Kepler II 
A NASA spacecraft known as Kepler has discovered more than a dozen confirmed planets in other star systems. But the work is just beginning. Kepler itself has more than a year remaining in its main mission. And astronomers are using ground-based telescopes to make sure that a long list of possible planets really are what they seem to be. Bill Cochran is an astronomer at the University of Texas and a member of the Kepler team:
COCHRAN: In February of 2011 we released a list of about 1255 possible planet candidates. So the team is really hard at work in confirming a large number of additional planets.
Kepler looks for a star's light to dim by a tiny bit as a possible planet passes in front of it. Many of those flickers really are produced by orbiting planets. But others are the result of another star or some other source of interference.
So astronomers are using several telescopes -- including two at McDonald Observatory -- to try to confirm that Kepler really has seen a planet and not something else.
COCHRAN: So we go to the observatory out in West Texas, McDonald Observatory, and we use the 2.7-meter telescope there and we make measurements of the velocities of the stars at different points in the orbit of whatever object it is around the star. If the orbiting object is another star we'll see a large velocity signal, if the orbiting body is a planet, then we'll see a very small signal.... The stars are faint, so it's a very difficult measurement.
Script by Damond Benningfield, Copyright 2011