The universe is full of mysteries, but few are as persistent – or as fascinating – as dark matter. First proposed by astronomer Fritz Zwicky in 1933, this elusive substance refuses to follow the rules: it does not glow, absorb light, or interact with light in any way. In fact, we can’t see it at all. But their invisible pull forms galaxies, suggesting that something big (and mysterious) is out there.
After nearly 100 years, and with the help of NASA’s Fermi gamma-ray space telescope, scientists may have finally “seen” dark matter for the first time.
If true, this would represent a significant advance for science. Dark matter’s ability to hide in plain sight is legendary. It cannot be seen by any instrument ever made by man because dark matter cannot emit, absorb or reflect any light, the same way humans and all our instruments see things. This makes the search for dark matter incredibly difficult.
Tomonori Totani, a professor of astronomy at the University of Tokyo, believes he has succeeded where many others before him failed. IN a study According to Totani, published Nov. 25 in the Journal of Cosmology and Astroparticle Physics, he could have discovered dark matter by observing the byproduct of the collision between two dark matter particles.
The key to this discovery lies in the theoretical existence of so-called weakly interacting massive particles (WIMPs). WIMPs are bits of dark matter that are larger than protons and do not interact with other types of particles. When two WIMPs collide, scientific theory suggests that they will destroy each other and the resulting reaction will produce gamma rays.
Totani used data from NASA’s Fermi Gamma-ray Space Telescope to determine what he believes to be gamma rays emanating from these destruction events. If true, it would prove the existence of dark matter, or at least put scientists on the 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 matter that you and I can see, while dark matter makes up 27% of the pie. The rest is dark energy. another mystery Science has not yet solved this problem.
If there is five times more dark matter than normal matter, why is it so hard to detect? The short answer is: dark matter does not interact with matter in a way that humans can detect with our current technology.
It’s not completely unnatural. Even science has difficulty detecting black holes. Light cannot escape from a black hole, so it is impossible to observe it directly. Instead, scientists have developed several methods to detect the existence of a black hole based on its impact on the environment.
Cygnus X-1, the first black hole ever discovered, was discovered with something called an accretion disk. Accretion discs are swirling clouds of gas, dust, plasma and other particles that form around black holes and tend to emit large amounts of X-rays. Scientists detected these intense X-rays and concluded that they came from a black hole. In there first image of a black hole In the 2019 image, the visible part is the black hole’s accretion disk, not the black hole itself.
The English philosopher and preacher John Michell first proposed the theory of the existence of black holes in 1783. This means that it took humanity 236 years to take a picture of a black hole, and even then we cannot see the black hole in the picture. We only know it’s there because we can see the accretion disk.
Dark matter is much harder to detect. It does not interact at all with the electromagnetic spectrum, including visible light. Like black holes, science has used their effects on the environment to prove their existence.
This phenomenon began in 1933 when the astronomer Fritz Zwicky noticed that the Coma cluster galaxies were moving too fast compared to the amount of ordinary matter they contained. Zwicky concluded that there must be a second type of invisible matter that exerted a stronger gravitational pull and acted as a kind of glue that held the cluster together.
This theory has been refined over time and more evidence has emerged. An example is the gravitational lensing effectThis is the diffraction of light caused by gravity. The Bullet Cluster is the best example that this could be due to dark matter, but it has not yet been conclusively proven.
The author of the study explains what he found.
In recent decades, researchers have proposed several potential candidates what dark matter particles really are. One of these theories is WIMP. These theoretical particles are much larger than photons and have a special property. When they collide, science predicts that they will destroy each other and create a gamma ray burst.
NASA has a short video here This shows how it would work in theory. Totani believes he has found these gamma rays.
“We detected gamma rays with a photon energy of 20 giga-electron volts (or 20 billion electron volts, an enormous amount of energy) propagating in a halo-like structure toward the center of the Milky Way,” Totani said. Phys.org said. “The gamma-ray component closely matches the predicted shape of the dark matter halo.”
There’s some unpacking to be done here, so I reached out to Totani for more information. He told me that the stars in our Milky Way “are distributed in a disc, while the halo of dark matter probably surrounds them in a spherical shape.” Radiation produced by the theoretical dark matter would enter the disc from its spherical position, giving Totani an idea of what and where to look in general.
When he looked there, he was able to find radiation that he said was “consistent with predictions of dark matter.”
In other words, the gamma rays were where they should be, at the photon energy level predicted by science, and the emissions were in the form expected for dark matter.
Changing science forever
Totani found gamma rays where they should be and with expected intensity, so it must be dark matter, right?
Not quite.
While these results are promising, they do not necessarily prove the existence of dark matter. The first step will be for independent researchers to verify Totani’s results.
Totani is aware of this and wants independent researchers to examine the data to try to replicate his findings. This means measuring gamma rays from other sources, such as dwarf galaxies, in the universe to see if something else can explain their results.
At present, their findings cannot be easily explained by known sources of gamma rays, but that does not mean they are not there. The data must be tested again and again, and scientists must provide more information to verify whether their findings are indeed linked to dark matter.
Science will take its time, because if Totani really discovered dark matter, the impact would be enormous. He notes that the discovery of a new elementary particle that is not part of the current Standard Model of particle physics will have important implications for the fundamental theory of physics. And the discovery of dark matter would help solve other cosmological mysteries like this one. The nature of dark energythe invisible force that causes the universe to expand faster.
“If true, this would reveal the true nature of dark matter, the biggest mystery in cosmology for a long time,” Totani said.