Researchers in the U.S. have carried out the most stringent tests to date of the idea that an ultraviolet glow in the atmospheres of giant planets could partly arise through the indirect interaction between dark matter and ordinary matter. Led by Carlos Blanco at Princeton University, the team's results place some of the tightest constraints yet on the strength of this interaction.
Published in Physical Review Letters, the study also strengthens the possibility that the giant planets in our solar system could be used as natural dark matter detectors.
Ultraviolet airglow
When viewed through Earth's atmosphere, the night sky is never truly dark. After molecules in the atmosphere are ionized by the sun's radiation during the day, they can recombine and emit photons in a process that continues throughout the night.
Named "airglow," this phenomenon was first described more than 2,000 years ago. In 2024, however, Blanco and his colleague Rebecca Leane at the SLAC National Accelerator Laboratory proposed that a different atmospheric glow could emerge when hypothetical dark matter particles annihilate within giant planets.
As the solar system orbits the galaxy, the duo suggested that giant planets such as Jupiter could capture significant numbers of dark matter particles. As these particles annihilate, the energy released could ionize nearby molecules of hydrogen. The resulting ions quickly react to form triatomic hydrogen (H₃⁺), which emits infrared radiation as it relaxes into lower-energy states.
By comparing predictions of this infrared emission with observations of Jupiter's upper atmosphere, Blanco and Leane placed some of the first reliable constraints on whether dark matter interactions could produce a detectable atmospheric signature. However, that infrared signal relies on H₃⁺, making it far more specific to individual planetary atmospheres.
"The natural next question was whether there's a signature that works on every giant planet at once," Blanco says. "Ultraviolet airglow, a phenomenon that humans have wondered about since Aristotle, turned out to be the answer."
Revisiting planetary flybys
In their latest study, Blanco, Leane and their colleagues investigated another possible consequence of dark matter annihilations. Instead of looking for infrared emission from H₃⁺, they examined whether energetic electrons produced during the ionization process could excite molecular hydrogen directly, causing it to emit ultraviolet light.
"Alongside ionizing photons, ionizing electrons can also cause molecular hydrogen to glow in the ultraviolet, a signature we can search for in every giant planet at once," Blanco explains.
Since any dark matter-induced glow would likely be overwhelmed by sunlight, the team focused on observations of the planets' nightsides. At the faint light levels predicted by the theory, suitable measurements are available only from spacecraft flybys. To date, these have been provided by Voyager 1, Voyager 2 and New Horizons during encounters with Jupiter, Saturn, Uranus and Neptune.
Because giant-planet atmospheres already produce faint ultraviolet nightglow through natural processes, the researchers searched for any additional emission that could be attributed to dark matter. By requiring that the predicted dark matter signal remain no brighter than the ultraviolet glow actually observed by the spacecraft, they placed new constraints on the theory—yielding some of the tightest limits to date on interactions between dark matter and ordinary matter.
Planets as dark matter detectors
The team's findings strengthen the case for using the solar system's four giant planets as natural dark matter detectors. In particular, they could probe regions of dark matter parameter space that are inaccessible to underground experiments on Earth, including very light particles and strongly interacting dark matter that would be stopped before reaching terrestrial detectors.
"The sensitivity peaks for dark matter near the mass of the proton, which transfers energy most efficiently to the hydrogen these planets are made of," Blanco explains. "Because the four giant planets differ in size, temperature and composition, each one probes different dark matter masses and models."
At the same time, the predicted sensitivity raises new questions about the behavior of dark matter after it is captured by a planet. In particular, planetary heat could allow the lightest dark matter particles to escape before they produce an observable atmospheric signature, reducing the sensitivity of the technique.
The researchers hope many of these questions can be addressed by future missions, including ESA's JUICE spacecraft, which is due to enter Jupiter's orbit in 2031. "JUICE carries an ultraviolet spectrometer, and a proposed Uranus mission could revisit the ice giants for the first time since Voyager 2," Blanco predicts.
"Future ultraviolet telescopes could search for this glow in massive exoplanets, where a nearby Super-Jupiter would be an exceptionally sensitive dark matter detector."
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Publication details
Carlos Blanco et al, Search for Dark Matter Induced Airglow in Planetary Atmospheres, Physical Review Letters (2026). DOI: 10.1103/g53c-cvnh
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Citation: Giant planets could act as dark matter detectors (2026, July 17) retrieved 17 July 2026 from https://phys.org/news/2026-07-giant-planets-dark-detectors.html
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