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NASA announces ‘mother lode’ of new planets: 715

An artist conception of the Milky Way galaxy, which has about 1,700 confirmed planets.

AP Photo/NASA

An artist conception of the Milky Way galaxy, which has about 1,700 confirmed planets.

WASHINGTON — Our galaxy is looking far more crowded and hospitable. NASA on Wednesday confirmed a bonanza of 715 newly discovered planets.

Scientists using the Kepler telescope pushed the number of planets discovered in the galaxy to about 1,700. Twenty years ago, astronomers had not found any planets circling stars other than the ones revolving around our sun.

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‘‘We almost doubled just today the number of planets known to humanity,’’ NASA planetary scientist Jack Lissauer said in a Wednesday teleconference, calling it ‘‘the big mother lode.’’

Astronomers used a new confirmation technique to come up with the largest single announcement of a batch of exoplanets — what planets outside our solar system are called.

While Wednesday’s announcement was about big numbers, it also was about implications for life behind those numbers.

All the new planets are in systems like ours where multiple planets circle a star. The 715 planets came from looking at just 305 stars. They were nearly all in a size closer to Earth than gigantic Jupiter.

And four of those new exoplanets orbit their stars in ‘‘habitable zones’’ where it is not too hot nor too cold for water, which is crucial for life to exist.

Douglas Hudgins, NASA’s exoplanet exploration program scientist, called Wednesday’s announcement a major step toward Kepler’s ultimate goal: ‘‘finding Earth 2.0.’’

It’s a big step in not just finding other Earths, but ‘‘the possibility of life elsewhere,’’ said Lisa Kaltenegger, a Harvard and Max Planck Institute astronomer who wasn’t part of the discovery team.

The four new habitable zone planets are all at least twice as big as Earth, so that makes them more likely to be gas planets instead of rocky ones like Earth — and less likely to harbor life.

So far Kepler has found nine exoplanets in the habitable zone, the National Aeronautics and Space Administration said. Astronomers expect to find more when they look at all four years of data collected by the now-crippled Kepler; so far they have looked at two years.

Another of Kepler’s latest discoveries indicates that ‘‘small planets are extremely common in our galaxy,’’ said Massachusetts Institute of Technology astronomer Sara Seagar, who wasn’t part of the discovery team. ‘‘Nature wants to make small planets.’’

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