An artist's illustration of an Earth-like planet. The search for planets that are similar to Earth is one of NASA's main goals. Many planets have already been discovered orbiting other stars, but so far only larger planets (the size of Jupiter or larger) have been found. New missions are being planned by NASA which will be able to detect smaller Earth-sized planets. Some of these missions will also try to detect signs of life on these planets by studying emissions in their atmospheres.


Many "Earths" Are Out There, Study Says

SOURCE: National Geographic News
Brian Handwerk
April 6, 2005

A new study of known planetary systems outside our solar system gives a theoretical boost to the search for extraterrestrial life. Researchers in England say that half of the systems could harbor habitable, Earthlike planets.

Barrie Jones, an astronomer at the Open University in Milton Keynes, England, co-authored the new study. He said, "We were particularly interested in the possible survival of 'Earths' in the habitable zone."

"This is often called the Goldilocks zone—where the temperature of an 'Earth' is just right for water to be liquid at its surface. If liquid water can exist, so could life as we know it."

The location of a system's habitable zone depends on how bright and hot the that system's star is. The zone can shift over the eons as the star ages and becomes brighter and hotter.

Jones collaborated with Open University colleagues Nick Sleep and David Underwood. The team used computer models to map the habitable zone in some 130 known exoplanetary systems—star-planet formations found outside our solar system.

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