Categories: galaxies

Galaxy Mergers can Boost Star Formation, and it can Also Shut it Down

Galaxy mergers are beautiful sights, but ultimately deadly. In the midst of the collision, the combined galaxy will shine brighter than it ever has before. But that glory comes with a price: all those new stars use up all the available fuel, and star formation grinds to a halt.

Our own galaxy, the Milky Way, will merge with our nearest neighbor, Andromeda, in about 4 billion years. And our galaxy is not alone: galaxies merge with each other across the universe, as evidenced by the plethora of galaxies caught in the act (so to speak) by our observations.

Teasing out the details of the merger process and its effects on the galaxies is difficult. We can’t watch a single galaxy merger event play out in real time, because the whole thing takes hundreds of millions of years to complete. But we can observe different stages of the process from the multitude of snapshots that we can see.

A recent study of a merged galaxy, known as ID2299, adds to the intricate portrait. As far as we can tell, when galaxies first merge it’s a glorious sight: the star formation ramps up from all the collisions of gas clouds and extreme gravitational interactions. Briefly, the merged galaxies can shine up to ten times brighter than they did individually.

But to make stars you need fuel in the form of reserves of cold gas. And unfortunately, the merger event heats up the galaxy in several ways. For one, the central supermassive black hole feeds on fresh rounds of material brought down to the core. That feeding event triggers the release of intense amounts of radiation which floods the surrounding galaxy. For another, all those new stars include tons of large, hot, bright stars, which also flood the galaxy with high-energy radiation, especially when they go supernova.

Taken together, the intense heat and the lack of raw materials suppress the formation of new stars, and the merged galaxy eventually settles into galactic retirement, fading from the cosmic stage.

At least it was fun while it lasted.

Paul M. Sutter

Astrophysicist, Author, Host | pmsutter.com

Recent Posts

Can We Survive in Space? It Might Depend on How Our Gut Microbiome Adapts

For over a century, people have dreamed of the day when humanity (as a species)…

10 hours ago

A New, More Accurate Measurement for the Clumpiness of the Universe

Cosmologists are wrestling with an interesting question: how much clumpiness does the Universe have? There…

15 hours ago

Scientists Track How a Giant Wave Moved Through Our Galactic Backyard

Astronomers say there's a wave rippling through our galactic neighborhood that's playing a part in…

1 day ago

JWST Sees a Milky Way-Like Galaxy Coming Together in the Early Universe

The gigantic galaxies we see in the Universe today, including our own Milky Way galaxy,…

1 day ago

The Brightest Object Ever Seen in the Universe

It's an exciting time in astronomy today, where records are being broken and reset regularly.…

1 day ago

Japan's New H3 Rocket Successfully Blasts Off

Japan successfully tested its new flagship H3 rocket after an earlier version failed last year.…

3 days ago