During the first hour, astronomer Phil Plait(1) discussed the discoveries of two new "planets" in our outer solar system. One, he said, is believed to be larger than Pluto, the other, though smaller, has its own moon. For more on this, see this special page(2) that he's prepared.
Then, Richard C. Hoagland(3) joined the show, commenting that the recent planetary discoveries were fostered by a competition between two scientific teams, Caltech and a group in Spain. He also shared an update on the Shuttle, suggesting that the problem with the foam/tiles dates back to missions from 1997.