Meeting with galaxy violently disrupted Milky Way, study finds

The spiral-shaped disc of the stars and planets is pulled, twisted and distorted with extreme violence by the gravitational force of a smaller galaxy – the Large Magellanic Cloud (LMC).

Scientists believe that LMC crossed the border into the Milky Way around 700 million years ago – recent by cosmological standards – and that due to its high dark matter content, it strongly disrupted the tissue and the movement of our galaxy during its fall.

The effects are still visible today and should force a review of how our galaxy evolved, astronomers say.

The LMC, now a satellite galaxy of the Milky Way, can be seen as a faint cloud in the southern hemisphere night sky – as observed by its namesake, 16th century Portuguese explorer Ferdinand Magellan.

Previous research has found that CML, like the Milky Way, is surrounded by a halo of dark matter – elusive particles that surround galaxies and neither absorb nor emit light but have dramatic gravitational effects on movement. stars and gases in the universe.

Using a sophisticated statistical model that calculated the velocity of stars farthest from 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 dark matter halo of the LMC pulls and twists the Milky Way’s disc at 32 km / s or 115,200 km / hour towards the constellation Pegasus.

To their surprise, they also found that the Milky Way was not moving to the current location of the LMC, as previously thought, but to a point in its past trajectory.

They believe this is because the LMC, powered by its massive gravitational force, is moving away from the Milky Way at the even faster speed of 370 km / s, or about 1.3 million km / hour.

Astronomers say it’s as if the Milky Way is trying hard 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.

Astronomers now intend to find out the direction from which the LMC first entered the Milky Way and the exact time that this happened. This will reveal the amount and distribution of dark matter in the Milky Way and CML in unprecedented detail.

Dr Michael Petersen, senior author and postdoctoral research associate, School of Physics and Astronomy, said: “Our findings involve 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, retain a memory of the structure of the Milky Way before the LMC fell and form a backdrop against which we measured the stellar disk flying in space pulled by the gravitational force of the LMC. “

Professor Jorge Peñarrubia, Personal Chair of Gravitational Dynamics, School of Physics and Astronomy, said: “This discovery definitely breaks the spell that our galaxy is in some kind of equilibrium state. In fact, the recent infestation of the LMC is causing violent disruption on the Milky Way.

“Understanding this can give us unprecedented insight into the distribution of dark matter in the two galaxies.”