Scientists might have “seen” darkish matter for the primary time, due to NASA’s Fermi gamma-ray house telescope. If that’s the case, this is able to mark the primary direct detection of the universe’s most mysterious substance.
Darkish matter was theorized in 1933 by astronomer Fritz Zwicky, who discovered that the seen galaxies of the Coma Cluster lacked the required gravitational affect to stop this cluster from flying aside. Then, within the Seventies, astronomer Vera Rubin and colleagues discovered the outer edges of spiral galaxies had been spinning on the identical fee as their facilities, one thing that might solely be potential if the key quantity of mass in these galaxies wasn’t concentrated at their facilities, however fairly extra broadly dispersed. These aren’t direct observations of darkish matter, in fact, however inferences made utilizing darkish matter’s interactions with gravity in addition to the affect gravity then has on extraordinary matter and light-weight. Nonetheless, due to these findings, s astronomers have since calculated that each one giant galaxies are embedded inside huge haloes of darkish matter that increase means past the boundaries of seen matter in galaxies (equivalent to galactic haloes of stars).
The particles of this mysterious substance are actually estimated to outweigh the particles that make up on a regular basis matter by a ratio of 5 to at least one. Which means every thing we see round us on a day-to-day foundation — stars, planets, moons, our our bodies, subsequent door’s cat, and so forth — all account for simply 15% of the matter within the universe, with darkish matter accounting for the opposite 85%. Including to the thriller of darkish matter is the truth that, as a result of it interacts with electromagnetic radiation so weakly, or under no circumstances, it would not emit, soak up, or replicate gentle. Thus, it’s successfully invisible in all wavelengths of sunshine — or at the least, we thought it was.
There may be one chance that might end in darkish matter producing gentle. If darkish matter particles “annihilate” once they meet one another and work together, a lot as matter and its counterpart antimatter do, then it ought to produce a bathe of particles, together with photons of gamma-rays that, whereas invisible to our eyes, could possibly be “seen” by delicate gamma-ray house telescopes. One of many instructed “self-annihilating” particles theorized to comprise darkish matter are so-called “Weakly Interacting Large Particles” or “WIMPS.”
A team of researchers, led by Tomonori Totani from the Department of Astronomy at the University of Tokyo, trained the Fermi spacecraft on the regions of the Milky Way where dark matter should congregate, namely at the center of our galaxy, and hunted for this telltale gamma-ray signature.
Well, Totani thinks we finally found that signature.
“We detected gamma rays with a photon energy of 20 gigaelectronvolts (or 20 billion electronvolts, an extremely large amount of energy) extending in a halolike structure toward the center of the Milky Way galaxy,” Totani said. “The gamma-ray emission component closely matches the shape expected from the dark matter halo.”
And this isn’t the only close match. The energy signature of these gamma-rays closely matches those predicted to emerge from the annihilation of colliding WIMPs, which are predicted to have a mass around 500 times that of a proton, the ordinary matter particles found at the heart of atoms. Totani suggests there aren’t any other astronomical phenomena that easily explain the gamma-rays observed by Fermi.
“If this is correct, to the extent of my knowledge, it would mark the first time humanity has ‘seen’ dark matter. And it turns out that dark matter is a new particle not included in the current standard model of particle physics,” Totani said. “This signifies a major development in astronomy and physics.”
While Totani is confident that what he and his colleagues have detected is the signature of dark matter WIMPs annihilating each other at the heart of the Milky Way, the scientific community in general will require more hard evidence before the book is closed on this nearly century-old mystery.
“This may be achieved once more data is accumulated, and if so, it would provide even stronger evidence that the gamma rays originate from dark matter,” Totani added.
The team’s research was published on Tuesday (Nov. 25) in the Journal of Cosmology and Astroparticle Physics.
