Researchers Discover a Gigantic Ring of Galaxies That Could Bring Einstein’s Gravity into Question*
By Alexa Erickson
Einstein’s theory of gravity explains gravity as a distortion of space that’s caused by the presence of matter or energy. This has long been considered the genius that changed science’s perception of gravity. However, researchers at the University of St Andrews may be giving Einstein a run for his money, having found a gigantic ring of galaxies darting away from us much quicker than predicted.
The 10 million light year-wide ring is made up of small galaxies that are expanding rapidly like a mini Big Bang. According to the researchers, at some point in time our neighbouring galaxy, Andromeda, flew past our own galaxy at close range, sling-shotting off several small galaxies in the process.
“If Einstein’s Gravity were correct, our Galaxy would never come close enough to Andromeda to scatter anything that fast,” explains one of the team, Hongsheng Zhao from the University of St Andrews in Scotland.
The discovery, if proven correct, would create a whole new understanding of gravity and our cosmos, considering a galactic flyby is only plausible if, as galaxies move away from one another, gravity weakens more slowly than Einstein’s theory suggests.
“The ring-like distribution is very peculiar. These small galaxies are like a string of raindrops flung out from a spinning umbrella. I found there is barely a 1 in 640 chance for randomly distributed galaxies to line up in the observed way. I traced their origin to a dynamical event when the Universe was only half its present age,” says Indranil Banik, the PhD student who led the study.
“The high galactocentric radial velocities (GRVs) of some Local Group galaxies must have been caused by forces acting on them that our model does not account for,” the researchers say in their paper.
Furthermore, these galaxies exist on the same plane of the Universe as the Milky Way and the Andromeda Galaxy, which the researchers argue is unlikely to be a coincidence.
The tsunami-like wake in the sky, then, was likely the result of a near-miss of the speeding Andromeda galaxy with the Milky Way. Orbiting each other in a plane, the the two galaxies would have pushed aside dwarf galaxies in their trails. This may reveal why the speeding dwarfs are in a plane with the Milky Way and Andromeda.
“In Einstein’s gravity paradigm, hypothetical dark matter is always invoked. Such a high speed requires 60 times the mass we see in the stars of the Milky Way and Andromeda. However, the friction between their huge halos of dark matter would result in them merging rather than flying 2.5 million light years apart, as they must have done.,” Banik says.
Though we’ll have to see where this study leads, the possibilities it opens up for theoretical physics are exciting.
“Science progresses through challenges,” says Marcel Pawlowski, a Hubble Fellow at the University of California, Irvine, who elicited Banik’s discovery.
“Together with two other known planes of closer-in satellites, this gigantic ring forms a serious challenge to the standard paradigm.”