Launching Kepler

Next Friday NASA is scheduled to launch a satellite known as "Kepler", on a several year mission to find planets like the Earth around distant stars like the Sun. As a member of the committee that leads an international collaboration of astronomers who will be analyzing some of the data from this mission, I received an invitation from NASA to attend the launch in person.

Kepler is an enormous science-grade digital camera with nearly 95 megapixels (compare that to your digital camera at home). The giant camera is attached to a telescope with a mirror more than 55 inches across, which will stare at a large patch of the sky just above the Milky Way for at least the next few years. The diameter of each image on the sky will be as wide as 24 full moons lined up side by side, and the camera will normally take 30-minute long exposures. The images will be processed on board the spacecraft to measure the brightness of more than 100,000 stars, and these measurements will be saved and transmitted to the Earth every few months.

Some fraction of the stars that Kepler monitors will have planets, and some fraction of those planetary systems will be oriented in such a way that the alien worlds pass directly in front of their host star from the vantage point of the telescope. It's sort of like an eclipse, except the planet will only cover a small fraction of the surface of the star for up to a few hours, causing a small dip in the amount of light recorded by Kepler's camera. Astronomers are particularly interested in finding planets similar to the Earth, which are far enough from their stars that water exists in liquid form, but not so far that the water becomes mostly frozen. Like the Earth, such planets will go around their stars only about once a year -- so scientists will be looking for stars that show several tiny dips in light, each separated by about a year. By looking at more than 100,000 stars, Kepler should be able to find at least a few planets like the Earth if they are at all common. If not, that will also be a very interesting thing to know!

The satellite will be launched on a Delta II rocket next Friday evening from Cape Canaveral, Florida. The Delta II is the same vehicle used by NASA to put GPS satellites into orbit, and night launches are particularly spectacular since you can easily see the rocket ascend all the way to the edge of the Earth's atmosphere. Kepler will be placed in orbit around the Sun, just behind the Earth, and will slowly drift further away over the next few years. By then its mission should be finished, and we will know exactly how special the Earth really is -- or how common it is to find planets just like ours in the neighborhood.

Although I'm not part of the official science team, I've been preparing for the Kepler mission for the past several years. I just got a grant from NASA to continue this work for the next few years. Cross your fingers that everything goes well!