Within the early Thirties, Swiss astronomer Fritz Zwicky seen that many galaxies had been transferring far sooner than their seen mass ought to allow. This uncommon movement led him to suggest that some form of invisible construction — darkish matter — was supplying the additional gravitational pull wanted to maintain these galaxies intact. Practically a century later, NASA’s Fermi Gamma-ray Area Telescope could have captured the primary direct proof of this mysterious substance, providing the potential for lastly “seeing” darkish matter.
Darkish matter has remained certainly one of astronomy’s largest unknowns because it was first advised. Till now, scientists have solely been in a position to examine it not directly by observing the way it impacts unusual matter, comparable to the way in which it produces sufficient gravity to carry galaxies collectively. Direct detection has not been potential as a result of darkish matter particles don’t work together with electromagnetic drive — which means they don’t take up, replicate or emit gentle.
The WIMP Speculation and Predicted Gamma Rays
Many researchers imagine that darkish matter is manufactured from weakly interacting large particles, or WIMPs. These particles are regarded as heavier than protons and work together so weakly with regular matter that they’re extraordinarily tough to detect. Nevertheless, idea means that when two WIMPs collide, they annihilate one another and launch energetic particles, together with gamma ray photons.
Scientists have spent years inspecting areas the place darkish matter must be concentrated, particularly the middle of the Milky Method, looking for these particular gamma rays. Utilizing new information from the Fermi Gamma-ray Area Telescope, Professor Tomonori Totani of the College of Tokyo now believes he has recognized the expected gamma ray sign related to darkish matter particle annihilation.
Totani’s findings seem within the Journal of Cosmology and Astroparticle Physics.
A 20-GeV Gamma Ray Halo Close to the Milky Method Heart
“We detected gamma rays with a photon power of 20 gigaelectronvolts (or 20 billion electronvolts, an especially great amount of power) extending in a halolike construction towards the middle of the Milky Method galaxy. The gamma-ray emission part intently matches the form anticipated from the darkish matter halo,” mentioned Totani.
The measured gamma ray power spectrum, which describes how the depth of the emission varies, intently matches mannequin predictions for the annihilation of hypothetical WIMPs with lots roughly 500 occasions that of a proton. The estimated frequency of those annihilation occasions based mostly on the noticed gamma ray depth additionally matches inside anticipated theoretical ranges.
Evaluating the Chance of a Main Breakthrough
Totani explains that the gamma ray sample can’t be simply matched to different recognized sources or extra frequent astrophysical processes. Due to this, he views the info as a robust candidate for long-sought gamma ray emission from darkish matter.
“If that is right, to the extent of my information, it might mark the primary time humanity has ‘seen’ darkish matter. And it seems that darkish matter is a brand new particle not included within the present customary mannequin of particle physics. This signifies a significant improvement in astronomy and physics,” mentioned Totani.
Subsequent Steps and Unbiased Verification
Though Totani is assured in his evaluation, he emphasizes that impartial affirmation is important. Different researchers might want to overview the info to confirm that the halolike radiation actually outcomes from darkish matter annihilation fairly than one other astrophysical supply.
Additional assist might come from discovering the identical gamma ray signature in different areas wealthy in darkish matter. Dwarf galaxies orbiting inside the Milky Method halo are thought-about particularly promising. “This can be achieved as soon as extra information is amassed, and in that case, it might present even stronger proof that the gamma rays originate from darkish matter,” mentioned Totani.
Funding: This work was supported by JSPS/MEXT KAKENHI Grant Quantity 18K03692.
