Michael Liu: Brown Dwarfs

Infrared image of the dusty brown dwarf binary HD 130948BC (too left). The binary is in orbit around a young sun-like star seen to the bottom right. This image was obtained with the adaptive optics system on the Keck II Telescope on Maunakea, Hawaii.

Brown dwarfs are not the rabble-rousers of the Universe. They lack enough mass to trigger the nuclear reactions that make stars shine, but have grown too big to be planets. Made entirely of gas, they represent a bridge between the lowest-mass stars and the gas-giant planets, such as Saturn and Jupiter.

Brown dwarfs radiate almost no visible light but their glow and heat can be detected in the infrared spectrum.

Mike Liu uses the Keck and the Canada France Hawaii Telescopes to measure their properties: how distant they are, what their masses are, the amount of energy they generate, and how they evolve.

“These are very high-precision measurements that were impossible when brown dwarfs were first discovered in 1995,” Liu says.

“We know they come in a variety of masses and temperatures, and can range from three times the mass of Jupiter to about 90 Jupiters,” he says. “They can occur on their own and around other stars — in fact, there are more free-floating ones than binary systems.” It’s thought there might be as many brown dwarfs as there are stars.”

In looking for the lowest-mass brown dwarfs that nature makes, Liu hopes to understand more about our own origins.

“We know that our Solar System and other systems had very dynamic early histories with a lot of jostling. It’s possible that brown dwarfs are the result of clumps of material being flung out from a proto-stellar disk. These clumps would continue condensing into massive objects but not enough to form a star.”   —  Michael Liu