PhysBrain says:

I’m not an astronomer, but I can tell you what I know about Kepler.

I remember first hearing about Kepler back in 1997 at NASA Ames when it was still on the drawing board. Back when there was only about a dozen known exo-planets, all of which had been detected by the wobble method (wherein one looks at the way a star wobbles in space and thereby deduces that there is a massive body in orbit pulling it this way and that). At that time, no one believed that a ground based telescope could make an exo-planet discovery by the transit method because a) the atmosphere would make it almost impossible to get a precise measurement of the magnitude (brightness) of the star, and b) no one would be able to get enough time on one of the large telescopes to stare at a star unless one knew in advance when and where a transit would occur. Placing a telescope in orbit and dedicating it to staring at a specific patch of sky seemed like the best way to overcome both of these obstacles. Also, the wobble method is best suited to discovering rather large planets (Neptune sized and larger). The transit method is much more sensitive, and could theoretically detect planets a small as the Earth.

The transit method used by Kepler watches for signs of exo-planets momentarily passing in front of their star. At least three important things may be deduced by observing such a transit. First, the size of the planet may be accurately determined from the amount of star light which is blocked by planet as it transits. Second, based on the length of the transit, they can figure out some of the orbital parameters, such as how far away from the star the planet is orbiting, and what is it’s period. Third, the spectrum of the star light may be observed to look for tell-tale signs of certain molecules in the planet’s atmosphere. The latter is probably not going to be done by Kepler. A more powerful telescope will most likely do more detailed observations once the expected transit times are worked out from the Kepler data.

Now, if I may make a suggestion about the podcast. You guys are fun to listen to, and all that, but could you please try to do a little research on the topic of the day before hitting the air? At the very least, consider doing two takes. If you find yourself rambling, or at a loss in the first take, then you have the opportunity to pull yourself together and actually impart some useful information in the second take. It may not seem as spontaneous the second time through, but I’ll bet you can make it work.

Good luck.