Small planets forming in the Pleiades: astronomers


Nov 14, 2007

WASHINGTON (Reuters) - Small, rocky planets that could resemble the Earth or Mars may be forming around a star in the Pleiades star cluster, astronomers reported on Wednesday.

One of the stars in the cluster, also known as the Seven Sisters, is surrounded by an extraordinary number of hot dust particles that could be the "building blocks of planets" said Inseok Song, a staff scientist at NASA's Spitzer Science Center at the California Institute of Technology.

"This is the first clear evidence for planet formation in the Pleiades, and the results we are presenting may well be the first observational evidence that terrestrial planets like those in our solar system are quite common," said Joseph Rhee of the University of California Los Angeles, who led the study.

There is "hundreds of thousands of times as much dust as around our sun," said Benjamin Zuckerman, a UCLA professor of physics and astronomy. "The dust must be the debris from a monster collision, a cosmic catastrophe."

The team used two telescopes to spot the dust, and report their findings in Astrophysical Journal.

Located about 400 light years away in the constellation of Taurus, the Pleiades is one of the best known star clusters and among the closest to Earth. A light-year is the distance light travels in a year, about 5.8 trillion miles.

"The cluster actually contains some 1,400 stars," said Song.

Song said the dust can accumulate into comets and small asteroid-size bodies, and then clump together to form planetary embryos, and finally full-fledged planets.

"In the process of creating rocky, terrestrial planets, some objects collide and grow into planets, while others shatter into dust; we are seeing that dust," Song said.

"Our observations indicate that terrestrial planets similar to those in our solar system are probably quite common," Zuckerman added.

Researchers have observed about 200 planets around stars outside our solar system but none are as small as Earth and just one, spotted earlier this year, appears potentially capable of supporting life.