Published on March 8, 2009

Are we Alone in Space?

NASA's Kepler Mission Rockets to Space in Search of Other Earths

CAPE CANAVERAL, Fla. -- NASA's Kepler mission successfully launched into space from Cape Canaveral Air Force Station, Fla., aboard a United Launch Alliance Delta II at 10:49 p.m. EST, Friday, March 6, 2009

Kepler in space (artist concept). Image credit: NASA/JPL

Five Things About Kepler

• Kepler is the world's first mission with the ability to find true Earth analogs -- planets that orbit stars like our sun in the "habitable zone." The habitable zone is the region around a star where the temperature is just right for water - an essential ingredient for life as we know it - to pool on a planet's surface.

• By the end of Kepler's three-and-one-half-year mission, it will give us a good idea of how common or rare other Earths are in our Milky Way galaxy. This will be an important step in answering the age-old question: Are we alone?

• Kepler detects planets by looking for periodic dips in the brightness of stars. Some planets pass in front of their stars as seen from our point of view on Earth; when they do, they cause their stars to dim slightly, an event Kepler can see.

• Kepler has the largest camera ever launched into space, a 95-megapixel array of charge-coupled devices, or CCDs, like those in everyday digital cameras.

• Kepler's telescope is so powerful that, from its view up in space, it could detect one person in a small town turning off a porch light at night.

Kepler is designed to find the first Earth-size planets orbiting stars at distances where water could pool on the planet's surface. Liquid water is believed to be essential for the formation of life.

"It was a stunning launch," said Kepler Project Manager James Fanson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Our team is thrilled to be a part of something so meaningful to the human race -- Kepler will help us understand if our Earth is unique or if others like it are out there."

Engineers acquired a signal from Kepler at 12:11 a.m. Saturday, after it separated from its spent third-stage rocket and entered its final sun-centered orbit, trailing 950 miles behind Earth. The spacecraft is generating its own power from its solar panels.

"Kepler now has the perfect place to watch more than 100,000 stars for signs of planets," said William Borucki, the mission's science principal investigator at NASA's Ames Research Center at Moffett Field, Calif. Borucki has worked on the mission for 17 years. "Everyone is very excited as our dream becomes a reality. We are on the verge of learning if other Earths are ubiquitous in the galaxy."

Engineers have begun to check Kepler to ensure it is working properly, a process called "commissioning" that will take about 60 days. In about a month or less, NASA will send up commands for Kepler to eject its dust cover and make its first measurements. After another month of calibrating Kepler's single instrument, a wide-field charge-couple device camera, the telescope will begin to search for planets.

The first planets to roll out on the Kepler "assembly line" are expected to be the portly "hot Jupiters" - gas giants that circle close and fast around their stars. NASA's Hubble and Spitzer space telescopes will be able to follow up with these planets and learn more about their atmospheres. Neptune-size planets will most likely be found next, followed by rocky ones as small as Earth. The true Earth analogs - Earth-sized planets orbiting stars like our sun at distances where surface water, and possibly life, could exist - would take at least three years to discover and confirm. Ground-based telescopes also will contribute to the mission by verifying some of the finds.

In the end, Kepler will give us our first look at the frequency of Earth-size planets in our Milky Way galaxy, as well as the frequency of Earth-size planets that could theoretically be habitable.

"Even if we find no planets like Earth, that by itself would be profound. It would indicate that we are probably alone in the galaxy," said Borucki.

As the mission progresses, Kepler will drift farther and farther behind Earth in its orbit around the sun. NASA's Spitzer Space Telescope, which was launched into the same orbit more than five years ago, is now more than 62 million miles behind Earth.