Editor's note: Meg Urry is the Israel Munson professor of physics and astronomy and chairwoman of the department of physics at Yale University, where she is the director of the Yale Center for Astronomy and Astrophysics.
(CNN) – On Wednesday, NASA officials announced a serious problem with the Kepler satellite, the world's most successful planet-finding machine.
Since its launch four years ago, Kepler has found more than 2,700 possible planets orbiting stars other than our Sun, of which more than 100 have been confirmed. A few of these exoplanets resemble the Earth in size or mass.
Recently, three Earth-like planets were even reported to be in the habitable zone: close enough to the star they orbit that water is liquid, yet not so close that it is boiling. Planets with liquid water may well harbor life.
By Jason Moon, CNN
A meteoroid struck the surface of the moon recently, causing an explosion that was visible on Earth without the aid of a telescope, NASA reported Friday. But don't be alarmed if you didn't see it; it only lasted about a second.
"It exploded in a flash nearly 10 times as bright as anything we've ever seen before," said Bill Cooke, of NASA's Meteoroid Environment Office.
NASA astronomers have been monitoring the moon for the past eight years, looking for explosions caused by meteoroids hitting the lunar surface. It's part of a program to find new fields of space debris that could hit Earth. NASA says it sees hundreds of detectable lunar meteoroid impacts a year.