133 light-years away, astronomers may have spotted a ‘monster’ exomoon for the first time

Scientists might have, for the first time, discovered an exomoon, a body similar to our Moon, but way beyond our solar system. NASA officially confirmed in September this year that it had, to date, found a whopping 6,000 exoplanets. But exomoons only existed in theory, and none had ever been found. However, some astronomers now claim that they might have stumbled across the first exomoon. The candidate in contention to be officially declared the first exomoon resides 133 light-years from Earth and orbits HD 206893 B, a Jupiter-like exoplanet. The researchers used a new approach to identify any exomoons near this planet. They repurposed high-precision astrometry, a mathematical approach to mapping out stellar distance, to check for moons. And they seem to have tasted success.

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While the planet is equal to the mass of 28 Jupiters, its exomoon is around 0.4 Jupiter masses. This is around the size of seven Neptunes put together, the scientists said. This makes it an exomoon of monstrous proportions. The paper submitted by a group of astronomers led by Quentin Kral of the Paris Observatory in France is currently available as a preprint. It still needs to be checked and verified by other astronomers. Even though their finding still needs to be confirmed by the wider community, they believe that astrometry will emerge as a promising method to detect exomoons.

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Why are exomoons hard to find?

Scientists have often come across bodies that they thought were exomoons, only to be disappointed. Exomoons are much smaller than their planets, based on how things work in our solar system. Discovering verified exoplanets itself is a task, since confirmation is based on rigorous and multiple checks. According to NASA, there are nearly 8,000 exoplanets waiting for official status. On the cosmological scale, exoplanets are already considered extremely small. Since exomoons are even smaller, detecting them has been nearly impossible. The study adds that "there is no definition of what an exomoon is, and some ambiguity remains as to whether it may include, for instance, binary planets."

The researchers added that this exomoon candidate has "a tentative nature" and needs further confirmation using GRAVITY data. If all goes well and the measurements stick, we might soon have out very first exomoon.