The universe is full of puzzles, but few are as stubborn—or interesting—as dark matter. First proposed by astronomer Fritz Zwicki in 1933, this elusive substance refuses to play by the rules: it does not shine, absorb or interact with light in any way. In fact, we can’t see it at all. And yet, its invisible pull shapes the galaxy, hinting that there is something vast and mysterious.
Nearly 100 years later, and with the help of NASA’s Fermi Gamma-ray Space Telescope, researchers have finally “seen” dark matter for the first time.
If this proves to be true, it will be a significant development for science. Dark matter’s ability to hide in plain sight is legendary. It cannot be seen by any man-made instruments because dark matter cannot emit, absorb or reflect any kind of light, which is how humans and all our instruments see things. This makes finding dark matter impressively difficult.
University of Tokyo astronomy professor Tomonori Totani believes he may have succeeded where many before him have failed. In a research Published Nov. 25 in the Journal of Cosmology and Astroparticle Physics, Totani said he discovered dark matter by observing the byproducts of two dark matter particles colliding with each other.
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Key to this discovery is the theoretical existence of something called weakly interacting massive particles, or WIMPs for short. WIMPs are pieces of dark matter that are larger than protons and do not interact with any other type of particle. When two WIMPs collide with each other, scientific theory suggests that they annihilate each other, and the resulting reaction produces gamma rays.
Totani used data from NASA’s Fermi Gamma-ray Space Telescope to show what he believes are gamma-ray emissions from these destructive events, which, if accurate, would prove the existence of dark matter — or at least lead scientists on the right path to confirming its existence.
Why is dark matter so hard to find?
NASA describes Dark matter as “the invisible glue that holds the universe together.” Dark matter is everywhere. Theories suggest that only 5% of matter is ordinary stuff that you and I can see, while dark matter makes up 27%. The rest is dark energy, which Another mystery That science can still solve.
If there is five times more dark matter than regular matter, why is it so hard to see? The short answer is that dark matter does not interact with matter in a way that humans can detect with our current technology.
It is not completely unnatural. Science also has a hard time detecting black holes. Light cannot escape a black hole, so it is impossible to observe it directly. Instead, scientists have developed different methods to detect the presence of a black hole based on its effect on the surrounding environment.
Cygnus X-1 – the first black hole detected – was found thanks to something called an accretion disk. Accretion disks are swirling clouds of gas, dust, plasma, and other particles that form around black holes and emit large amounts of X-ray radiation. Researchers detected those intense X-rays and concluded that they came from a black hole. in The first image of a black hole Taken in 2019, the visible part is the black hole’s accretion disk, not the black hole itself.
English philosopher and clergyman John Michell first theorized the existence of black holes in 1783. That means it took mankind 236 years to photograph a black hole, and even then, we don’t see the black hole in the picture. We only know it’s there because we can see its accretion disk.
Detecting dark matter is much more challenging. It does not interact with the electromagnetic spectrum at all, including visible light. Much like a black hole, science has tried to prove its existence using its effect on its environment.
This phenomenon began in 1933, when the astronomer Fritz Zwicki observed that the galaxies in the Coma cluster were moving too fast for the amount of ordinary matter they contained. Zwicky concluded that there must be a second type of unseen object that is adding more gravitational force, acting as a kind of glue that holds the cluster together.
This theory has been refined over time, as additional evidence has emerged. an example Gravitational lensingwhich is a bending of light caused by gravity. Bullet clusters are the best example of this possible by dark matter, but this has yet to be conclusively proven.
The study author explains what he found
Over the decades, scientists have made various proposals Potential candidates What are dark matter particles actually for? One such theory is WIMP. These theoretical particles are much larger than photons and have a distinct characteristic. When they collide, science predicts that they will annihilate each other, resulting in a gamma ray burst.
NASA has Here is a short video This shows how it would work in theory. It is this gamma-ray emission that Totani believes he has found.
“We detected photon energy of 20 gigaelectronvolts (or 20 billion electronvolts, a huge amount of energy, gamma rays extending in a halolike structure toward the center of the Milky Way galaxy,” Totani Phys.org says. The gamma-ray emission component closely matches the shape expected from a dark matter halo.
There’s a bit to unpack here, so I asked Totani for more information. He told me that the stars in our galaxy are “distributed in a disk, while a halo of dark matter is thought to surround it spherically.” Radiation from theoretical dark matter would reach the disk from its spherical position, giving Totani an idea of what to look for and where to look in general.
Once he looked there, he was able to find radiation that he says is “consistent with predictions of dark matter.
To put it another way, the gamma rays were where they were supposed to be, at the photon energy levels that science predicted they would be, and the emissions were in the form expected for dark matter.
Changing science forever
Totani found the gamma rays where they were supposed to be and at the predicted energy, so it must be dark matter, right?
not right
While these results are promising, they do not necessarily prove the existence of dark matter. The first step would be for independent researchers to verify Totani’s conclusions.
Totani is aware of this and wants independent researchers to examine the data in an attempt to replicate his findings. This includes measuring gamma-ray emission from other sources, such as dwarf galaxies, to see if something else in the universe might explain his findings.
Currently, his findings are not easily explained by any known source of gamma ray emission, but that does not mean that none exists. The data needs to be checked and rechecked and researchers need to come up with more information to verify that his findings are indeed related to dark matter.
Science will take its time with this, because if Totani actually finds dark matter, the implications will be huge. He noted that the discovery of a new elementary particle not included in the current Standard Model of particle physics would have a significant impact on fundamental physics theory. And the discovery of dark matter will help piece together other cosmic mysteries, e.g The nature of dark energyThe invisible force that causes the universe to expand at an accelerating rate.
“If correct, the true nature of dark matter, long the greatest mystery of the cosmos, has been revealed,” Totani said.
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