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Fifth Planet

May 2, 2006

Last year astronomers found what some are calling a tenth planet. But new research shows that the real tenth planet may have come and gone years ago.


Earth’s missing sister. I’m Bob Hirshon and this is Science Update.

Another planet may have once inhabited the area of our solar system between Mars and Jupiter. This according to astronomer Sean Raymond of the University of Colorado at Boulder. He’s named the planet Artemis, and his simulations show that it would have formed along with Earth at double the Earth’s distance to the Sun. But about 4 billion years ago, the giant outer planets shifted their orbits, and that was trouble for the much smaller Artemis.

SEAN RAYMOND (University of Colorado at Boulder):
It’s orbit would have become unstable. There’s a chance it would have fallen into the sun, but it’s probably a little more likely that it would have had a close encounter with Jupiter and gotten gravitationally scattered and ejected from the solar system.

Earth, on the other hand, moved to its current orbit. Raymond hopes to find evidence of Artemis among the solar system’s asteroids. I’m Bob Hirshon, for AAAS, the science society.