Astronomers witness galaxies collide like a bullet and a target

Eric Hopton for redOrbit.com – Your Universe Online

Look out Earthlings. Your time here is nearly over.

In four billion years, a mere blink of an eye by universal standards, planet Earth will be part of a galactic collision when our Milky Way will smash into the Andromeda spiral galaxy. By then global warming and who gets to be President won’t matter much, but it should be some spectacle. It’s a shame Pink Floyd won’t be around to do the light show.

Astronomers from the European Space Agency’s XMM-Newton X-Ray Telescope caught a glimpse into what this future collision might look like on Wednesday. During the REFLEX II survey of 900 galaxy clusters, observers were lucky enough to spot a distant galaxy, almost 1.5 billion light-years away, impact another group of galaxies like a bullet. As the bullet entered its target, gas was ripped away in a spectacular event.

The “bullet galaxy” weighed 200 trillion times the mass of the Earth and penetrated the main cluster, known as Abell 4067, at 814 miles per second. The core of the bullet component survived the impact, leaving stripped gas behind at the centre of the main cluster.

A report on the observations will be published in the journal Astronomy and Astrophysics by its main authors, Gayoung Chon and Hans Boehringer from of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany.

The discovery of the merging cluster, RXCJ2359.3-6042, reveals a unique system. Chon and Boehringer report that, “The bullet goes right through the central region of the cluster without being disrupted and we can clearly watch the process how the bullet component is stripped of its layers outside the core. Spearheading the bullet is a cool core centred by a massive early type galaxy.”

National Geographic points out the importance of witnessing such events. Data from galactic collisions helps scientists understand the process and can tell us how much these distant galaxies might weigh. The observations from the Abell 4067 “bullet” should tell us more about the physics involved in the impacts as well as how much gas surrounds the ancient, compact galaxy.

The after-effects of the collision produced a massive shock wave from which the scientists hope to pick up invaluable images.

As for our galaxy’s own impending collisions with Andromeda go, currently the two systems are speeding towards each other at about 250,000 miles an hour. But, they’re still 2.5 million light-years apart, so no need to cancel the newspapers just yet.  You have a four-billion-year cushion to get things sorted.

When they do finally collide, though, the two systems will enter a long term state of change and evolution as they continually come together and separate again. It may take a billion years for the two galaxies to finally merge into one.

A team of astronomers based at the Space Telescope Science Institute has studied the potential Milky Way-Andromeda event and produced an animation of how they see the collision happening and the formation of the new “Milkomeda” galactic system. (And it’s freakin’ awesome!!!)

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