The first known moon might have been detected by astronomers outside our solar system, New Scientist reported.
Exomoons have long been predicted to exist, offering the tantalizing possibility that some of them may be habitable worlds. Though there have been no confirmed reports of an exomoon yet, the new moon, which is 1,800 light years from Earth, and its exoplanet have been discovered by astronomers adrift in the cosmos, far from any star.
Most of the 1,000 exoplanets that have been discovered to date have been found through analyzing changes in the light of the star. A few others have been seen by using a technique called gravitational microlensing, according to New Scientist.
When an object passes in front of a distant star as seen from Earth, the object's gravity bends the light from the background star, focusing it like a lens - and making the star temporarily appear brighter if observed from a particular angle, New Scientist reported.
David Bennett of the University of Notre Dame, Indiana, and colleagues said they spotted a microlensing event in 2011, using a number of telescopes around the world. First they saw the distant star's light amplified to 70 times its normal brightness. An hour later came a second, smaller increase in brightness, New Scientist reported. This indicates that a large object passed in front of the star, followed by a smaller one.
Whether the two objects were a moon and its planet is uncertain. However, the team came up with two possible scenarios that fit the microlensing data.
In the first case, the pair of objects is relatively near to our solar system, at a distance of about 1,800 light years, and consists of a planet around four times the mass of Jupiter and a moon about half the mass of Earth - and thus many times more massive than our Moon, according to New Scientist.
If this is true, then the team has discovered the first exomoon.
However, in the other scenario, the pair of objects is much further away and consists of a very small star or a failed star known as a brown dwarf, orbited by a Neptune-mass planet, New Scientist reported.
