A new European Space Agency instrument called LISA (Laser Interferometer Space Antenna) that’s set to launch in 2034 will use gravity waves to find exoplanets, pushing the distance available for exoplanet detection beyond our home galaxy. NASA has over 4,000 confirmed exoplanets in its catalog so far, but all of them are within the boundaries of the Milky Way due to constraints on current observational tools. A paper recently published in Nature Astronomy detailed the proposed technique as described by researchers from the Max Planck Institute for Gravitational Physics in Potsdam, Germany and the French Alternative Energies and Atomic Energy Commission in Paris, France.
“This [instrument-limited] selection problem prevents us from unveiling the true galactic planetary population,” the abstract of the paper states. “Here, we present a detection method…that will allow us to detect massive exoplanets using gravitational-wave astronomy.” LISA will target binary white dwarf systems specifically and will be sensitive enough to detect exoplanets down to 50 Earths size.
White dwarf stars are the core remains of stars like our Sun after they’ve consumed all of their fuel. After all the hydrogen in a low-mass star is used, it cools and expands into a red giant, burning off the remaining helium. Once the helium is gone, the star unsuccessfully tries to combine the remaining carbon and releases the gases into a planetary nebula with a carbon-dense white dwarf in the center. Since any planets orbiting within the star’s red giant range will be incinerated, any exoplanets detected in orbit around the white dwarf are considered to be part of a second generation.
Any new method of discovering and/or learning about exoplanets is always exciting. I personally think it’s so cool that, in addition to contributing general relativity, Einstein also predicted the existence of this tool. In other words, we are using Einstein’s gravity waves to find exoplanets!
Since white dwarf stars still emit tons of heat and can last longer than our universe has been around, it’s feasible that any surviving planets in orbit around one dwarf (or two, in this study’s case) could host an advanced civilization.
Actually, that’s something the ancient alien community has proposed (among others). The Dogon tribe of Africa claims their ancestral gods came from the Sirius system, specifically a planet orbiting an undiscovered Sirius C star. Their lore supposedly references Sirius B, a white dwarf, as an invisible companion star to Sirius, even mentioning that it’s very heavy (one teaspoon of a white dwarf weighs as much as an elephant). A quick search on Google or Amazon will list the extensive research, study, and speculation that has gone into this legend. A recent Ancient Aliens episode was focused on it as well.
Alien legends aside, though, how amazing would it be to detect planets that exist outside our own galaxy? Honestly, I’m usually so focused on the closest stars to us (see again: aliens or a second human home) that I didn’t really stop to think about where all of the detected exoplanets were located. Of course, detecting extragalactic planets would probably also come as a big tease as our instruments need to be developed even more before we could learn things about their compositions and (potential) residents.