&Bullet; physics 14, p46
Measuring the temperatures of massive exoplanets could reveal the effects of dark matter and potentially allow researchers to confirm the galactic distribution of this mysterious substance.
For dark matter detectors, larger is usually better because it means the detector can potentially interact with more dark matter particles. But even the largest ones are tiny compared to a newly proposed detector  . Rebecca Leane from Stanford University’s SLAC National Accelerator Laboratory and Juri Smirnov from Ohio State University, Columbus, suggest looking for dark matter by measuring its influence on the temperatures of exoplanets and brown dwarfs up to 55 times the mass of Jupiter . With tens of thousands of suitable exoplanets expected to be found in the next five years, these measurements could detect or rule out dark matter particles with masses greater than that of an electron.
The prevailing model of the distribution of dark matter in the universe provides that our galaxy sits in a spherical “halo” of dark matter, the density of which increases towards the galactic center. Occasionally, a particle of dark matter in this halo may be scattered by an electron or nucleon in an astronomical body before it is caught by the body’s gravity. Some hypothetical forms of dark matter annihilate to create photons and other particles, meaning that if a significant amount of dark matter particles accumulate, they could heat a body.
Leane and Smirnov show that for gas giants orbiting stars on Earth, this warming could be measurable with NASA’s James Webb Space Telescope, which will be launched shortly. The telescope could also detect the signal in more distant brown dwarfs and “rogue” exoplanets (planets with no parent stars), with those closest to the Galactic Center likely to have the highest dark matter capture rates and the highest temperatures. These measurements not only provide information about the nature of dark matter, but can also reveal parameters of the dark matter halo such as the density profile.
Marric Stephens is Corresponding Editor for physics based in Bristol, UK.
- RK Leane and J. Smirnov, “Exoplanets as Sub-GeV Detectors for Dark Matter”, Phys. Rev. Lett.126161101 (2021).