William Atkins
Friday, 10 April 2009 20:35
Science -
Space
Page 3 of 4
When Theia collected enough material to become about the size of the planet Mars it was sent out of its L4 or L5 position by the gravitational pull of a larger planet (maybe Venus) and sent on a course that intersected Earth.
Then, whack, it hit the Earth. (A nickname for the Theia hypothesis is the Big Whack.)
As Kaiser states,
"… Theia would have been nudged out of L4 or L5 by the increasing gravity of other developing planets like Venus and sent on a collision course with Earth." [NASA]
And, the STEREO probes are entering the regions of space positioned by the L4 and L5 points. Even though Theia would no longer be there it is likely that some of the planetesimals are still there—the ones that did not coalesce with Theia—and STEREO could locate them because it can see much better than the telescopes we use on Earth for such observations.
Kaiser states,
"The STEREO probes are entering these regions of space now. This puts us in a good position to search for Theia's asteroid-sized leftovers." [NASA]
He calls them,
"Theiasteroids." [NASA]
Astronomers have searched for Theiasteroids before using ground-based telescopes, and found nothing, but
"... their results only rule out kilometer-sized objects. By actually entering L4 and L5, STEREO will be able to hunt for much smaller bodies at relatively close range." [NASA]
Page four concludes.
