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Today astronomers announced that they have reached an all-
time low – low temperatures, that is. Adam Burgasser and Dr. Davy Kirkpatrick at the California Institute
of Technology (Caltech) in Pasadena, Calif., have identified the coolest body ever imaged outside of the
solar system, a brown dwarf that lies only 19
light years from Earth.

“Brown dwarfs are essentially failed stars,” said Burgasser, a Caltech physics graduate student who
is heading up the
investigation of these objects as his doctoral thesis project.
“They are too small to ignite nuclear reactions in their cores, so they simply fade with time.”

This newest brown dwarf discovery was imaged by the Two-
Micron All Sky Survey, called 2MASS, whose goal is to image the entire sky at near-infrared wavelengths.
2MASS is a collaboration between the University of Massachusetts and the Infrared
Processing and Analysis Center (IPAC), operated by Caltech and
NASA’s Jet Propulsion Laboratory in Pasadena.

2MASS data was compared with existing optical photographs
that were digitized. This comparison revealed that the object
had no associated optical counterpart, implying that it was most likely a very cool object shining
primarily at near-infrared
wavelengths. Burgasser confirmed the object’s status as a brown dwarf by taking its spectral
“fingerprint” using a spectrograph at the 4-meter (160-inch) Victor M. Blanco telescope, located at the
Cerro Tololo Interamerican Observatory in Chile. Ohio State University built the spectrograph.

The optical photographs were obtained as part of the first- generation Palomar Observatory Sky
Survey and were then converted into digital form at the U.S. Naval Observatory in Flagstaff,

The 2MASS discovery image, taken in 1998 during routine
survey operations from the 2MASS southern observatory at Cerro
Tololo, showed that the brown dwarf lay close to a nearby triple star system called Gliese 570ABC,
located in the constellation
Libra. A second 2MASS image taken 14 months later confirmed that the brown dwarf was in fact a
previously undetected fourth member of this system. “Gliese 570ABC moves across the sky very slightly
every year, undetectable with the naked eye but detectable with a telescope,” said Burgasser. “The
triple star and the brown dwarf moved the same distance and in the same direction, which means
they are part of the same stellar family.”

Using the known distance to Gliese 570ABC and the brightness of the brown dwarf, Burgasser and
Kirkpatrick, an IPAC senior
staff scientist and member of the 2MASS team, computed that the object’s temperature must be only
500 degrees Celsius (900
degrees Fahrenheit), or just one and a half times warmer than the maximum setting on a conventional
kitchen oven. “This makes it the coolest star-like object ever imaged beyond our solar
system,” said Kirkpatrick.

The spectral fingerprint that Burgasser obtained shows that the brown dwarf contains methane as
well, a trait also shared by planets such as Jupiter and Saturn but not by stars. Although the new
discovery, now dubbed Gliese 570D, shows methane and is
believed to be roughly the same size as Jupiter, it is believed to be about 50 times more massive. “The
dividing line between planets and stars was once obvious,” said Burgasser, “but we are now finding
objects that really blur that distinction.”

The 2MASS telescopes are in the midst of a 3 1/2-year survey of the entire sky. IPAC’s processing of
the 20 terabytes of raw survey data will create a publicly accessible catalog of 300
million stars and more than 1 million galaxies. Already, 6
percent of the sky — more than 20 million objects — has been
released to the public. Nearly one-half of the sky — almost 200 million objects — will be publicly available
early in 2000.

The 2MASS project is based at the University of
Massachusetts, Amherst. The JPL/Caltech Infrared Processing and Analysis Center combines and
processes 2MASS images into usable data and makes them available to the public.

As part of NASA’s Origins Program, 2MASS is funded by NASA’s Office of Space Science and the
National Science Foundation.
Results from 2MASS will benefit future Origins missions,
including the Space Infrared Telescope Facility and the Next
Generation Space Telescope. JPL manages the program for NASA’s
Office of Space Science, Washington, DC. JPL is a division of

The Cerro Tololo Observatory is operated by the Association of Universities for Research in
Astronomy Inc., under a
cooperative agreement with the National Science Foundation as
part of the National Optical Astronomy Observatories.

The current images, and additional 2MASS information and
images, are available at . More
information and images are also available at .

For more information, contact Burgasser at (626) 397-7014,
e-mail, or Kirkpatrick at (626) 397-7002,

The 2MASS images and artist’s depiction of the Gliese 570
system are available at .

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