2nd largest asteroid in Solar System identified as protoplanet

The second largest asteroid in the Solar System is actually a protoplanet, a building block to the actual, larger planets, a new study suggests.

Researchers at the University of California in Los Angeles (UCLA) drew the conclusion after using the Hubble Space telescope to view Pallas, the second largest asteroid in the Solar System, according to the study appearing in the October issue of Science.

Pallas, which is named for the Greek goddess Pallas Athena, lies in the main asteroid belt between the orbits of Jupiter and Mars.

According to the planet formation theory, protoplanets are a cloud of gas, rocks and dust particles that are in the process of forming into a planet. Protoplanets get in the way of each other's orbits slightly, collide with the impacts gradually forming a real planet.

"It was incredibly exciting to have this new perspective on an object that is really interesting and hadn't been observed by Hubble at high resolution," said UCLA doctoral student Britney E. Schmidt, the study's lead author.

"We think of these large asteroids not only as the building blocks of planets but as a chance to look at planet formation frozen in time."

"To have the chance to use Hubble at all, and to see those images come back and understand automatically this could change what we think about this object -- that was incredibly exciting tome," Schmidt said.

Images from the Hubble Space Telescope suggest that the asteroid Pallas should be grouped along with two other big space rocks as protoplanets - "planetary embryos" that were big enough to stay pretty much as they were during the formation of the solar system, but too small to progress to the next stage of development.

Schmidt said she and her colleagues were able to make new measurements of Pallas' size and shape. They were able to see that its surface has areas of dark and light, indicating that the water-rich body might have undergone an internal change in the same way planets do.

"That's what makes it more like a planet - the color variation and the round shape are very important as far as understanding, is this a dynamic object or has it been exactly the same since it's been formed," Schmidt said. "We think it's probably a dynamic object."

For the first time, Schmidt said she and her colleagues also saw a large impact site on Pallas. They were unable to determine if it was a crater, but the depression did suggest something else important: that it could have led to Pallas' small family of asteroids orbiting in space.

A Sci-Tech news from Xinhua



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