From Durham University: “Milky Way heading for catastrophic collision”

Durham U bloc

From Durham University

4 January 2019

Hubble Space Telescope image representing a merger between two galaxies (M51a and M51b) similar in mass to the Milky Way and the Large Magellanic Cloud. Credit: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team (STScI/AURA)

Milky Way NASA/JPL-Caltech /ESO R. Hurt

Large Magellanic Cloud by by German astrophotographer Eckhard Slawik

There’s an enemy in our midst. Quietly circling around our galaxy, it could send our Solar System hurtling out of the Milky Way and into the obscurity of interstellar space.

Its name is the Large Magellanic Cloud (LMC), and even though it is one of the more researched satellite galaxies buzzing around our own, astrophysicists are only now seeing it for what it truly is: an unusually large cosmic threat.

The Milky Way is on a collision course with a neighbouring galaxy that could fling our Solar System into space.

The Large Magellanic Cloud could hit our galaxy in two billion years’ time.

On the off chance that humans survive for another two billion years, our descendants will be in for a treat.

If the catastrophic collision wakes up the black hole sleeping at the center of our galaxy, this dark beast will begin devouring everything in sight, growing ten times larger than it already is.

As it feeds on surrounding gas, the stage will be set and the show will begin – what the researchers describe as a “spectacular display of cosmic fireworks.”

“This phenomenon will generate powerful jets of high energy radiation emanating from just outside the black hole,” explains lead author Marius Cautun, a cosmologist at Durham University.

“While this will not affect our Solar System, there is a small chance that we might not escape unscathed from the collision between the two galaxies which could knock us out of the Milky Way and into interstellar space.”

Our galaxy is long overdue for such a collision. So far, it has managed to get by relatively unscathed in the grand scheme of things. Especially when you consider the company that it keeps.

The Milky Way is surrounded by a group of smaller satellite galaxies, orbiting quietly around us.

These galaxies can lead separate lives for many billions of years, but on occasion, they can find themselves sinking into the centre of their host galaxy, until at last they collide and are swallowed up completely.

In this way, galaxies are constantly evolving and growing, but the Milky Way’s poor appetite makes it quite atypical.

In comparison to our own galaxy, for instance, Andromeda can devour galaxies weighing nearly 30 times more.

“We think that up to now our galaxy has had only a few mergers with very low mass galaxies,” says co-author Alis Deason, a computational cosmologist at Durham University.

“This represents very slim pickings when compared to nearby galaxies of the same size as the Milky Way.”

This galactic collision would happen much sooner than the predicted impact between the Milky Way and another neighbour, Andromeda, which scientists say will hit our galaxy in eight billion years.

Andromeda Galaxy Adam Evans

Active black hole

The coming together with the Large Magellanic Cloud could wake up our galaxy’s dormant black hole, which would begin devouring surrounding gas and increase in size by up to ten times.

SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

Sgr A* from ESO VLT

As it feeds, the now-active black hole would throw out high-energy radiation.

While these cosmic fireworks are unlikely to affect life on Earth, researchers say there is a small chance that the initial collision could send our Solar System hurtling into space.

Dark matter

The Large Magellanic Cloud is the Milky Way’s brightest satellite galaxy and only entered our neighbourhood about 1.5 billion years ago. It sits about 163,000 light years from our galaxy.

Until recently, astronomers thought that it would either orbit the Milky Way for many billions of years, or, since it moves so fast, escape from our galaxy’s gravitational pull.

However, recent measurements indicate that the Large Magellanic Cloud has nearly twice as much dark matter than previously thought.

Solar System

Researchers say that since it has a larger than expected mass, the Large Magellanic Cloud is rapidly losing energy and is doomed to collide with our galaxy, which could have consequences for our Solar System.

Lead researcher Dr Marius Cautun, a postdoctoral fellow in our Institute for Computational Cosmology, said: “There is a small chance that we might not escape unscathed from the collision between the two galaxies, which could knock us out of the Milky Way and into space.”

Read the full research paper MNRAS.

See the full article here .


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