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Thousands of planets have been detected around faraway stars in recent years. And now scientists studying those planets may have found the first moon. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE, BYLINE: Even in our own solar system, some of the most intriguing places to hunt for life are moons, like Enceladus and Europa around Saturn and Jupiter. These moons seem to have oceans of water beneath an icy crust. It's been hard enough to find planets around distant stars, let alone moons. Still, David Kipping thinks he's finally found really good evidence for one.
DAVID KIPPING: The fact is it's so strange, and it's the first of its kind. That demands a higher level of rigor and skepticism than you would normally apply to a run-of-the-mill detection.
GREENFIELDBOYCE: Kipping is an astronomer at Columbia University. He points out that our moon - the one with the astronaut footprints - isn't just a pretty face. It keeps our planet's tilt stable. It affects the tides.
KIPPING: So when we look for an Earth twin, I think one of the most obvious things you might ask is, does it have a moon twin, because that seems to have a large influence.
GREENFIELDBOYCE: What's more - he wants to find moons because when E.T. calls home, there's no reason home couldn't be a moon.
KIPPING: That's been a key driver for us for a while, just trying to understand the cosmic habitats out there that we might look for for life.
GREENFIELDBOYCE: A couple years ago, he and a colleague named Alex Teachey began scrutinizing data collected by NASA's Kepler space telescope. They checked around 300 planets for any weirdness that might mean a moon. What popped out was a planet called Kepler-1625b, a Jupiter-sized world that orbits a star around 8,000 light-years away.
They followed up with the Hubble Space Telescope. And today, in the journal Science Advances, they say this gas giant appears to have a Neptune-sized moon.
KIPPING: We're still not 100 percent sure about that, but we think it's the leading hypothesis.
GREENFIELDBOYCE: The researchers have requested more time on Hubble to do more observations next May.
MEGAN BEDELL: If this does pan out and turn into a true discovery, it would be really revolutionary.
GREENFIELDBOYCE: Megan Bedell is an astronomer at the Flatiron Institute in New York. She says moons are kind of the next frontier when it comes to understanding alien solar systems.
BEDELL: They capture imagination.
GREENFIELDBOYCE: She says if this moon can't be confirmed, new telescopes mean that before too long, scientists should be in a better position to find real moons if they're out there. Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF MECO SONG, "MOONDANCER")
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