Discovery of a super moon outside our solar system

Astronomers have reported a large second moon orbiting a planet the size of Jupiter beyond our solar system. If confirmed, the sighting could mean that exolunas are as common in the universe as exoplanets, and that large or small, such moons are a feature of planetary systems. But it could be a long wait. The first ever sighting of an exoluna four years ago is still awaiting confirmation, and the verification of this new candidate could be just as long and controversial.

“Astronomers have found more than 10,000 exoplanet candidates so far , but exolunas are much more challenging, ”said David Kipping, of Columbia University's Cool Worlds Lab, who has spent the past decade chasing exolunas. “I am terra incognita.”

The team has identified the gigantic exoluna orbiting the planet Kepler 1708b, a world 5,500 light-years from Earth in the direction of the constellations of Cygnus and Lyra. This new candidate is about a third smaller than the Neptune-sized moon that Kipping and his colleagues previously found orbiting a similar Jupiter-sized planet Kepler 1625b.

Both. Candidate supermoons are likely made of gas that has accumulated under the gravitational pull caused by their enormous size, Kipping said. If the hypothesis is correct, the moons may also have started their life as planets, only to be dragged into the orbit of an even larger planet such as Kepler 1625b or 1708b.

Europa, the icy moon of Jupiter. Credits: NASA / ESA / W. Sparks (STScI) / USGS Astrogeology Science Center



Both moons are located far from their host star, where there is less gravity to attract the planets and strip them of their moons. Indeed, the researchers searched for cold, giant gas planets on wide orbits in their search for exolunes precisely because the analogues in our solar system, Jupiter and Saturn, have more than a hundred moons in total.

If there are any. other moons out there are likely to be smaller, but also harder to spot, Kipping said. Exolunas fascinate astronomers for the same reasons as exoplanets. They have the potential to reveal how and where life may have emerged in the universe. Astronomers want to know how these exolunas form, whether they can support life, and what role, if any, they play in making their host planets habitable.

In the present study, researchers looked at giant planets cold gases identified by the NASA spacecraft, Kepler. After scanning 70 planets deep, they found only one candidate, Kepler 1708b, which emits a Moon-like signal. Observations from other space telescopes, such as Hubble, will be needed to verify the discovery, a process that could take years. Four years after the first discovery, exolons continue to be hotly debated.

Eric Agol, a professor of astronomy at the University of Washington, said he doubts that the latter signal will prove to be real. “It could just be a fluctuation in the data, due to the star or the instrument noise,” he said.