Dark matter with masses below 1 GeV can scatter, become captured, deposit annihilation energy, and increase the heat flow within extrasolar gas giants, rogue planets and brown dwarfs peppered throughout the Milky Way Galaxy, according to a paper published in the journal Physical Review Letters.
“We believe there should be about 300 billion exoplanets that are waiting to be discovered,” said Dr. Juri Smirnov, a researcher in the Department of Physics and the Center for Cosmology and Astroparticle Physics at the Ohio State University.
“Even finding and studying a small number of them could give us a great deal of information about dark matter that we don’t know now.”
“When the gravity of exoplanets captures dark matter, the dark matter travels to the planetary core where it annihilates and releases its energy as heat. The more dark matter that is captured, the more it should heat up the exoplanet.”
This heating could be measured by the future James Webb Space Telescope, an infrared telescope that will be able to measure the temperature of distant exoplanets.
“If exoplanets have this anomalous heating associated with dark matter, we should be able to pick it up,” Dr. Smirnov said.
“Exoplanets may be particularly useful in detecting light dark matter. Researchers have not yet probed light dark matter by direct detection or other experiments.”
Scientists believe that dark matter density increases toward the center of our Milky Way Galaxy.
If that is true, they should find that the closer planets are to the Galactic center, the more their temperatures should rise.
“If we would find something like that, it would be amazing. Clearly, we would have found dark matter,” Dr. Smirnov said.
Dr. Smirnov and his colleague, Dr. Rebecca Leane from the SLAC National Accelerator Laboratory at Stanford University, propose one type of search that would involve looking close to Earth at super- Jupiter exoplanets and brown dwarfs for evidence of heating caused by dark matter.
One advantage of using planets as dark matter detectors is that they don’t have nuclear fusion, like stars do, so there is less background heat that would make it hard to find a dark matter signal.
In addition to this local search, the team suggests a search for distant rogue exoplanets that are no longer orbiting a star.
The lack of radiation from a star would again cut down on interference that could obscure a signal from dark matter.
“One of the best parts of using exoplanets as dark matter detectors is that it doesn’t require any new types of instrumentation such as telescopes, or searches that aren’t already being done,” Dr. Smirnov said.
Rebecca K. Leane Juri Smirnov. 2021. Exoplanets as Sub-GeV Dark Matter Detectors. Phys. Rev. Lett 126 (16): 161101; doi: 10.1103/PhysRevLett.126.161101