Scientists use Jupiter to search for dark matter

Darkish matter is a mysterious substance that makes up some 85 p.c of the total matter in our universe. Though we can not see it, we can see its gravitational fingerprints on the best way galaxies transfer and the best way huge objects bend gentle round themselves. And now, researchers could have discovered a strategy to flip large exoplanets into delicate detectors for dark matter particles, say researchers — and a brand new examine of our personal planet Jupiter reveals how the strategy would work.

The paper was revealed June 27 in Physical Review Letters.

As a result of dark matter permeates space, the researchers say that the large gravity of gas giant planets ought to draw dark matter particles into an invisible cloud surrounding and permeating them. There, collisions between dark matter particles of their higher atmospheres may produce gentle, in addition to a rise within the quantity of trihydrogen (H₃⁺) there.

H₃⁺ will be created in a planet’s environment some ways, together with by way of interactions with cosmic rays, solar wind, and lightning. On this case, although, the researchers examined observations from the Cassini spacecraft of Jupiter’s nightside, made because the spacecraft got here inside 6.2 million miles (10 million kilometers) of the planet in 2000 and 2001, whereas on its strategy to the Saturn system. They reasoned that trying on the nightside, significantly latitudes and occasions when the jovian aurora was not prone to be energetic, may reveal indicators of dark matter annihilation across the large planet.

They discovered no detection of such a glow in Jupiter’s higher environment — nonetheless, like many “null outcomes” in science, this isn’t dangerous information. As a substitute, the researchers used their lack of a detection to calculate a most measurement for dark matter particles.

Placing a measurement restrict on dark matter

A number one principle of dark matter is that it made up of so-called weakly interacting huge particles, or WIMPS. Simply what the particles may very well be is closely disputed. The WIMP mannequin states that dark matter particles have some mass — versus particles with zero mass, like photons — and have to be in regards to the measurement of a proton.

These dark matter particles have to be flowing by way of all planets of the solar system on a regular basis, however often with out interacting.

Based on College of Chicago particle astrophysicist Dan Hooper, who wasn’t concerned within the examine, a back-of-the-envelope calculation means that as much as 2.2 kilos (1 kilogram) of dark matter is passing by way of Jupiter each second.

The planet’s intense gravity means a few of these particles should have fashioned an invisible cloud inside and round Jupiter that has constructed up over billions of years; and collisions between these invisible particles may create radiation. And in principle, that radiation would create an extra of H₃⁺  that may very well be detected as an infrared glow in Jupiter’s higher environment, Hooper says.

That glow is what the authors of the newest examine had hoped to detect.

However “when Cassini pointed it devices in direction of the night time aspect of Jupiter, it noticed precisely nothing,” says dark matter physicist Carlos Blanco of Princeton College, the examine’s lead writer.

Such an absence of detection — often known as a “null end result” in science — is akin to Sherlock Holmes fixing a thriller as a result of a canine didn’t bark.

Blanco and his co-author, astroparticle physicist Rebecca Leane at Stanford College, calculate that dark matter particles should have cross part lower than 10^-38 cm². In physics, the cross part of a particle is expounded to how seemingly it’s that the particle will work together with others. And if dark matter particles had been any bigger, they might work together extra usually and create a detectable sign.

That cross part is smaller than the dark matter dection experiments right here on Earth can spot, and the researchers say it reveals the worth of their strategy.

“The sort of detectors which you can put in a laboratory on Earth are actually solely delicate to dark matter particles which are heavier than hydrogen, and so they begin shedding sensitivity in a short time if the dark matter is lighter,” Blanco says. “What we found is that, basically, signatures that dark matter may go away on molecules like H₃⁺  is an efficient method of breaching that threshold and going to lighter and lighter particles.”

One step nearer

The null end result at Jupiter is just the start.

The authors counsel that the infrared glow created by collisions between dark matter particles may very well be simpler to detect within the atmospheres of exoplanets with extra mass than Jupiter, significantly in areas with extra dark matter — close to the middle of our galaxy, for instance.

“What you really need is one thing huge, like a ‘super-Jupiter’ [a planet more massive than Jupiter], that’s nearer to the galactic heart the place there’s a better focus of dark matter,” he says. “That method you’ll count on a better sign.”

At present, nonetheless, it isn’t doable to detect such glows from exoplanets, however Blanco hopes such know-how will quickly be developed. However he cautions that astronomers must enhance the sensitivity of the related devices by two or 3 times to be efficient.

“That’s a great distance off,” says cosmologist Joseph Silk of Johns Hopkins College, who wasn’t concerned within the examine.

Nonetheless, it’s yet another doable method that atstronomers could sometime see the unseeable and uncover the true nature of the mysterious dark matter that pervades our universe.