region of sky currently covered by both surveys (about 0.4 percent of the
night sky) the two databases had 300,000 astronomical objects in common or
very likely to be references to the same physical object.

Additional selection criteria based on the brightness differences of the
objects between the SDSS and 2MASS catalogs suggested that the NVO prototype
had found seven new brown dwarf candidates, but followup observations and
human analysis whittled that list down to three, yielding the confirmed
brown dwarf and two more candidates that have yet to be spectroscopically
verified. Szalay said that was a fine success rate, given the magnitude of
the data searched.

“We narrowed it down from tens of million of objects, to a few hundred
thousand, to a handful,” Szalay explained. “This is truly remarkable.”

“The discovery of the new brown dwarf is a wonderful example of what can be
done with powerful tools to mine large databases,” said Rich Kron,
astronomer at Fermilab and the University of Chicago and an SDSS
spokesperson. “Correlating different maps of the sky greatly expands the
‘discovery space’ of each survey. No doubt, many more remarkable objects
still remain to be found.”

“The combined, multi-wavelength view of the universe is definitely more
than the sum of its parts,” says Roc Cutri, 2MASS project scientist and IPAC
deputy director. “The SDSS and 2MASS data sets are unprecedented resources
for astronomical discovery in their own right, but the synergy realized by
combining these massive data sets opens research possibilities that were
only dreamed of before.”

Brown dwarf expert Kirkpatrick expressed eagerness to apply the new
NVO-based search technique to larger patches of sky as the data becomes
available.

“This method is fully capable of uncovering a colder brown dwarf than any
now known, and I’m looking forward to working with NVO products in order to
find it,” Kirkpatrick said.

SDSS and 2MASS images of the new brown dwarf are online at:
http://www.jhu.edu/news_info/news/home03/mar03/nvo.html .

Related Web sites:
Original announcement of NVO (10/29/01):
http://www.jhu.edu/news_info/news/home01/oct01/virtual.html

NVO Web page: http://us-vo.org/