Astronomers will have their best shot yet at finding exomoons – alien moons that orbit planets beyond the solar system – after efforts to look for them were picked for the next phase of observations with the James Webb Space Telescope (JWST).
Exomoons may be interesting locations to look for life, but no definitive detection of one has ever been made. JWST, which launched in 2021, is the first telescope in history capable of truly confirming their existence.
Every year, astronomers make proposals to the Space Telescope Science Institute (STScI) in the US, which runs JWST, for what the telescope should look at. This year’s selections were the most competitive ever, with a record 1931 programmes submitted. Only 253 proposals – roughly one in eight – were selected to make up part of JWST’s overall programme, called Cycle 3.
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Exomoon projects had never before been picked for JWST, but in the Cycle 3 selections announced on 29 February, they finally made the cut. The STScI chose five programmes related to exomoons, including two that would perform direct hunts for them. “It’s still kind of a shock,” says at Columbia University in New York, who leads one of the programmes. “I’m very excited.”
Cassese’s programme will study orbiting a star called Kepler-167, which is about 1110 light-years from the solar system. The planet crosses the face of its star from our point of view once every 1000 days, causing a dip in light known as a transit.
The next crossing is in October, and Cassese’s team will watch it with JWST to look for evidence of one or more exomoons causing additional transits. , also at Columbia University and part of the team, says the planet is “our best target” to look for an exomoon given its size and distance from its star.
Another programme, led by at Harvard University, will look for exomoons orbiting two planets around the red dwarf star TOI-700, about 100 light years from Earth. The two planets are Earth-sized and in the habitable zone, says Pass, which makes them “prime targets to search for moon-sized moons”.
The selection of these two programmes is “a significant milestone in the exomoon field”, says at the University of Michigan. “This marks the first cycle in which JWST has selected not just one, but two exciting proposals focused on the search for exomoons.”
Three other programmes will perform more indirect studies of exomoons. One will look at , which could include exomoons. Another will study the same planet as Cassese’s team to about it. And a third will observe a ring of hot material caused by two planets colliding, which could be a way moons form.
But it is Cassese and Pass’s programs that will be of most interest to exomoon hunters, possibly giving us our first true detection of moons orbiting exoplanets. “Regardless of whether there are moons found, we’ll learn something interesting about those systems,” says at the Massachusetts Institute of Technology. “I’m crossing my fingers for seeing something totally revolutionary.”
