Gravitational Waves Could Reveal Planets Around Dead Stars

Most planets announce themselves in light, as a dip when they cross their star or a wobble in the star's spectrum. Two papers published on November 10, 2026, in The Astrophysical Journal describe a quieter route. They show how the Laser Interferometer Space Antenna, LISA, could reveal planets orbiting pairs of white dwarf stars by detecting the planets' gravitational tug inside a gravitational-wave signal.

The lead author of both studies is Casey McGrath, a postdoctoral researcher at the University of Maryland, Baltimore County and NASA's Goddard Space Flight Center in Greenbelt, Maryland. The first paper, McGrath's alone, works out the detection method and maps the planet masses and orbital periods where it performs best. The second, written with coauthors, asks how such a planet could be confirmed once LISA flags it.

The targets are double white dwarf systems, two stellar remnants in tight orbits. They're expected to be LISA's most common source, and their steady gravitational-wave hum is precisely what makes a planet detectable. A planet orbiting the pair tugs the whole system, and that tug shifts the hum in a way the observatory can, in principle, read. Japanese astronomer Naoki Seto first proposed the idea in 2008.

The reach is the striking part. NASA's summary of the work says LISA could detect a Jupiter-mass planet thousands of light-years away, and under ideal circumstances a world smaller than Jupiter. That's a population no light-based survey can touch, because white dwarfs are faint and their planets fainter. Gravitational waves don't care how dim the system is, only how its mass moves.

Confirmation is where the James Webb Space Telescope enters. A gravitational-wave detection gives a position and an orbit but no picture. McGrath's second paper shows Webb could confirm a nearby candidate by its extra infrared glow, out to at least 500 light-years. In the test case at that distance, Webb could pick out a planet about five times Jupiter's mass. Two instruments, two kinds of evidence, one planet.

None of this happens soon, and the papers don't pretend otherwise. LISA is led by the European Space Agency with NASA as a partner, and it's slated for launch in the mid-2030s. Its three spacecraft will trail Earth around the Sun in a triangle with sides of 2.5 million kilometers, listening for ripples from across the galaxy. The method published this week is a plan for an observatory that doesn't exist yet.

The scientific payoff, if the plan holds, is a census of a hidden population. Planets around double white dwarfs are survivors, worlds that endured the deaths of two stars, and nobody knows how many of them there are. A detection method that works through gravity rather than light could count them for the first time, and every confirmed case would test what planetary systems become after their suns are gone.