Study finds flat rotation curves of galaxies over vast distances

In a groundbreaking discovery, scientists at Case Western Reserve University have uncovered new evidence that could fundamentally reshape our understanding of the . Tobias Mistele, a post-doctoral scholar in the Department of Astronomy at Case Western Reserve's College of Arts and Sciences, has utilized a novel approach involving “gravitational lensing” to explore the elusive realm of dark matter, revealing that the rotation curves of galaxies remain flat over millions of light-years, defying previous astronomical models.

Unprecedented Findings in Galactic Behavior

Mistele's findings, now available on the pre-print server arXiv, challenge the long-standing belief that the rotation curves of galaxies decline as one observes further into space. Traditionally, Newtonian physics suggested that at the periphery of galaxies should orbit more slowly due to reduced gravitational pull. This inconsistency with observed data led to the postulation of dark matter, which was thought to account for the unseen affecting galactic rotation.

However, even the dark matter posited that the effects would taper off eventually. Contrary to this expectation, Mistele's analysis reveals that the gravitational influence—attributed to dark matter—extends well beyond previous estimates, reaching at least a million light-years from the galactic center.

Implications for Dark Matter and Gravity

“This finding challenges existing models,” Mistele stated, “suggesting there exist either vastly extended dark matter halos or that we need to fundamentally reevaluate our understanding of gravitational theory.”

Stacy McGaugh, professor and director of the Department of Astronomy in the College of Arts and Sciences, emphasized the significance of these findings, which are set to be published in the Astrophysical Journal Letters. “The implications of this discovery are profound,” McGaugh noted. “It not only could redefine our understanding of dark matter but also beckons us to explore alternative theories of gravity, challenging the very fabric of modern .”

Gravitational Lensing and the Tully-Fisher Relation

Mistele's primary technique, gravitational lensing, leverages a predicted by Einstein's . This occurs when a massive object, such as a , bends the light from a distant source due to the warping of spacetime. The persistence of this light bending over much larger scales than anticipated has provided new insights into galactic dynamics.

In his research, Mistele also examined the Tully-Fisher relation, which describes the correlation between the visible mass of a and its rotation speed. “We knew this relationship existed,” Mistele explained. “But it wasn't obvious that the relationship would hold the farther you go out. How far does this behavior persist? That's the question, because it can't persist forever.”

The Future of Cosmological Research

Mistele's discovery underscores the need for further and collaboration within the scientific community. This includes the potential re-examination of existing data to better understand the implications of these findings.

McGaugh highlighted the ongoing challenges faced by the international particle physics community in detecting and identifying dark matter particles. “Either dark matter halos are much bigger than we expected, or the whole paradigm is wrong,” he said.

One alternative to the dark matter hypothesis is the Modified Newtonian Dynamics (MOND) theory, proposed by Moti Milgrom in 1983. This theory suggests a modification of gravity itself to account for the observed galactic behaviors without invoking dark matter. “The theory that predicted this behavior in advance is MOND,” McGaugh pointed out. “The controversial interpretation of this result is that dark matter is a chimera; perhaps the evidence for it is pointing to some new theory of gravity beyond what Einstein taught us.”

Source: Case Western Reserve University