Astronomers Find Sun's Coolest Neighbors

Brown dwarfs are often thought of as "stellar wannabes." They are failed stars that never got hot enough to ignite the nuclear fusion process that makes stars shine brightly. On the other hand, they tend to be more massive than planets and do not form around a star, as the planets in our solar system did.

"These latest discoveries are merging the fields of stellar astronomy and planetary science," said Adam Burgasser, physics graduate student at the California Institute of Technology, Pasadena, CA. He is leading the hunt for these objects along with Dr. Davy Kirkpatrick, senior staff scientist at the JPL/Caltech Infrared Processing and Analysis Center.

After sorting through millions of celestial objects, Burgasser discovered four brown dwarfs in images taken by a pair of 1.3-meter (51-inch) telescopes near Tucson, AZ, and at Cerro Tololo, Chile. The telescopes, used for the Two-Micron All Sky Survey (2MASS), study near-infrared wavelengths that can't be seen by the naked eye. They sense heat and thus detect heat-emitting objects like stars and galaxies normally hidden by curtains of cold dust. In this case, the brown dwarfs are too cold to be seen in visible wavelengths, but 2MASS was able to detect the small amounts of heat they emit.

Armed with this information, Michael Brown, Caltech assistant professor of planetary astronomy, studied the objects using the Keck Telescope atop Mauna Kea, HI, to look for the presence of methane, a telltale chemical fingerprint of very cool brown dwarfs.

"Methane forms only in objects cooler than 900 degrees Celsius (1,652 Fahrenheit)," Burgasser said. "That's only four times hotter than the maximum setting on a conventional kitchen oven."

"We think these brown dwarfs are only 30 light years away," said Kirkpatrick. "Because our telescopes can only see the closest examples, this means the Milky Way must be brimming with objects like these." The newly discovered brown dwarfs are located in the constellations of Ursa Major (the Big Dipper), Leo, Virgo, and Corvus.

The 2MASS telescopes are in the midst of a 3-1/2-year survey of the entire sky. The survey is designed to catalog one million galaxies, 300 million stars, and other celestial objects throughout our Milky Way galaxy. The 2MASS telescopes actually discovered five methane brown dwarfs, but one of them had been found previously by the Sloan Digital Sky Survey, also supported by NASA and the National Science Foundation.

The 2MASS project is based at the University of Massachusetts, Amherst, where its principal investigator Dr. Michael Skrutskie is a physics and astronomy professor. The JPL/Caltech Infrared Processing and Analysis Center combines and processes 2MASS images into usable data.

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 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 California Institute of Technology, Pasadena, CA.

The current images, and additional 2MASS information and images are available at the following website:

http://www.ipac.caltech.edu/2mass

2MASS information and images are also available at:

http://pegasus.phast.umass.edu