Nearby Star Births Baby Planets

Feb. 26, 2004

WASHINGTON -- A star only 33 light-years away may be giving birth to new planets, and we are close enough to see it happen, U.S. astronomers said Thursday.

They have seen evidence of a disk of dust orbiting the star -- a disk like the one our own solar system is believed to have formed from.
And within the disk is a clear swath, which suggests a planet has started to form and has scooped up some of the dust in the process.

The star, called AU Microscopium or AU Mic, is dimmer and redder than our own sun, so any planets orbiting it are likely to be cold.

"The dust missing from the inner regions of AU Mic is the telltale sign of an orbiting planet," Michael Liu of the University of Hawaii, who helped lead the team, said in a statement.

"The planet sweeps away any dust in the inner regions, keeping the dust in the outer region at bay," Liu said.

Liu and colleagues used telescopes on Hawaii's tall Mauna Kea peak to find the young planetary system. They were pleased to find one so close.

A light-year is the distance light travels in a year, and 33 light-years is close enough to let scientists try to see the star better using the Hubble Space Telescope or ground-based telescopes.

"We know that extrasolar planets are common, but understanding how they form is an outstanding question. Because AU Mic is so near to Earth, it provides us a special opportunity to examine planet formation in great detail," Liu said.

Writing in the online Science Express version of the journal Science, Liu's team said AU Mic is extremely young -- just about 12 million years old compared to our own sun's age of 4.6 billion years.

What they see fits in with theories about how stars and planets form -- with the star forming first, and a circling ring of dust gradually accumulating into orbiting planets.

"Unfortunately, we can't go back in time and observe our own solar system. But by studying these very young stars, we can examine how planets are forming around them, and thus indirectly learn about the origin of our own solar system," Liu said.

The team looked at infrared light to get information that would be invisible to the naked eye. "When we see scattered infrared light around a star, the inference is that this is caused by dust grains replenished by comets and asteroid collisions," said Paul Kalas, an astronomer at the University of California at Berkeley who worked on the report.

"AU Mic is a common red dwarf star, which comprise 85 percent of all stars. By studying this nearby system, we might learn about how the majority of planetary systems can form," Kalas added.