First exomoon possibly found: Neptune-Sized World Possibly Spotted Orbiting Alien Planet

First discovery of a moon outside of our solar system.

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Scientists may have bagged the first-ever exomoon.

NASA's Kepler and Hubble space telescopes have spotted evidence of a Neptune-size satellite orbiting the Jupiter-like planet Kepler-1625b, which lies about 8,000 light-years from Earth, a new study reports.

"We've tried our best to rule out other possibilities such as spacecraft anomalies, other planets in the system or stellar activity, but we're unable to find any other single hypothesis which can explain all of the data we have," co-author David Kipping, an astronomer at Columbia University in New York, told reporters earlier this week.

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The candidate exomoon orbits 1.9 million miles (3 million kilometers) from its host planet — about eight times farther away than Earth's moon circles. But because it's so big, the object would be about twice as big in Kepler-1625b's skies as Earth's moon is in ours, Teachey and Kipping said.

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Kepler-1625b appears to orbit in its star's habitable zone, the just-right range of distances where liquid water might be stable on a world's surface. But the moon is so big that it's almost certainly gaseous, with no discernible surface, Teachey said.



An artist’s illustration of the exoplanet Kepler-1625b with its large hypothesized moon. The pair have a similar mass and radius ratio to the Earth-moon system, but scaled up by a factor of 11.

Kepler-1625

Kepler-1625 is a 14th magnitude Sun-like star located in the constellation of Cygnus approximately 7000~8,000 light years away. It is just under 80% larger in radius than the Sun and has about 8% more mass. In 2016, it was discovered that the star is orbited by an exoplanet, Kepler-1625b, which is a gas giant orbiting within the system's habitable zone. In 2018, it was reported that this exoplanet might have an exomoon orbiting it.[6] This possibility will be verified on October 29, during the planet's next transit.