Using gravitational lensing, scientists have found that dark matter can extend over a million light-years from galactic centers, suggesting significant adjustments to our theories of gravity or the concept of dark matter itself. Source: SciTechDaily.com
Groundbreaking new research shows that the rotation curves of galaxies remain flat even at great distances and indefinitely, confirming the predictions of modified gravity theory as an alternative to dark matter.
This finding challenges existing models of cosmology and suggests that either the dark matter halos are enormously extensive or that our understanding of gravity theory needs a fundamental reassessment.
Breakthrough in cosmology
In a groundbreaking discovery that challenges the conventional understanding of cosmology, scientists at Case Western Reserve University have uncovered new evidence that could change our perception of the cosmos.
Tobias Mistele, a postdoctoral fellow in the Department of Astronomy in the College of Arts and Sciences at Case Western Reserve University, was the first to develop a revolutionary technique that uses gravitational lensing to penetrate the enigmatic realm of dark matter. He discovered that the rotation curves of galaxies remain flat across millions of light-years, with no end in sight.
Until now, scientists assumed that the rotation curves of galaxies must decrease the further one looks into space.
Modeling the weak lens rotation curve. Image credit: Case Western Reserve University
Questioning traditional cosmic models
The behavior of stars in galaxies has always puzzled astronomers. According to Newtonian gravity, stars at the outer edges should slower as the gravitational force decreases. This has not been observed, leading to the conclusion that it is dark matter. But dark matter halos should also end at some point, so rotation curves should not remain flat indefinitely.
Mistele’s analysis refutes this expectation and leads to a surprising revelation: the influence of so-called dark matter goes far beyond previous estimates and extends over at least a million light years from the galactic center.
Tobias Mistele. Photo credit: Case Western Reserve University
Such a long-range effect could indicate that dark matter – as we understand it – may not exist at all.
“This finding challenges existing models,” he said. “It suggests that either enormously extended dark matter halos exist or that we need to fundamentally rethink our understanding of gravity theory.”
Revolutionary implications for astrophysics
Stacy McGaugh, professor and director of the Department of Astronomy in the College of Arts and Sciences, said Mistele’s findings, which were published in the Astrophysical Journal Letterscross traditional boundaries.
“The significance of this discovery is profound,” McGaugh said. “Not only does it have the potential to redefine our understanding of dark matter, but it also encourages us to explore alternative theories of gravity, challenging the very framework of modern astrophysics.”
Einstein’s theory turned on its head
The main technique Mistele used in his research is gravitational lensing, a phenomenon predicted in Einstein’s general theory of relativity. Essentially, it occurs 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 happens because the mass of the object distorts the fabric of spacetime around it. This bending of light by galaxies persists over much larger scales than expected.
Stacy McGaugh. Photo credit: Case Western Reserve University
As part of his research, Mistele plotted the so-called Tully-Fisher relation to highlight the empirical relationship between the visible mass of a galaxy and its rotation speed.
“We knew this connection existed,” Mistele said. “But it wasn’t obvious that this connection would hold if you go further out. How long does this behavior last? That’s the question, because it can’t last forever.”
Mistele said his discovery underscores the need for further investigation and collaboration within the scientific community – and possible analysis of other data.
Reassessing theories of dark matter
McGaugh referred to the herculean – but so far unsuccessful – efforts of the international particle physics community to discover and identify dark matter particles.
“Either the dark matter halos are much larger than we expected, or the whole paradigm is wrong,” McGaugh said. “The theory that predicted this behavior in advance is the modified MOND theory of gravity, which Moti Milgrom proposed in 1983 as an alternative to dark matter. So the obvious and inevitably controversial interpretation of this result is that dark matter is a chimera; perhaps the evidence for this points to a new theory of gravity that goes beyond what Einstein taught us.”
Reference: “Indefinitely Flat Circular Velocities and the Baryonic Tully-Fisher Relation from Weak Lensing” by Tobias Mistele, Stacy McGaugh, Federico Lelli, James Schombert and Pengfei Li, Accepted, Astrophysical Journal Letters.
arXiv:2406.09685