Friday, 27 May 2011

Space telescope Spitzer observes crystal "rain" in outer clouds of infant star

NASA's Spitzer Space Telescope detected tiny green crystals, called olivine, thought to be raining down on a developing star. This graphic illustrates the process, beginning with a picture of the star and ending with an artist's concept of what the crystal "rain" might look like. (Photo: NASA.com)

LOS ANGELES, May 26 (Xinhua) -- NASA's space telescope Spitzer have observed olivine falling down like rain on a burgeoning star, it was announced on Thursday.

This is the first time such crystals have been observed in the dusty clouds of gas that collapse around forming stars, according to NASA's Jet Propulsion Laboratory (JPL).

Spitzer's infrared detectors spotted the crystal rain around a distant, sun-like embryonic star, or protostar, referred to as HOPS-68, in the constellation Orion, said JPL in Pasadena, Los Angeles.

In the form of forsterite, the crystals belong to the olivine family of silicate minerals and can be found everywhere from a periodot gemstone to the green sand beaches of Hawaii to remote galaxies, JPL said.

NASA's Stardust and Deep Impact missions both detected the crystals in their close-up studies of comets.

Astronomers are still debating how the crystals got there, but the most likely culprits are jets of gas blasting away from the embryonic star.

"You need temperatures as hot as lava to make these crystals," said Tom Megeath of the University of Toledo in Ohio, the principal investigator of the research and the second author of a new study appearing in Astrophysical Journal Letters. "We propose that the crystals were cooked up near the surface of the forming star, then carried up into the surrounding cloud where temperatures are much colder, and ultimately fell down again like glitter."

"If you could somehow transport yourself inside this protostar' s collapsing gas cloud, it would be very dark," said Charles Poteet, lead author of the new study, also from the University of Toledo. "But the tiny crystals might catch whatever light is present, resulting in a green sparkle against a black, dusty backdrop."

Forsterite crystals were spotted before in the swirling, planet- forming disks that surround young stars.

The discovery of the crystals in the outer collapsing cloud of a proto-star is surprising because of the cloud's colder temperatures, about minus 280 degrees Fahrenheit (minus 170 degrees Celsius), said JPL.

This led the team of astronomers to speculate the jets may in fact be transporting the cooked-up crystals to the chilly outer cloud.

The findings might also explain why comets, which form in the frigid outskirts of the solar system, contain the same type of crystals, said JPL.

Comets are born in regions where water is frozen, much colder than the searing temperatures needed to form the crystals, approximately 1,300 degrees Fahrenheit (700 degrees Celsius). The leading theory on how comets acquired the crystals is that materials in young solar system mingled together in a planet- forming disk. In this scenario, materials that formed near the sun, such as the crystals, eventually migrated out to the outer, cooler regions of the solar system.

Poteet and his colleagues say this scenario could still be true but speculate that jets might have lifted crystals into the collapsing cloud of gas surrounding our early sun before raining onto the outer regions of the forming solar system.

Eventually, the crystals would have been frozen into comets, the scientists say.