Reference no: EM133319387

Alien Planets

They're out there in the depths of space. There are giant ones, small ones, weird ones, and most likely ones we can't even imagine. We're talking about planets, of course. For years, astronomers have speculated that the sun is not the only star with planets circling it. Now, thanks to the Kepler space telescope, they have proof that our Milky Way galaxy could actually be teeming with planets of all sizes and types.

The Kepler space telescope, which orbits the sun between Earth and Mars, is the most advanced and sensitive optical telescope ever constructed. It was launched on March 7, 2009 and is named after Johannes Kepler, the 16th-century German astronomer who discovered the laws of planetary motion. It is so light sensitive that, if it were pointed back toward Earth at night, it would be able to detect when one person in a small town turned off a single porch light.

Kepler's mission, however, is not to detect porch lights. The spacecraft has one mission only-exoplanet hunting, planets that orbit stars other than our sun. For nearly two years, it has been peering at approximately 100,000 stars in a portion of the Milky Way. On February 2, NASA, the U.S. space agency, released its findings from Kepler's sky search conducted between May and September 2009. The telescope had discovered 1,235 possible exoplanets orbiting 997 stars. The find includes 68 about the size of Earth and 54 planets in what scientists call the Goldilocks zone-the zone around a star that permits liquid surface water, considered an essential condition to produce life.

As sensitive as it is, Kepler cannot see the planets themselves, and instead, uses what scientists call the transit technique. The stars it is looking at are from a few hundred to a few thousand light-years away. A light-year is the distance that light, traveling at 186,000 miles per second, covers in a year. That distance comes to approximately 5.9 trillion miles. The telescope is able to measure the very slight drop in starlight that occurs when an orbiting object passes in front of a star. Once Kepler registers an object passing around a star (usually after three passes), teams of scientists on Earth begin to focus on the object and try to analyze it in order to verify that it is really an exoplanet. It takes a lot of time and work, which is why it has taken two years to confirm many of Kepler's discoveries.

Many astronomers think that it is only a matter of time before Kepler locates Earth's twin revolving around a star that may even be close to us. The space telescope has surveyed only a tiny fraction of the stars in the Milky Way. Once an Earth-like exoplanet is discovered, however, finding out whether it has all the ingredients for life will be a new hurdle. It will require costly new telescopes, including one capable of scanning such planets for evidence of oxygen, water, and carbon dioxide. Such a huge scientific mission will be expensive, but many scientists believe the exploration should continue at any cost. "We are at a very special moment in the history of mankind," Cornell University astronomer Martha Haynes told The Associated Press.

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