In our solar system there are hundreds of moons of various sizes and characteristics. We’ve seen them, and we’ve even sent ships to some of them. But outside of it we do not know a single one . Or we did not know, because a team of researchers from the Astronomy department of Columbia University (United States) has announced the detection of a possible star that would orbit the exoplanet Kepler-1625b (located 4,000 light years from Earth). It could be the first exomoon seen by human eyes. His name, Kepler-1625b I.
The finding has aroused great interest among scientists, since moons represent a great source of information about the universe. They give clues about the mechanisms that make up planets and planetary systems like ours, and the characteristics of some of them – atmospheres, internal sources of heat, presence of water … – have made them candidates to be the first places in the universe in those of us who find ways of life.
¿ Exoluna o no?
The observation was carried out by a team led by British astronomer David Kipping, principal investigator of the HEK (Hunt for Exomoons with Kepler) initiative, a project that tracks the presence of exomoons with the help of NASA’s Kepler space telescope. HEK started in 2011, but had so far found no sign of astronomical dams.
In recent times, Kipping and his collaborators have focused on 284 exoplanets that they suspected might have exomoons orbiting them. To further refine the shot (it must be taken into account that more than 2,500 planets have already been discovered outside the solar system), they chose candidates with sizes between that of Earth and that of Jupiter, and located at a distance from their star of between 15 and 150 million kilometers.
But how did they come to the conclusion that the body they called Kepler-1625b I is a Neptune-sized moon circling a planet as large as Jupiter? To find exoplanets, astronomers look for small temporary dips in a star’s apparent brightness that indicate a planet is in transit around it.
The same is done to detect exomoons, although the difficulty is much greater, for several reasons. To begin with, the planets, in addition to being smaller than their stars, do not emit light, they reflect it, so their brightness is much lower. And on the other hand, the smallness of the moons complicates the task even more. It is very difficult for observers to distinguish the signal emitted by a moon from that coming from its planet, especially if we are talking about systems located 4,000 light years away, as in the case at hand.
Hubble has the last word
Kipping and his colleagues have confirmed that they detected three of these alterations in the brightness of the exoplanet Kepler-1625b. They have been attributed to the presence of an exomoon, which in addition to being the first found, would be the largest known.
However, they remain cautious, like good scientists. They are scheduled to use the Hubble space telescope (much more accurate than Kepler) in October to confirm whether we are in front of our first exomoon.
Photo (NASA / JPL-Caltech): Illustration of an exomoon orbiting a gas giant planet in the habitable zone of a star. The artist has imagined a moon similar to Earth and with conditions to host life.
