Discovery of exoplanets with gravitational waves

In a recent article in Nature Astronomy, researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute / AEI) in Potsdam and the French Committee of Alternative Energies and Atomic Energy (CEA) in Saclay, Paris, suggest how the A planned space-based gravitational wave observatory that LISA can detect exoplanets orbiting binaries of white dwarves throughout the Milky Way and nearby magellanic clouds. This new method will overcome some of the limitations of current electromagnetic detection techniques and could allow LISA to detect planets up to 50 Earth masses.

Over the last two decades, the knowledge of exoplanets has grown considerably and more than 4000 planets have been discovered in orbit around a wide variety of stars. Until now, the techniques used to find and characterize these systems are based on electromagnetic radiation and are limited to the solar neighborhood and to certain parts of the galaxy.

In a recent article published in Nature AstronomyNicola Tamanini, researcher at the IEA in Potsdam and her colleague, Camilla Danielski, researcher at CEA / Saclay (Paris) show how these limitations can be overcome by gravitational wave astronomy. "We propose a method that uses gravitational waves to find exoplanets that revolve around white binary dwarf stars," says Nicola Tamanini. The white dwarfs are very old and small remains of stars that once resembled the sun. "LISA will measure gravitational waves from thousands of binaries of white dwarves." When a planet gravitates around such a pair of white dwarfs, the gravitational wave pattern observed will be different from that of the first one. 39, a binary without a planet This characteristic change of the gravitational waveforms will allow us to discover exoplanets. "

The new method exploits the Doppler shift modulation of the gravitational wave signal caused by the gravitational pull of the planet on the binary white dwarf. This technique is analogous to the gravitational wave of the radial velocity method, a well known technique used to find exoplanets with standard electromagnetic telescopes. The advantage of gravitational waves however lies in the fact that they are not affected by stellar activity, which can hinder electromagnetic discoveries.

In their article, Tamanini and Danielski show that the next mission of ESA, LISA (Laser Interferometer Spatial Antenna), whose launch is scheduled for 2034, can detect Jupiter's mass exoplanets around white dwarf binaries everywhere. in the galaxy, thus overcoming the distance limits of electromagnetic telescopes. . In addition, they emphasize that LISA will have the potential to detect these exoplanets also in neighboring galaxies, which could lead to the discovery of the first extragalactic-bound exoplanet.

"LISA will target a population of exoplanets still undefeated," says Tamanini. "From a theoretical point of view, nothing prevents the presence of exoplanets around compact white dwarf dwarfs." If these systems exist and are discovered by LISA, scientists will get new data to further develop the theory of planetary evolution. They will better understand the conditions in which a planet can survive the stellar phase of the red giant and also test the existence of a second generation of planets, that is to say, planets that are formed after the phase of the giant red. On the other hand, if LISA does not detect exoplanets orbiting binaries of white dwarves, scientists will be able to impose constraints at the final stage of the planetary evolution of the planet. Milky Way.