Originally created 03/20/01

Finding necessitates revamped brown dwarf theory



A bunch of "kids" is getting big gold stars from professional astronomers for taking a scientific gamble that is paying big dividends.

Faced with the hard scientific data produced by the students, new theory will have to be formulated to explain their findings.

A team of 14 undergraduate and graduate students used New Mexico's powerful Very Large Array Radio Telescope during a summer project last year to discover radio emissions coming from a brown dwarf star - a star too little to shine.

In a rare coup for a group so young, the students reported the totally unexpected observation in the current issue of the British science journal Nature.

How unexpected was it?

"The radio emission these students discovered coming from this brown dwarf is 10,000 times stronger than anyone expected," said the VLA's Dale Frail, co-author of the Nature paper.

While the discovery is "cool" in its own right, one of the students, Kate Becker of Oberlin College in Ohio, observed that what's really cool is "this is research that probably nobody else would have tried to do because of its low chance of success."

But Becker said the other students and she "had almost nothing to lose" and their gamble struck it rich.

"Everybody we talked to said there was almost no chance that we'd see anything at all," Becker said, noting the students' advisers did agreed that if they did find something, "it would be really exciting."

The students were struggling for a collaborative observation target last summer, and Frail suggested they might zero in on the brown dwarf LP944-20, which recently had emitted a flare of X-rays detected by the orbiting Chandra X-ray satellite observatory.

To their surprise, Frail and other astronomers now acknowledge that the students' discovery will force astronomers to reconsider theories about brown dwarfs, which until now were assumed to be too puny to create a magnetic field big enough to generate radio emissions.

"The presumed internal structure of a brown dwarf will not permit a strong enough magnetic field" to form around the dwarf, explained Frail. "... It looks like we're going to have to re-examine how we believe brown dwarfs work."

Scientists have believed for years that brown dwarfs existed in the nether realm between hot burning stars and planets the size of Jupiter. The objects were first confirmed in 1995 by Shri Kulkarni, a radio astronomer at the California Institute of Technology in Pasadena.

"Many astronomers are surprised at this discovery, because we didn't expect such strong radio emission from this object," says Kulkarni, who is adviser to one of the students, Edo Berger, from Caltech.

The discovery has the students teaching the teachers. Brown dwarfs may not be big enough in mass to ignite into burning fusion energy furnaces like the sun, but apparently some can generate sizable magnetic fields and resultant radio emissions.

"The mere fact that they detected radio emission is remarkable," said Tim Bastian, an astronomer at the Nation Radio Astronomy Observatory in Charlottesville, Va. His organization operates the VLA and other radio telescopes for the National Science Foundation.

Frail said the student project not only revealed what other astronomers had failed to find but opens up a whole new area of research for the VLA.

"We're going to have to study this and other brown dwarfs more extensively with the VLA to answer the questions raised by our summer students' discovery," he said.

Noting that other astronomers had made similar observations with no results, Frail said, "They got very lucky."

In addition to Becker and Berger, the students are: Ian Hoffman, of the University of New Mexico in Albuquerque; Robert Zavala, from New Mexico State University in Las Cruces; and Steven Ball, from New Mexico Tech in Socorro; Melanie Clarke from Carleton College, Northfield, Minn.; Therese Fukuda of the University of Denver; Richard Mellon from Pennsylvania State University; Emmanual Momjian from the University of Kentucky; Nathanial Murphy from Amherst College, Amherst, Mass.; Stacy Teng of the University of Maryland; Timothy Woodruff, of Southwestern University, Georgetown, Texas; and Ashley Zauderer from Agnes Scott College, Decatur, Ga.