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More than 4,000 exoplanets are now known to orbit other stars. Indeed, astronomers suspect that such worlds are ubiquitous, estimating that, on average, every star in the Milky Way must have at least one planetary companion. But therein lies the rub: Although exoplanets seem to pop up everywhere, “everywhere” is far from the truth in describing where astronomers have actually looked. The vast majority of exoplanet surveys have stuck to either stars closely neighboring the sun or those farther off, in the direction of the Milky Way’s central galactic bulge. Truth be told, no one yet knows the true abundance of planets throughout the Milky Way or, for that matter, the prevalence of planets in galaxies other than our own.

According to a study published on July 8 in Nature Astronomy, a major step toward completing this exoplanet census could begin in 2034, with the launch of the European Space Agency’s LISA mission. LISA stands for Laser Interferometer Space Antenna, a name that hints at the mission’s primary purpose: to detect ripples in spacetime—gravitational waves—by looking for minuscule changes in the distances between three satellites arranged in a triangular constellation with sides 2.5 million kilometers long. LISA will be custom-built to tune in to gravitational waves from merging supermassive black holes, but it could apparently listen to gravitational waves from some exoplanet systems, too.

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