How NASA Plans to Hunt Hidden Exoplanets Using Gravitational Waves

Invisible planets may soon reveal themselves through ripples in the fabric of space itself. Scheduled for launch in the mid-2030s, the European Space Agency's LISA observatory will detect gravitational waves, the tiny fluctuations produced by massive orbiting objects. Two new studies led by NASA astrophysicists show how these ripples can expose exoplanets hidden in tightly orbiting double white dwarf systems.

This method could uncover a totally new population of distant worlds that traditional light-based telescopes miss. Double white dwarf systems emit continuous gravitational waves as they orbit one another. If a sufficiently massive planet circles that pair, its gravity pulls on the stars and creates a reflex motion.

Scott Noble, a theoretical astrophysicist at NASA Goddard, explains that this movement adds a Doppler modulation to the gravitational signal, much like a radio carrier frequency forming sidebands. For LISA, this appears as secondary signals at higher and lower frequencies that carry the signature of a planet. Our read: this turns space-time itself into a cosmic antenna, picking up planetary whispers that light alone cannot catch.

While LISA can spot a Jupiter-mass planet thousands of light-years away, confirming those discoveries requires a different tool.

Mary Anne Limbach and her co-authors outline a method using the infrared-sensitive James Webb Space Telescope to validate the findings.

A planet orbiting white dwarfs creates an infrared excess that Webb can detect up to 500 light-years away.

For a test system at that distance, researchers calculate that Webb can spot an exoplanet about five times the mass of Jupiter.

Yet, the source notes that no planets have actually been found around a binary white dwarf yet, meaning these predictions rely entirely on models until LISA reaches orbit.