Astronomers identify the second exomoon candidate in the universe

The discovery of a second exomoon candidate outside our solar system raises the possibility of more discoveries and that these moons are as common as exoplanets .


In 2017 a group of astronomers claimed to have “convincing evidence” of the first moon  orbiting a planet outside our solar system and now the same team reports the discovery of a second; If confirmed, it is a first step to think that exomoons would be as common as exoplanets .

The description of this supermoon is published in the scientific journal Nature Astronomy and if its status as an exomoon is confirmed , ” Kepler-1708 bi ” -which is 2.6 times larger than Earth- could represent one of the missing pieces in the puzzle of the formation and evolution of extrasolar planetary systems.

A long wait

According to the researchers, led by David Kipping of Columbia University (United States), “it could also mean that exomoons are as common in the universe as exoplanets , and that, large or small, they are a feature of planetary systems.

But the wait, they warn, could be long. The first finding of an exomoon , four years ago, is still pending confirmation and verification of this new candidate could be just as long and controversial.

“Astronomers have found more than 10,000 exoplanet candidates so far, but exomoons are much more challenging,” Kipping summarizes in a note from Columbia University.

Specifically, the team discovered a giant exomoon candidate orbiting the planet Kepler 1708b , a world located 5,500 light-years from Earth. This is about a third smaller than the moon previously found orbiting the planet Kepler 1625b.

Both are probably made up of gas that has accumulated under the gravitational pull caused by their enormous size, Kipping details.

For the study now being published, the researchers examined the coldest gas giant planets captured by NASA’s Kepler space observatory; After thoroughly analyzing 70 planets, they only found one candidate – Kepler 1708b – with a signal similar to that of a moon.

Observations from other space telescopes, such as Hubble, will be needed to verify the discovery, a process that could take years. In fact, four years later, Kipping’s first discovery of an exomoon is still hotly debated.

As reported by Columbia University, in a recent paper, he and his colleagues showed how a group of skeptics may have missed Kepler’s moon 1625b in their calculations.

Eric Agol, professor of astronomy at the University of Washington, points out – in the same statement – that he has doubts that the latter is real: “It could simply be a fluctuation in the data, either due to the star or to instrumental noise. “.

Others are more optimistic. “This is science at its finest,” says Michael Hippke, an independent astronomer in Germany: “We find an intriguing object, make a prediction and confirm the exomoon candidate, or rule it out with future observations.”

“I’m very excited” about the possibility of seeing a second exomoon candidate, although “it’s a shame that only two transits have been observed,” says Hippke, who adds: “It would be very interesting to have more data.”

Discovering a moon or even a planet hundreds or thousands of light years from Earth is anything but easy, the university recalls.

The moons and planets can be observed only indirectly, because they spend in front of their host stars, making the light from the star dims intermittently; Picking up one of these fleeting traffic signals with a telescope is tricky, as is interpreting the light curve data.

The moons are even harder to detect because they are smaller and block less light, but the search is worth it, emphasizes Kipping.

The researcher recalls how the existence of exoplanets was received with the same skepticism at first: “These planets are strange compared to our system, but they have revolutionized our understanding of how planetary systems form.” (EFE)