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 Matt Smith, CNN
The future of NASA's planet-hunting Kepler space observatory was in question Wednesday after a part that helps aim the spacecraft stopped working, the U.S. space agency said.
Controllers found Tuesday that Kepler had gone into a "safe mode" and one of the reaction wheels needed to orient the spacecraft would not spin, Associate NASA Administrator John Grunsfeld told reporters. NASA engineers are trying to figure out whether they can get the balky part back into service or whether they can resume control by another method, Grunsfeld said.
"We're not ready to call the mission over," he said. But at roughly 40 million miles from Earth, "Kepler is not in a place where I can go up and rescue it."
The Kepler mission has identified 132 planets beyond our solar system since its launch in 2009, leading scientists to believe that most stars in our galaxy have planets circling them. It has gone into a "safe mode" with its solar panels facing back at the sun, giving controllers intermittent communication with the craft as it spins.
Is anybody out there?
For millennia, humans have gazed at the night sky, asking this question. That's why scientists and NASA are eagerly searching for "exoplanets" - that is, planets that orbit around stars other than our sun.
Last week NASA's Kepler satellite reported the discovery of three Earth-sized exoplanets within the so-called "habitable zone," defined as the neighborhood of a star where liquid water - essential for life as we know it - can exist.
By Elizabeth Landau, CNN
In the midst of chaos here on Earth, scientists are finding hope for life on other planets.
Scientists announced Thursday the discovery of three planets that are some of the best candidates so far for habitable worlds outside our own solar system - and they're very far away.
NASA's Kepler satellite, which is keeping an eye on more than 150,000 stars in hopes of identifying Earth-like planets, found the trio.
Two of the planets - Kepler-62e and Kepler-62f - are described in a study released Thursday in the journal, Science. They are part of a five-planet system in which the candidates for life are the farthest from the host star.
By Nana Karikari-apau, CNN
Editor's note: The Science Seat is a feature in which CNN Light Years sits down with movers and shakers from different areas of scientific exploration. This is the seventh installment.
Sara Seager is a professor of physics and planetary science at MIT. She works on exoplanets, which orbit stars other than the sun.
Seager considers herself a pioneer and risk taker. She worked on exoplanets before it was considered cool, when people thought the field would go nowhere. Time magazine named Seager one of the 25 most influential in space in 2012, and she recently appeared in a CNN gallery of top women scientists.
MIT's Sara Seager studies exoplanets, which orbit stars other than the sun.
CNN Light Years recently chatted with Seager about her work. Here is an edited transcript:
By Matt Smith, CNN
It's not the kind of place you'd call home: an airless, rocky planet so close to its sun that some metals will melt on its surface.
But it's a big little discovery for NASA's space observatory Kepler. The space agency says the planet, dubbed Kepler-37b, is the smallest yet found beyond our solar system.
Slightly larger than the moon and about a third the size of Earth, it's one of three planets circling the star Kepler-37, NASA announced Wednesday - and the first of dozens of discovered exoplanets known to be smaller than any that orbit our sun.
The findings were reported in this week's edition of the journal Nature.
By Elizabeth Landau, CNN
We still don't know if Earth, as a planet that currently harbors life, is alone in the universe. But scientists are actively searching for clues about other potential habitable worlds outside our solar system.
Astronomers are presenting their latest findings at the American Astronomical Society annual conference in Long Beach, California, this week. The word on the cosmic street is that Earth-sized planets are relatively common and that hundreds of new planet candidates have been identified.
"We have begun to truly map the planets in our galaxy akin to the way that early explorers mapped the Earth," said Sara Seager, professor of planetary science and physics at the Massachusetts Institute of Technology, who works with data from the NASA Kepler mission, which aims to identify planets outside of Earth's solar system.
By Zaina Adamu, CNN
Could there be extraterrestrial life in our own Milky Way galaxy?
NASA’s Kepler mission, using an orbiting telescope equipped with a 95-megapixel camera and 42 charge-coupled devices, discovered that worlds, one-half to twice the size of Earth, exist in our galaxy.
Kepler is the first mission with the potential to identify Earth-sized planets that exist near the habitable zones of their stars, a landmark in astronomy because the finding could lead scientists to discover that, indeed, life exists in other places besides Earth.
The way Kepler detects planets is similar to how we detect Venus and Mercury from Earth. Every so often, there are events where Venus and Mercury pass the sun, briefly blocking a bit of the sunlight coming to Earth. From our perspective, each of these events, called a transit, is seen as a slow-moving black speck traveling across the sun.
Thirty-five years ago, a scene in the first "Star Wars" film captivated movie-goers: Luke Skywalker peering across the landscape of Tatooine - a desert planet dominated by a pair of setting suns.
This week, reality trumped (science) fiction with an image even more enthralling: two amateur astronomers poring through data from deep, distant skies and discovering a planet with four suns.
NASA's website calls the phenomenon a circumbinary planet, or a planet that orbits two suns.
The discovery of a planetary "odd couple" is broadening the way scientists think about planetary migration.
Scientists at the Harvard Smithsonian Center for Astrophysics and University of Washington discovered two planets of very different sizes and makeups orbiting Kepler-36, a sun-like star under nearly continuous surveillance by the Kepler spacecraft.
"This is kind of an extreme system in that the planets are relatively closely spaced in their orbits but their compositions are quite disparate," said Josh Carter, Hubble Fellow at the Harvard Smithsonian Center for Astrophysics who discovered the smaller planet.
"They're quite the odd couple."