University of Waterloo, Ontario, researchers claim they have captured a composite image of the elusive substance, dark matter, that supposedly connects all galaxies that exist together in a cosmic web. Though there is reportedly five times more dark matter than normal matter in the universe, it has, so far, not been directly seen or detected. However, many astronomers believe it exists because of observations they have made on the gravitational effects the substance appears to exert on visible matter.
Some scientists think dark matter “explains why galaxies stick together.” Because the substance has proven to be so difficult to directly detect, though, other scientists have started to reassess the idea that dark matter is the reason for the “gravitational effect on luminous matter” they are seeing through their telescopes.
There have been at least a few scientists who have sought a different explanation for gravitational effects that astronomers have observed. These scientists, like University of Amsterdam physicist Erik Verlinde, have developed a differing theory of gravity. Their theory does not state that dark matter is needed to explain “the motion of stars in galaxies.”
Astronomer Margot Brouwer of Leiden Observatory in the Netherland led a team of researchers who tested the theory Verlinde had that dark matter was not needed to explain certain gravitational effects like “lensing.” The team analyzed the lensing effect of gravity that was influential and had been ascribed to dark matter in over 33,000 galaxies. They discovered that when free parameters are taken into consideration, the observations they made on the lensing effect of gravity on the galaxies that had been attribute previously to dark matter agrees with Verlinde’s theory. Free parameters are values that when adjusted make theory and observations match.
Brouwer said the model of dark matter that already exists and that the researchers at the University of Waterloo have taken into consideration in their attempts to detect dark matter fits better with the data than the prediction made by Verlinde. She said, though, that the prediction made by Verlinde does not rely on the explanation of free parameters, while the dark matter prediction does. When that is taken into consideration and is mathematically factored in, she said that Verlinde’s model is actually more accurate.
Despite the fact that some scientists are starting to doubt the existence of dark matter, astronomers who still believe that it is real and think it is responsible for how objects in the universe behave, have been heartened by the composite image of dark matter produced by Professor of Astronomy, Mike Hudson with the University of Waterloo and his colleagues. They believe that the image proves the existence dark matter.
Astronomers have been well aware of the lensing effect gravity has for some time now, and that light can be bent by bodies exerting gravitational force. According to UPI, smaller cosmic objects, like strands of dark matter, have enough gravity that they can bend light like “strands of dark matter.” A cosmic object does not necessarily have to be huge in order for it to have enough gravitational force to bend light.
Researchers involved with creating the composite image analyzed “23,000 galaxy pairs located 4.5 billion light-years away.” They did so with the aid of “the Canada-France-Hawaii Telescope.” The composite image of the galactic pairs showed that gravitational lensing was, indeed, occurring, though it was relatively weak. The composite image also revealed “the presence of dark matter filaments between the galaxies.”
Hudson definitely believes that the composite image offers evidence dark matter exists and is the substance that ties galaxies together. He stated that the composite image should be enough evidence dark matter exists for astronomers to progress “beyond predictions to something we can see and measure.” The co-author of the paper written about the composite image, and published “in the journal Monthly Notices of the Royal Astronomical Society,” was Seth Epps, a Waterloo grad student.
According to EarthSky, the Royal Astronomical Society said in an April 12, 2017 statement that the composite image confirmed “predictions that galaxies across the universe are tied together through a cosmic web connected by dark matter.” However, before astronomers accept that the composite image Mike Hudson and his colleagues created offers definite evidence that dark matter exists, the research needs to be replicated.
While the composite image created by Mike Hudson and his fellow researchers at the University of Waterloo in Ontario possibly depicts evidence that dark matter exists, other astronomers need to replicate the results before it is widely accepted that the image is proof the substance is real. Dark energy is thought to contribute 73 percent of all the mass and energy contained in the universe. Twenty-three percent of all matter is the universe is believed to be is dark matter. That leaves just four percent of the universe, which is composed of regular matter. People, planets and stars are a part of that tiny four percent.
By John Samuels
Photo Courtesy University of Waterloo