The finest example is represented by the Sunflower galaxy (Messier 63 / NGC 5055) with the greatest external field amongst SPARC galaxies, whose well-measured rotation curve reveals a slightly decreasing habits at big radial range and can be precisely designed just with an external field result. Credit: ESA/Hubble & NASA
Team of global partners find ‘external field effect,’ a forecast distinct to MOND, competing dark matter hypothesis.
An global group of researchers, consisting of Case Western Reserve University Astronomy Chair Stacy McGaugh, has actually released research study competing that a competing concept to the popular dark matter hypothesis more precisely anticipates a stellar phenomenon that appears to defy the traditional guidelines of gravity.
This is considerable, the astrophysicists state, due to the fact that it even more develops the hypothesis — called customized Newtonian characteristics (MOND), or “modified gravity” — as a feasible description for a cosmological predicament: that galaxies appear to buck the long-accepted guidelines of gravity traced to Sir Isaac Newton in the late 1600’s.
The secret: For years, we’ve determined more gravitational pull in area than we believe we ought to have — that there’s insufficient noticeable or recognized matter to represent everything.
So, dark matter supporters think that the majority of the recognized universe is in fact made from product that doesn’t connect with light, making it unnoticeable and undetected — however that this product represent much of the gravitational pull amongst galaxies. It has actually been the dominating theory for almost 50 years.
MOND theory, a counter description presented by physicist Mordehai Milgrom from Weizmann Institute (Israel) in the early 1980s, states this gravitational pull exists due to the fact that the guidelines of gravity are somewhat changed.
Instead of associating the excess gravitational pull to a hidden, undetected dark matter, MOND recommends that gravity at low velocities is more powerful than would be anticipated by a pure Newtonian understanding.
In addition, MOND made a vibrant forecast: the internal movements of a things in the universes ought to not just depend upon the mass of the things itself, however likewise the gravitational pull from all other masses in deep space — called “the external field effect” (EFE).
Milgrom stated the findings, if robustly validated, would be “the smoking gun proving that galaxies are governed by modified dynamics rather than obeying the laws of Newton and of general relativity.”
150 galaxies checked for EFE
McGaugh and his partners, led by Kyu-Hyun Chae, from Sejong University in South Korea, state they found this EFE in more than 150 galaxies studied.
Their findings were released just recently in The Astrophysical Journal.
“The external field effect is a unique signature of MOND that does not occur in Newton-Einstein gravity,” McGaugh stated. “This has no analogy in conventional theory with dark matter. Detection of this effect is a real head-scratcher.”
The group of 6 astrophysicists and astronomers consists of lead author Chae and other factors from the United Kingdom, Italy and the United States.
“I have been working under the hypothesis that dark matter exists, so this result really surprised me,” Chae stated. “Initially, I was reluctant to interpret our own results in favor of MOND. But now I cannot deny the fact that the results as they stand clearly support MOND rather than the dark matter hypothesis.”
Analyzing turning galaxies
The group evaluated 153 rotation curves of disk galaxies as part of their research study. The galaxies were chosen from the Spitzer Photometry and Accurate Rotation Curves (SPARC) database, developed by another partner, Federico Lelli, throughout his postdoctoral research studies at Case Western Reserve, McGaugh and co-author James Schombert, of the University of Oregon.
In addition to Chae, McGaugh, Lelli and Schombert, the authors of the research study were Pengfei Li from Case Western Reserve and Harry Desmond from the University of Oxford.
The researchers stated they deduced the EFE by observing that galaxies in strong external fields slowed (or showed decreasing rotation curves) more regularly than galaxies in weaker external fields — as anticipated by MOND alone.
Lelli stated he was hesitant by the outcomes in the beginning “because the external field effect on rotation curves is expected to be very tiny. We spent months checking various systematics. In the end, it became clear we had a real, solid detection.”
McGaugh stated that uncertainty belongs to the clinical procedure and comprehends the hesitation of lots of researchers to think about MOND as a possibility.
“I came from the same place as those in dark matter community,” he stated. “It hurts to think that we could be so wrong. But Milgrom predicted this over 30 years ago with MOND. No other theory anticipated the observed behavior.”
Reference: “Testing the Strong Equivalence Principle: Detection of the External Field Effect in Rotationally Supported Galaxies” by Kyu-Hyun Chae, Federico Lelli, Harry Desmond, Stacy S. McGaugh, Pengfei Li and James M. Schombert, 20 November 2020, The Astrophysical Journal.
DOI: 10.3847/1538-4357/abbb96
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