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The spiral-shaped disc of stars and planets is being pulled, twisted and deformed with extreme violence by the gravitational force of a smaller galaxy: the Large Magellanic Cloud (LMC).
Scientists believe that the LMC crossed the Milky Way’s border about 700 million years ago – recent by cosmological standards – and due to its large dark matter content it greatly disrupted the texture and motion of our galaxy as it fell.
The effects are still visible today and should force a review of how our galaxy has evolved, astronomers say.
LMC, now a satellite galaxy of the Milky Way, is visible as a faint cloud in the southern hemisphere’s night skies, as observed by its namesake, 16th-century Portuguese explorer Ferdinand Magellan.
Previous research has revealed that the LMC, like the Milky Way, is surrounded by a halo of dark matter – elusive particles that surround galaxies and do not absorb or emit light but have dramatic gravitational effects on the movement of stars and gases in the universe.
Using a sophisticated statistical model that calculated the velocity of the most distant stars in the Milky Way, the University of Edinburgh team discovered how the LMC distorted the motion of our galaxy. The study, published in Nature Astronomy, was funded by the UK Science and Technology Facilities Council (STFC).
The researchers found that the enormous attraction of the LMC’s dark matter halo is pulling and twisting the Milky Way’s disk at 32 km / s or 115,200 km / h towards the constellation of Pegasus.
To their surprise they also found that the Milky Way was not moving towards the current position of the LMC, as previously thought, but towards a point in its past trajectory.
They believe this is due to the fact that the LMC, powered by its enormous gravitational force, is moving away from the Milky Way at an even greater speed of 370 km / s, about 1.3 million kilometers per hour.
Astronomers say it’s as if the Milky Way is trying to hit a fast-moving target, but not aiming very well.
This discovery will help scientists develop new modeling techniques that capture the strong dynamic interaction between the two galaxies.
The astronomers now intend to find out the direction from which the LMC first fell towards the Milky Way and the exact time it happened. This will reveal the amount and distribution of dark matter in the Milky Way and LMC in unprecedented detail.
Dr Michael Petersen, lead author and Postdoctoral Research Associate, School of Physics and Astronomy, said:
“Our discoveries require a new generation of models of the Milky Way to describe the evolution of our galaxy.
“We were able to show that stars at incredibly large distances, up to 300,000 light-years away, hold a memory of the Milky Way’s structure before the LMC fell and form a background against which we measured the stellar disk flying. in space, pulled by the gravitational force of the LMC. “
Professor Jorge Peñarrubia, personal president of gravitational dynamics, school of physics and astronomy, said:
“This discovery definitively breaks the spell that our galaxy is in some sort of state of equilibrium. In fact, the recent fall of the LMC is causing violent disruptions on the Milky Way.
“Understanding these can give us unprecedented insight into the distribution of dark matter in both galaxies.”
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