An Earth-like exoplanet  (Gliese 581c) discovered 20.5 light years away.

A team of astronomers of the European Space Organization (ESO) on April 25, 2007 reported in the journal Astronomy & Astrophysics the detection of two super-Earth planets in the Gl 581 system, one of which resides in the habitable zone of the star (thus is called an exoplanet) and resembles our own Earth.

Using the ESO 3.6-m telescope at La Silla, Chile and HARPS (High Accuracy Radial Velocity for Planetary Searcher - perhaps the most precise spectrograph in the world), a team of Swiss, French and Portuguese scientists discovered a super-Earth-like planet orbiting a red dwarf [Gliese 581] and they named it Gliese 581c. The exoplanet has a radius only 50% larger than the Earth with a mass about 5 times that of Earth and completes a full orbit of the red dwarf in 13 days. It is 14 times closer to its star than the Earth is from the Sun. The exoplanet thus lies in a habitable zone, a region around a star where water could be liquid! That the new planet might be full of liquid water is at present conjecture based upon how planets form, not on any evidence. Other astronomers cautioned it's too early to tell whether there is water. "You need more work to say it's got water or it doesn't have water," said retired NASA astronomer Steve Maran, press officer for the American Astronomical Society.

Stéphane Udry, from the Geneva Observatory and lead-author said... "We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius [32 and 104 degrees F], and water would thus be liquid." "Moreover, its radius should be only 1.5 times the Earth's radius, and models predict that the planet should be either rocky - like our Earth - or fully covered with oceans."

Liquid water is critical to life as we know it and thus Gliese 581c may be important in the search for extra-terrestrial life. The planet's star, Gliese 581, is among the 100 closest stars to Earth being only 20.5 light-years away in the constellation Libra, which is low in the southeastern sky during the mid-evening in the Northern Hemisphere. Leading astronomers are describing the discovery of Gliese 581c as a big step in the search for life in the universe, because it is just the right size, might have water in liquid form, and in galactic terms is relatively nearby at 120 trillion miles away. A search for the "signatures of life" on other planets, would include the presence of oxygen in the atmosphere.

To-date astronomers have found 220 planets outside our solar system, but all have been either too hot, too cold or just plain too big and gaseous, like uninhabitable Jupiter. This new planet seems just right, or at least that's what scientists think.

What might this alien world be like: a person sitting on the planet would get heavier quickly; gravity is 1.6 times as strong as Earth's so a 150-pound person would feel like 240 pounds. Birthdays would add up fast since it orbits its star every 13 days.  Gliese 581c is 14 times closer to the star it orbits, so the red dwarf star would hang in the sky at a size 20 times larger than our moon, and the planet doesn't rotate, so one side would always be sunlit and the other dark and ice cold. The new planet's star system is a mere 20.5 light years away[20.5 x 5,879,000,000,000 statute miles]. At the speed of a NASA Space Shuttle (about 18,000 miles per hour), it would take us 6,695,528 hours [278980 days or 764.3 years) to get there.