Astronomers have announced the possible discovery of the first known moon outside our Solar System, also known as exomoon.
This “exomoon” is not like any in our cosmic neighborhood: it’s the size of Neptune and orbits a planet the size of Jupiter – but with 10 times the mass.
The object was spotted in data from Nasa’s Kepler spacecraft, and later observed using the Hubble telescope.
The astronomical “discovery” were presented by astronomers David Kipping and Alex Teachey and published their results in Science Advances journal.
Both experts said that further observations are needed to understand the distant planetary system.
“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,” said Dr Kipping, from Columbia University in New York.
To date, astronomers have discovered more than 3,500 exoplanets – worlds orbiting stars other than the Sun.
A hunt for exomoons – bodies that orbit these distant planets – has proceeded in parallel. But so far, these natural satellites have lingered at the limits of detection with current techniques.
The researchers monitored a planet known as Kepler 1625b as it passed in front of its parent star.
This 19-hour event, known as a transit, blocked out some of the light coming from the star, which lies at a distance of 8,000 light-years from Earth.
This is exactly what the researchers saw: “The location, shape and depth of this event appear consistent with a Neptune-sized moon transiting in front of the star,” said Dr Kipping.
Furthermore, both objects are gas giants and the apparent moon, known as Kepler 1625b-i, orbits some three million kilometers from the planet.
About 3.5 hours after the planet’s transit ended, the Hubble telescope recorded a second smaller dimming of the star’s brightness, which indicated a moon “trailing the planet like a dog following its owner on a leash,” according to Dr Kipping.