Narrator: This is Science Today. Planets discovered outside our solar system were found to have an elliptical orbit, rather than the circular orbit of our own planets. Geoff Marcy, a professor of astronomy at the University of California, Berkeley, says this makes astronomers wonder if circular orbits are necessary for the evolution of advanced life.

Marcy: If instead, the Earth were residing in an elliptical orbit, then of course the Earth would get carried close to the sun and far from the sun and close to sun, alternately heating up the water to steam and the other half of the time, freezing the water on the Earth into ice. And of course, that would not bode well for the quiescent evolution of microbiology and life in general.

Narrator: Marcy says their results are a bit scary for researchers looking for extra-terrestrial life.

Marcy: But I try to assure them they should not be scared - only five percent of the stars we've looked at have Jupiters. And although those Jupiters are in elliptical motion, the other ninety-five percent of our stars could very well have Earth-like planets in circular motion.

Narrator: For Science Today, I'm Larissa Branin.