Astronomers may have found the first moon outside our solar system
Astronomers may have found the first moon outside our solar system.
The so-called "exomoon", which is estimated to be the size of Neptune, was found in orbit around a gigantic gas planet 8,000 light-years from Earth.
It was spotted in data from Nasa's Kepler spacecraft, and later observed using the Hubble telescope.
Astronomers David Kipping and Alex Teachey published their results in Science Advances journal.
However, the pair are cautious about confirming the find as an exomoon and say more observation is needed.
"The first exomoon is obviously an extraordinary claim and it requires extraordinary evidence," Teachey said.
"Furthermore, the size we’ve calculated for this moon, about the size of Neptune, has hardly been anticipated and so that, too, is reason to be careful here."
He added: "We’re not cracking open Champagne bottles just yet on this one."
If indeed a moon, it would be about two million miles (three million kilometers) from its planet and appear twice as big in its sky, as the moon does in ours.
The astronomers are uncertain how this potential moon might have formed, given its size.
"If confirmed, this finding could completely shake up our understanding of how moons are formed and what they can be made of," NASA’s science mission chief Thomas Zurbuchen said in a statement.
However, given that both the planet and its potential moon are gas giants, no one is suggesting conditions that might support life.
"But going forward, I think we’re opening the doors to finding worlds like that," Teachey said.