LISA Mission Will Detect Exoplanets in Double White Dwarf Systems
An upcoming space-based observatory designed to detect gravitational waves will also find an entirely new population of exoplanets across the Milky Way, Media Indonesia reported.
Two recent studies led by NASA astrophysicists and published in The Astrophysical Journal outline how the Laser Interferometer Space Antenna (LISA) can uncover planets in binary white dwarf systems. The presence of a planet inside these systems leaves a distinct imprint on gravitational wave signals.
The most common source for LISA is expected to be double white dwarf systems, which are binaries composed of white dwarfs in very tight orbits,
Casey McGrath, a postdoctoral researcher at the University of Maryland, Baltimore County and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, told Media Indonesia.
If an exoplanet also orbits within one of these systems, its presence becomes imprinted on the gravitational wave signal in a way that we will be able to reveal,
McGrath added.
The LISA detection method shares principles with the radial velocity technique, which uses light to find exoplanet candidates near nearby stars. As a planet orbits, its gravity pulls on the host star to produce a small wobble through the Doppler effect.
Something similar happens with gravitational waves,
Scott Noble, a theoretical astrophysicist at NASA Goddard and co-author of the confirmation paper, told Media Indonesia. By themselves, double white dwarfs emit gravitational waves at a nearly continuous frequency.
Noble explained that adding a massive planet causes the binary system to experience a reflex motion, which adds Doppler modulation to the gravitational signal. For LISA, this modulation appears as sidebands, or secondary signals at frequencies higher and lower than the primary frequency.
White dwarfs are Earth-sized remnants of stars like the Sun. While exoplanets are known around a few isolated white dwarfs, none have been found around binary white dwarfs yet.
Astronomers estimate the Milky Way contains millions of double white dwarf systems with orbital periods under one hour. LISA is expected to detect roughly 10,000 individual systems.
To confirm these discoveries, scientists plan to rely on the infrared sensitivity of NASA’s James Webb Space Telescope (JWST). Once LISA catches its first exoplanet detection, it will be crucial for us to validate some of them,
Mary Anne Limbach, a research scientist at the University of Michigan, told Media Indonesia.
These combined detections will allow us to establish that the gravitational signal corresponds to a true planet rather than a false positive,
Limbach said.
The LISA mission is scheduled to launch in the mid-2030s. It will use three spacecraft flying in a triangular formation separated by millions of miles, utilizing high-precision infrared laser beams to measure microscopic distance changes.