Astronomers have found ‘cold’ dark matter — believed to make up a bulk of the universe’s mass– existing in much smaller clumps than was previously known or observed, according to an official press release by NASA. The observations are a big scientific breakthrough because finding dark matter in smaller clumps is considered especially difficult, given that dark matter is invisible.
The scientific breakthrough was possible with the help of NASA’s Hubble Space telescope and a new observing technique being deployed. The Hubble Space telescope was used to observe eight quasars and their foreground galaxies for the discovery. Quasars, also called cosmic streetlights, are regions around active black holes that emit enormous amounts of light.
It was here that dark matter in small clumps, in the range of 1/10,000th to 1/100,000th times to the mass of our Milky Way Galaxy’s dark matter halo was discovered. These quasars are located roughly 10 billion light-years from Earth; the foreground galaxies are about two billion light-years away from Earth.
The discovery of dark matter in such small clump appears to confirm some fundamental predictions of ‘cold dark matter’ theory, adds NASA. It also gives new insights into how this dark matter behaves. The term cold when used in context of dark matter refers to speed of the particles, and primarily dark matter is believed to be slow-moving, rather than fast-moving.
“Dark matter is colder than we knew at smaller scales. Astronomers have carried out other observational tests of dark matter theories before, but ours provides the strongest evidence yet for the presence of small clumps of cold dark matter. By combining the latest theoretical predictions, statistical tools and new Hubble observations, we now have a much more robust result than was previously possible,” Anna Nierenberg of NASA’s Jet Propulsion Laboratory in Pasadena, California, leader of the Hubble survey said in the press statement.
Dark Matter and Galaxy Formation
According to the theory, all galaxies have clouds of dark matter embedded in them. Dark Matter is an invisible form of matter, which constitutes a bulk of the universe’s mass and creates the scaffolding upon which galaxies are built, explains NASA.
It adds that Dark matter can come together to form structures, which is hundreds of thousands of times the mass of the Milky Way galaxy or to create small clumps. While dark matter cannot be seen, its presence is detected indirectly by measuring how its gravity affects stars and galaxies nearby. So when it exists in small clumps, the traditional method of observation fails.
In the Hubble technique, astronomers observed these eight quasars to discover the dark matter. These eight quasars and their foreground galaxies were aligned so precisely that the warping effect, also called gravitational lensing, produced four distorted images of each quasar.
According to NASA, “the dark matter clumps are located along the telescope’s line of sight to the quasars, as well as in and around the foreground lensing galaxies.” The presence of the dark matter concentrations alters the apparent brightness and position of each distorted quasar image, notes NASA.
The astronomers compared these measurements to how the quasar would look without the dark matter clumps. This was used to calculate masses of the tiny dark matter concentrations. Explaining how this works, team member Daniel Gilman of UCLA said, “Imagine that each one of these eight galaxies is a giant magnifying glass. Small dark matter clumps act as small cracks on the magnifying glass, altering the brightness and position of the four quasar images compared to what you would expect to see if the glass were smooth.”
Despite the new observations, dark matter remains a mystery for astronomers and scientists because it is yet to be observed in a lab