NASA today announced the discovery of 715 planets orbiting 305 stars, revealing multi-planet systems much like our own solar system.

Four of these newly verified planets are in their sun's habitable zone, a distance from a star where the temperature is conducive to the planet's having water in liquid form. With water, it's possible these four planets could potentially hold life.

"This is the largest windfall of planets that's ever been announced at one time," said Douglas Hudgins, NASA's exoplanet exploration program scientist. "Planetary systems, with planets orbiting a star like our own, are in fact common. There are an abundance of habitable Earth-sized planets. Our goal is to find Earth 2.0 -- an Earth-like planet that could hold life."

NASA released this artist rendering of multi-planet systems, which are stars with more than one planet. The space agency said scientists have verified 715 exoplanets. (Image: NASA)

Echoing the scientists around him during a press conference, Hudgins added, "These are really exciting times."

Prior to this discovery, scientists knew about 1,000 exoplanets, which are planets outside our own solar system.

The 715 planets were spotted and verified by NASA's Kepler Space Telescope, which began its work on May 12, 2009.

The discoveries came from the first two years of data that Kepler sent back to Earth. Scientists said they are now beginning to study the data from the second two years of Kepler's planet-hunting mission and expect to find hundreds of other planets.

This is all good news for Kepler, which last summer was forced to end its primary mission of finding planets outside this solar system that are capable of supporting life.

The space telescope had two broken wheels that caused it to spin out of control. It could not be repaired well enough to return it to its initial work.

Scientists received enough data from Kepler to determine not only the size of a planet but whether it has a solid surface and its potential to have water in liquid form, which is considered crucial to the formation of life.

While the space telescope was still working, it observed 150,000 stars and hundreds that potentially are orbited by multiple planets. Through a careful study of this sample, scientists verified the 715 new planets.

According to NASA, nearly 95% of these planets are smaller than Neptune, which is almost four times the size of Earth. All of them are in multi-planet systems and have flat and circular orbits -- much like our own solar system, placing our outer-space neighborhood in context.

The discovery marks a significant increase in the number of known smaller planets that are more similar to Earth than previously identified exoplanets.

"We've been able to open the bottleneck and access the mother lode and announce more than 20 times as many planets as has ever been found at one time," said Jack Lissauer, a planetary scientist with NASA. "It's a veritable exoplanet bonanza."

Sara Seager, a professor of physics and planetary science at MIT, said Kepler has revolutionized the study of exoplanets. "Kepler is the gift that keeps on giving," she said.

Scientists said Kepler's discoveries will be advanced when the James Webb Space Telescope, which the space agency calls the next great observatory, is launched in 2018.

The new space telescope is geared to be the successor to the Hubble Space Telescope, and will search for the first galaxies that formed in the early universe and hopefully givie scientists information about the Big Bang and the Milky Way. It also should shine new light on these hundreds of exoplanets.

This article, Hunting for Earth 2.0: NASA finds 715 new planets, was originally published at Computerworld.com.

Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at @sgaudin, on Google+ or subscribe to Sharon's RSS feed . Her email address is sgaudin@computerworld.com.

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