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The Honolulu Advertiser

Posted on: Friday, May 17, 2002

Scientists gather on Big Island to debate brown dwarfs

By Jan TenBruggencate
Advertiser Science Writer

Less than 10 years ago, astronomers had not even detected what is known as a "brown dwarf," but next week 150 scientists from 16 nations will meet on the Big Island to discuss their research on these curious bodies in space.

Hawai'i has played a major role in the growing understanding of brown dwarfs, since it takes giant telescopes like the ones atop Mauna Kea to pick them out against the backdrop of space. The conference at the Outrigger Waikoloa will investigate how these objects form, how they evolve and where they are found.

Perhaps more importantly, they will discuss how to define them, since astronomers do not agree precisely on what a brown dwarf is.

It is generally conceded that a brown dwarf is an object in space that is somewhere between a giant planet and a star.

A star, such as our sun, has such great mass that nuclear reactions occur at its core. That's what makes stars glow. University of Hawai'i astrophysicist Eduardo Martin said astronomers agree that if an object in space has less than 7 percent of the mass of our sun, it dips into the category of a brown dwarf.

But there is less agreement on the lower boundary between a planet and a brown dwarf.

The largest planet in our solar system is the gas giant known as Jupiter.

Some argue that anything with 13 or more times the mass of Jupiter is a brown dwarf. That would be enough mass to generate powerful nuclear reactions.

Others suggest that a weak nuclear reaction, which produces certain categories of detectable elements, can be used to identify a brown dwarf.

Still others argue that it has more to do with whether the object is associated with a star or is drifting free in space.

Martin said the top scientists in the field will lead a special session of the conference Monday night to try to reach agreement on the issue of where to draw the line between planet and brown dwarf.

"This is the best meeting that has ever been held to have this discussion," he said.

The University of Hawai'i Institute for Astronomy is putting on the conference with the help of several Big Island telescopes, NASA, the Hawai'i Island Economic Development Board, the UH-Hilo Conference Center and the Hawai'i Tourism Authority.