A National Science Foundation artist's drawing shows the inner four planets orbiting Gliese 581, a red dwarf star just 20 light-years from Earth. The newly discovered planet, in the foreground, has a 37-day orbit and, like Earth, is distant enough from the star for liquid water to exist. Lynette Cook hide caption

itoggle caption Lynette Cook

This artist's rendering shows two Saturn-size planets discovered by NASA's Kepler telescope. Scientists say there is evidence of a third planet, a much smaller one, whose diameter appears to be about 50 percent larger than Earth's. NASA hide caption

itoggle caption NASA

Astronauts will spacewalk on Wednesday in an attempt to fix a broken cooling pump aboard the International Space Station. Though a second pump is currently working, NASA officials are worried about the possibility of it shutting down before the broken pump is fixed. NASA hide caption

itoggle caption NASA