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In a discovery that challenges the conventional understanding of cosmology, Case Western Reserve University scientists have discovered new evidence that could change our perception of the cosmos.

Tobias Mistele, a postdoctoral fellow in the Department of Astronomy at Case Western Reserve’s College of Arts and Sciences, is pioneering a revolutionary technique that uses “gravitational lensing” to delve into the enigmatic realm of dark matter. He found that the rotation curves of galaxies remain flat for millions of light-years with no end in sight.

The work has been published on the preprint server arXiv.

Scientists previously believed that the rotation curves of galaxies should decrease the farther you look into space.

Traditionally, the behavior of stars in galaxies has puzzled astronomers. According to Newtonian gravity, stars at the outer edges should be slower due to the reduced gravitational pull. This was not observed, leading to the inference of dark matter. But even dark matter halos must disappear, so rotation curves must not remain flat indefinitely.

Mistele’s analysis defies this expectation, providing a startling revelation: the influence of what we call dark matter extends far beyond previous estimates, extending at least a million light-years from the galactic center.

Such a long-range effect could indicate that dark matter – as we understand it – may not exist at all.

“This discovery challenges existing models,” he said, “suggesting that either significantly extended dark matter halos exist or that we need to fundamentally reevaluate our understanding of gravitational theory.”

Stacy McGaw, professor and director of the Department of Astronomy in the College of Arts and Sciences, said Mistele’s findings, scheduled for publication in Astrophysical Journal Lettersexpand traditional boundaries.

“The implications of this finding are profound,” McGaw said. “Not only could this redefine our understanding of dark matter, but it also invites us to explore alternative theories of gravity, challenging the very fabric of modern astrophysics.”

Turning Einstein’s theory upside down

The main technique Mistele used in his research, gravitational lensing, is a phenomenon predicted by Einstein’s theory of general relativity. Essentially, this happens when a massive object, such as a galaxy cluster or even a single massive star, bends the path of light coming from a distant source. This bending of light occurs because the object’s mass distorts the fabric of spacetime around it. This bending of light by galaxies continues on much larger scales than expected.

As part of the study, Mistele plotted what is called the Tully-Fisher relation on a diagram to highlight the empirical relationship between a galaxy’s apparent mass and its rotation rate.

“We knew that connection existed,” Mistele said. “But it wasn’t obvious that the relationship would stick the more you dated. How far does this behavior go? That’s the point, because it can’t go on forever.”

Mistele said his discovery underscores the need for further research and collaboration within the scientific community — and the possible analysis of other data.

McGaw noted the Herculean — but so far unsuccessful — efforts in the international particle physics community to detect and identify dark matter particles.

“Either dark matter halos are much larger than we expected, or the whole paradigm is wrong,” McGough said.

“The theory that predicted this behavior beforehand was the modified MOND theory of gravity, hypothesized by Moti Milgrom as an alternative to dark matter in 1983. So, the obvious and inevitably controversial interpretation of this result is that dark matter is a chimera; perhaps the evidence as it points to some new theory of gravity beyond what Einstein taught us.”