spaceSpace and Physics

Kepler Could Soon Spot Extrasolar Moons


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockFeb 15 2017, 17:36 UTC

This is what an exomoon might look like. NASA/JPL-Caltech

The planet-hunting telescope Kepler might soon spot something we’ve never seen before: A moon orbiting an extrasolar planet, otherwise known as an exomoon.

In a paper published in the Monthly Notices of the Royal Astronomical Society, Amy Barr and Megan Bruck Syal have estimated that planetary collisions could create massive moons around exoplanets, and that we already have the technology to detect them.


The researchers have highlighted how a powerful impact against a super earth, two to seven times the mass of our planet, could create a large stable moon the size of Mars. Such an object could be seen by Kepler.

“Our results are the first to demonstrate the masses of the moons that could form in the varied set of impact conditions possible within exoplanetary systems,” Barr, a senior scientist at Planetary Science Institute, said in a statement. “Most importantly, we have shown that it is possible to form exomoons with masses above the theoretical detection limits of the ongoing Hunt for Exomoons with Kepler survey, moons of more than a tenth of an Earth mass.”

The starting point for the research was the formation of our Moon, which is believed to have come into existence after an object the size of Mars slammed into the primordial Earth. The scientists used the same simulations used for the Earth-Moon system but on a larger scale.


“These outcomes are broadly similar to the Moon-forming impact, but when two super-earths collide, the disk is much hotter and more massive,” added Barr. And this leads to larger and heavier moons than what we see in the Solar System. The biggest natural satellite in our corner of the universe is Ganymede, a moon of Jupiter, which is 2.5 percent the mass our Earth.

This research has a companion paper, which will appear in the Astronomical Review, looking at all the possible ways to form natural satellites and investigating which are likely to be seen in extrasolar systems.

“Some of the old theories about the formation of Earth’s Moon, for example, fission, could operate in other solar systems,” said Barr. “With new observatories coming online soon, this is a good time to revisit some of the old ideas, and see if we might be able to predict how common exomoons might be, and what it would take to detect them.”

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