Jupiter’s equatorial zone and its Great Red Spot stand out in this infrared image from the James Webb Space Telescope because their high-altitude haze layers reflect sunlight well. Also note the bright auroral emissions near the giant planet’s north and south poles. Image credit: NASA/ESA/Jupiter ERS Team; image processing by Judy Schmidt
Dark matter is a mysterious substance that makes up about 85 percent of all the matter in our universe. Although we cannot see it, may You can see their gravitational fingerprints in the motion of galaxies and the way massive objects refract the light around them. And now researchers may have found a way to turn giant exoplanets into sensitive detectors for dark matter particles, researchers say — and a new study of our own planet Jupiter shows how the method would work.
The article appeared on June 27 in Physical examination letters.
Because dark matter permeates space, the researchers say the enormous gravity of gas giants should pull the dark matter particles into an invisible cloud that surrounds and penetrates them. There, collisions between dark matter particles in their upper atmospheres could produce light, as well as an increase in the amount of trihydrogen (H3+) There.
H3+ can form in a planet’s atmosphere in many ways, including interactions with cosmic rays, solar wind, and lightning. In this case, however, the researchers examined observations of Jupiter’s night side by the Cassini spacecraft, made when the spacecraft came within 10 million kilometers of the planet on its way to the Saturn system in 2000 and 2001. They concluded that looking at the night side, particularly at latitudes and times when Jupiter’s aurora is unlikely to be active, could reveal signs of dark matter annihilation around the giant planet.
They were unable to detect any such glow in Jupiter’s upper atmosphere. However, as with many “null results” in science, this is not bad news. Rather, the researchers used the lack of detection to calculate a maximum size for dark matter particles.
Setting a size limit for dark matter
A leading theory of dark matter is that it consists of so-called weakly interacting massive particles, or WIMPS. What exactly these particles might be is highly controversial. The WIMP model states that dark matter particles some Mass – in contrast to particles with zero mass, such as photons – and must be approximately the size of a proton.
These dark matter particles must constantly flow through all the planets in the solar system, but usually without interacting.
According to Dan Hooper, a particle astrophysicist at the University of Chicago who was not involved in the study, a rough calculation suggests that up to 1 kilogram of dark matter flies through Jupiter every second.
Because of the planet’s strong gravity, some of these particles must have formed an invisible cloud inside and around Jupiter that has been building up over billions of years. Collisions between these invisible particles could generate radiation. In theory, this radiation would create an excess of H.3+ This can be detected as infrared glow in Jupiter’s upper atmosphere, says Hooper.
The authors of the latest study had hoped to discover this glow.
But “when Cassini pointed its instruments at the night side of Jupiter, it saw absolutely nothing,” says dark matter physicist Carlos Blanco of Princeton University, the lead author of the study.
Such a lack of detection – known in science as a “null result” – is like Sherlock Holmes solving a puzzle because a dog doesn’t bark.
Blanco and his co-author, astroparticle physicist Rebecca Leane of Stanford University, have calculated that dark matter particles must have a cross section of less than 10.-38 cm2. In physics, the cross section of a particle depends on how likely it is that the particle will interact with other particles. And if dark matter particles were larger, they would interact more often and produce a detectable signal.
This cross section is smaller than what dark matter detection experiments can detect here on Earth, and the researchers say this shows the value of their approach.
“The kind of detectors you can set up in a laboratory on Earth are really only sensitive to dark matter particles that are heavier than hydrogen, and they lose sensitivity very quickly when the dark matter is lighter,” says Blanco. “We found that looking at signatures that dark matter might leave on molecules like H is generally3+ is a good way to break through this barrier and arrive at ever lighter particles.”
One step closer
The zero result on Jupiter is just the beginning.
The authors suggest that the infrared glow created by collisions between dark matter particles may be easier to detect in the atmospheres of exoplanets more massive than Jupiter, especially in regions with more dark matter – for example, near the center of our galaxy.
“What you really want is something big, like a ‘super Jupiter’ (a planet with more mass than Jupiter) that is closer to the galactic center, where there is a higher concentration of dark matter,” he says. “Then you would expect a stronger signal.”
It is currently not possible to detect such glow from exoplanets, but Blanco hopes that such technology will soon be developed. However, he points out that astronomers would need to improve the sensitivity of the relevant instruments by two to three times to be effective.
“That’s still a long way off,” says cosmologist Joseph Silk of Johns Hopkins University, who was not involved in the study.
Still, it’s another opportunity for astronomers to one day see the invisible and uncover the true nature of the mysterious dark matter that permeates our universe.
