WASHINGTON (AP) - Our galaxy is looking far more crowded and hospitable.
NASA on Wednesday confirmed a bonanza of 715 newly discovered planets
outside our solar system.
Scientists using the planet-hunting 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.
“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 announcements were about big numbers, they also were about
implications for life behind those big 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 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 or not too cold for liquid 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, NASA 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.
Planets in the habitable zone are likely to be farther out from their stars
because it is hot close in. And planets farther out take more time orbiting,
so Kepler has to wait longer to see it again.
Another of Kepler’s latest discoveries indicates that “small planets are
extremely common in our galaxy,” said MIT astronomer Sara Seagar, who wasn’t
part of the discovery team.
“Nature wants to make small planets.”
And, in general, smaller planets are more likely to be able to harbor life
than big ones, Kaltenegger said.