Narrator: This is Science Today. For the first time, astronomers have witnessed a distant planet passing in front of its star. Geoff Marcy, a professor of astronomy at the University of California, Berkeley, says this is the first direct confirmation of their existence.

Marcy: What we have found now, is a planet that just be luck, crosses in front of the star and in so doing, the planet actually blocks some of the light that normally would come to us from the star and because of that blocking of light, the star dims. And you can see this in a telescope.

Narrator: Marcy and his colleagues were then able to discover this planet's mass is smaller than our own Jupiter, but its diameter is much larger.

Marcy: It's amazing, but the theoretical astrophysicists had predicted that planets close to their host stars should be puffed out - bloated out by the heat generated by the star hitting the planet. And sure enough, this planet is indeed is bigger. This shows that in fact their theories are right and perhaps they really do understand the interiors and the atmospheres of as yet, unseen planets.

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