One of the most mysterious components of the universe — dark matter — may have finally been found after a century-long search.
Dark matter emits no light or energy, so it is undetectable using telescopes. Scientists using data from NASA’s Fermi Gamma-Ray Space Telescope, which has been orbiting Earth since 2008, have detected the aftermath of dark matter particles colliding. Although stronger evidence is required, it could be a breakthrough in particle physics.
What Is Dark Matter?
Dark matter is thought to account for about 85% of matter in the universe and is thought to interact only with gravity. It’s therefore hypothetical; its existence is only inferred by its effect on other things.
Its existence was first proposed in 1933 by Swiss-American astronomer Fritz Zwicky, who observed that the galaxies in the Coma Cluster were behaving as if they had many hundreds of times more mass than they had. He explained it by postulating the existence of invisible particles that exert a gravitational force.
The particles that make up dark matter are invisible and absorb, reflect or emit no light or energy, according to NASA, so it’s impossible to detect directly — until now, perhaps.
Direct Detection Of Dark Matter
A new study published in the Journal of Cosmology and Astroparticle Physics, led by Professor Tomonori Totani from the University of Tokyo, reports the detection of gamma rays matching theoretical predictions for dark matter particle interactions. “If this is correct, to the extent of my knowledge, it would mark the first time humanity has ‘seen’ dark matter,” said Totani.
One leading theory suggests that dark matter consists of weakly interacting massive particles, WIMPs. A key prediction of this theory is that when two WIMPs collide, they annihilate and emit gamma-ray photons with very specific energies. Some scientists have therefore focused their efforts on finding evidence of those gamma-ray photons.
NASA’s Fermi Gamma-ray Space Telescope has been looking for evidence of just that in the center of the Milky Way, where dark matter is believed to be concentrated. Totani’s research focused on this region and identified the gamma-ray photons that theoretical models predict would result from “WIMP annihilation.”
“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,” said Totani. “The gamma-ray emission component closely matches the shape expected from the dark matter halo.”
Further Evidence Required
Despite the promising data, caution is warranted. As well as undergoing independent verification, scientists will require further evidence from other dark matter-rich regions. One key test would be to find gamma-ray signatures similar to those in dwarf galaxies, which also host high concentrations of dark matter.
“It turns out that dark matter is a new particle not included in the current standard model of particle physics,” said Totani. “This signifies a major development in astronomy and physics.”
Gamma rays are the most energetic form of light. Launched in 2008, the NASA’s Fermi space observatory helps scientists to research everything from the leftovers of stars and spinning pulsar stars to the origin of cosmic rays and gamma-ray bursts.
Wishing you clear skies and wide eyes.