Older Stars Forming New Planets

via ScienceDaily, astronomers have discovered two odd stellar system in which new planets are forming around two different stars that actually quite old.

""This is a new class of stars, ones that display conditions now ripe for formation of a second generation of planets, long, long after the stars themselves formed," said UCLA astronomy graduate student Carl Melis, who reported the findings today at the American Astronomical Society meeting in Austin, Texas.

"If we took a rocket to one of these stars and discovered there were two totally distinct ages for their planets and more minor bodies like asteroids, that would blow scientists' minds away," said Benjamin Zuckerman, UCLA professor of physics and astronomy and co-author of the research, which has not yet been published. "We're seeing stars with characteristics that have never been seen before."

The stars are BP Piscium, 200 light years form Earth in the constellation Pisces, and TYCHO 4144 329 2, in the constellation Ursa Major. Both stars have the standard cloud of dust and gas surrounding them, a characteristic of young stars, which form small stellar bodies called planetesimals, which later tend to clump together to form planets. They also exhibit high infared light emissions like many younger stars. However, in the case of these two stars, things did not add up, as both stars spectroscopic analysis showed much smaller amounts of the element lithium (which stars burn up as they age) than should be the case for a relatively young star. The lithium signature for BP Piscium is seven times less than a normal young star of similar mass. Other spectral measurements also indicate these stars are much older than they initially appeared as well. Conversely, their infared emissions are also at an unusually high level for a mature star.

Both the Hubble Space Telescope and the Chandra X-Ray Observatory have been making and will continue to make observations of the two systems along with other Earth based telescopes, and astronomers are seeking other examples of older stars exhibiting the same characteristics.