Has a Massive Collision in the Pleiades Been Creating Earthlike Planets?

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Rocky terrestrial planets, perhaps like Earth, or Venus, appear to be forming or to have recently formed around a star in the Pleiades star cluster, astronomers using the Gemini Observatory in Hawaii and the Spitzer Space Telescope have observed. The planets appear to be  the result of "monster collisions" of planets or planetary embryos.


Famous as the Seven Sisters or Subaru, in Japan, The Pleiades is the name of an open cluster in the constellation of Taurus dominated by hot blue stars, which have formed within the last 100 million years. It is among the nearest to the Earth of all open clusters, probably the best known and certainly the most obvious to the naked eye.

The Pleiades have been considered important by many cultures throughout history. In Bronze Age Europe, the Celts and others associated the Pleiades with mourning and funerals because the cluster rose in the eastern night sky between the autumnal equinox and the winter solstice, which was a festival devoted to the remembrance of the dead. The ancient Aztecs of Mexico and Central America based their calendar on the Pleiades.

Two astronomers, using the Gemini Observatory in Hawaii and the Spitzer Space Telescope, found evidence of past and possibly future rocky planets, similar to our own first four planets. One of the clusters stars — HD 23514 €“ has been found to be surrounded by a large amount of hot dust particles.

"Hundreds of thousands of times as much dust as around our sun," said research co-author Benjamin Zuckerman, UCLA professor of physics and astronomy. "The dust must be the debris from a monster collision, a cosmic catastrophe."

Co-author Inseok Song, a staff scientist at NASA's Spitzer Science Center at the California Institute of Technology and a former astronomer with the Gemini Observatory, calls the dust particles observed the "building blocks of planets. These building blocks can eventually form asteroids, comets, and later on, clump together to form planetary embryos or planets.

It is the same process which is believed to have formed our own moon. Believed to be a creation of a cataclysmic encounter between a young Earth and a sized planet, occasionally called Orpheus or Theia, our moon is thought to have coalesced from the remains of that collision.

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

A young sun will often be surrounded by dust. The age though of HD 23514, a hundred million years old, is too old for that primordial dust to still be around. This is another proof for the researchers to suggest that it is a recent collision between rocky bodies.

This team were the same responsible for the 2005 discovery of similar dust particles orbiting the star BD +20 307, in the Aries constellation. It was their efforts to continue their research that led them to find images taken by the Spitzer Space Telescope of HD 23514.

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

The Daily Galaxy via space.com and physorg.com

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