Michael Liu’s measurements of lightweight failed stars

Michael Liu: We’re finally at the point where we’re directly testing our theoretical predictions of what a very low temperature, very faint object should look like.

University of Hawaii astronomer Michael Liu is talking about his measurements of the most lightweight stellar objects found outside our solar system. They’re located about 50 light-years from Earth.

It’s a pair of brown dwarfs – sometimes called ‘failed stars’ because they lack enough mass to sustain the nuclear reactions that let stars like our sun light up.

Michael Liu: We’ve used the Keck telescope and also the Hubble Space Telescope to make very precise measurements of the orbits of brown dwarfs in binary systems.

The brown dwarfs orbit each other, and Liu measured the size and duration of their orbit to calculate their mass. But even finding them at all wasn’t easy.

Michael Liu: It’s the faintest, and it’s the coldest object, brown dwarf, which has a mass measurement. Its temperature is thousands of degrees Fahrenheit colder than the surface of the sun.

That’s about the temperature inside a pizza oven, about 800 degrees Fahrenheit.

Michael Liu: This is important because we care not only about brown dwarfs themselves, but brown dwarfs are just a stepping stone to understanding the properties of other things that we care about, namely extra-solar planets, that also can’t generate their own energy and also have very low temperature objects.

Liu added that the mass measurements of the brown dwarf pair will help test a more general class of theories in astronomy that explain how planets form around stars beyond our solar system.

Our thanks to:
Michael Liu
Institute for Astronomy
University of Hawaii
Honolulu, HI

August 10, 2008

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