“Pull and twist” – Continuous contortions from the ancient collision of the Milky Way with the nearby dark matter Halo

The long-held belief that the Milky Way, which is home to Earth and our solar system, is relatively static has been dispelled. In a violent and dynamic dance between two galaxies, the dark matter halo of the Large Magellanic Cloud (LMC), a massive satellite galaxy one hundredth of the Milky Way, visible as a faint cloud in the southern hemisphere night skies – as observed from its namesake, 16th-century Portuguese explorer Ferdinand Magellan, is pulling and twisting the Milky Way’s spiral-shaped disk of stars and planets at 115,200 kilometers per hour toward the constellation Pegasus.

“This discovery definitely breaks the spell that our galaxy is in some sort of state of equilibrium. In fact, the recent fall of the CML is causing violent disturbances on the Milky Way, “said Jorge Peñarrubia, Personal Presidency of Gravitational Dynamics, University of Edinburgh School of Physics and Astronomy.” Understanding these can give us unprecedented insight. on the distribution of dark matter in both galaxies. “

Scientists believe that the LMC (image below) 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 movement of our galaxy. . The effects are still visible today and should force a review of how our galaxy has evolved, according to University of Edinburgh astronomers, who discovered to their surprise that the Milky Way was not moving towards the present. position of the LMC, as previously thought, but towards a point in its past trajectory.

Using a sophisticated statistical model, the Edinburgh team 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. They found 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.

2.7 billion years ago “Umbrellas of Stars”: a dwarf galaxy crashed along the coast of the Milky Way

An earlier 2007 study by the Harvard-Smithsonian Center for Astrophysics suggested that there are two possible explanations for these high speeds. One, that the Milky Way’s mass extension is greater than previously thought. If the LMC is gravitationally linked to the Milky Way, the Milky Way must be much more massive than previously suggested data. The excess mass would attract the LMC, keeping it “close at hand”. Two, that the LMC is gravitationally bound to the Milky Way. If the previous calculations of the Milky Way’s mass are accurate, then the Milky Way isn’t massive enough to hold onto its companions. In a few billion years it will escape from the Milky Way.

“It’s huge!” –Our Milky Way may be twice as large as previously thought

The LMC and its companion, Small Magellanic Cloud (SMC), may not be true Milky Way companions, but perhaps passing travelers into the neighborhood, astronomer Nitya Kallivayalil then with the Harvard-Smithsonian Center for Astrophysics suggested.

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, which will reveal the amount and distribution of dark matter in the Milky Way and LMC. with unprecedented detail.

“Our findings require a new generation of models of the Milky Way to describe the evolution of our galaxy,” said lead author Michael Petersen. “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. “

The first accurate 3D map of the Milky Way shown at the top of the page reveals its true shape: warped and twisted. Astronomers from Macquarie University and the Chinese Academy of Sciences used 1339 “standard” stars to map the true shape of our galaxy. Impression of the artist above the deformed and twisted disk of the Milky Way. (Chen Xiaodian)

The Daily Galaxy, Sam Cabot, via the University of Edinburgh

Image credits: LMC via Harvard CfA