Two merging galaxies are locked in a cosmic death spiral similar to the one that will trap us in our corner of the Cosmos in a few billion years.

In about 5 billion years, our little corner of the Universe will look very different. Our Sun will turn into a red giant star, engulfing the inner Solar System.

Around the same time, in an unrelated process, the Milky Way will complete its merger with the nearby (and getting closer by the day) Andromeda galaxy. The violence of the merger will destroy the spiral structures of both galaxies, and the result will resemble the elliptical galaxy Messier 89 – a relatively featureless ball of aging low-mass stars and even older globular clusters.

Data collected by the Gemini North Telescope capture the early stages of another galactic spiral 60 million light-years away, involving the spiral galaxies NGC 4568 and NGC 4567.

Galaxies, stuck in a cosmic death spiral

The two galaxies are caught in each other’s gravitational pull. As they revolve around a common center of gravity, each pass brings them closer together. Right now, their galactic centers are about 20,000 light-years away—roughly the distance from Earth to the center of the Milky Way.

Each time the two galaxies pass each other, each galaxy’s gravity pulls long strings of stars, gas, and dust away from the other. Over the next 500 million years, this process will distort and smooth out the iconic spiral structure of the galaxies, leaving behind a simple spherical galaxy similar to Messier 89.

Astrophysicists base their prediction on observations of mergers like this one and elliptical galaxies like Messier 89, as well as computer models of the physics involved.

Like Messier 89, the post-merger giant galaxy will appear much older and less active than the two spiral galaxies that formed it. When galaxies merge, the stars don’t usually crash into each other. There is enough free space between the stars that the chances of such an accident are very small.

What is happening to these galaxies?

However, clouds of gas and dust between stars will collide, and the shock waves of these collisions will create areas where the gas is suddenly denser and hotter. These areas will explode in waves of star formation.

By the time the merger is complete, most of the gas and dust in both galaxies will be part of the stars formed during the collisions or will be blown away by the strong winds of the newborn stars.

Most of the remaining stars will be older and less massive, as most of the truly massive stars will have already lived out their short, energetic lives and met a violent end, he writes Inver.

The result sounds a little depressing: cold, dark and featureless compared to the active and complexly structured spiral galaxies that came before.

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