Astronomers on Earth can detect these starburst regions in their snapshots of galaxy mergers, such as this one, captured by the Hubble Space Telescope. The process would create hazy pockets of gas and dust in the night sky that eventually collapse under their own weight and ignite into brand-new stars. “Galaxies have huge clouds of gas and dust in them, and then when galaxies interact, those huge clouds of gas and dust will collide,” Jeyhan Kartaltepe, an astrophysicist at the Rochester Institute of Technology who studies galaxy formation, told me. (If your planet was too far out in the boondocks, however, you might be in trouble: The hustle can untether stars from the very edges of a galaxy and fling them out into the depths of intergalactic space.)Įven as the stars file neatly past one another, the space between them can get a bit chaotic. There will be more stars around, but space is still, well, spacious, and “most of these stars are not in danger of colliding with something else,” McTier said. That’s how stars move in galaxy mergers, passing one another as seamlessly as uniformed musicians gliding across the grass. “Have you ever watched a really good marching band, a performance where two groups walk through each other?” she asked me. The big ol’ galaxy hanging in the darkened sky would simply be a fact of your existence, just like there’s a cratered moon in ours.Įven more exciting, you could take in that view mostly unperturbed, because, despite the galactic jumble, the possibility of your sun smashing into another would be extremely unlikely, Moiya McTier, an astrophysicist and the author of The Milky Way: An Autobiography of Our Galaxy, told me. Here, at the outskirts, the other galaxy merging with your own would gleam in the darkness, bigger and brighter than any star. “The sky would be filled with newly formed stars, and we would be able to see warped streams of stars, gas, and dust stretching across the sky.” The view would be especially stunning if you lived along the outer edges of the galaxy, where the night sky would be less crowded with stars than at the busy galactic center. The nighttime view “would be quite spectacular,” Vicente Rodriguez-Gomez, an astronomer at the National Autonomous University of Mexico, told me. What might it be like to exist in the midst of a galactic merger? That means-if we could fantasize for just a bit-the NGC galaxies could be, to someone else, home. Consider that NGC 4568 and NGC 4567 are full of stars, and most stars, as we’ve learned from observations of our own galaxy, have planets. (Zoom into this shot from Gemini North and you’ll spot the afterglow of an exploding star.) Galactic collisions also provide great material for daydreams about extraterrestrial life far beyond Earth. But galaxy mergers have all of that and more. Sure, supernovas are cool, and so are collisions of black holes. Galaxy mergers are some of the most imagination-sparking events in the universe. For now, they almost look like a little paper heart. The two galaxies involved-NGC 4567 at top, and NGC 4568 at bottom-will swing around each other, jostling existing stars and sparking new ones, until everything coalesces in about 500 million years. The latest image in the catalog, shown at the top of this article and taken by the Gemini North telescope in Hawaii, captures the beginning of a merger in sparkling detail. By then, the only sign that a merger once occurred is a faint shimmer of stellar material around the orb. And at the end, when what remains is a messy sphere. In the thick of it, when gravity has begun to stretch them out of their original shapes. Early on, when the galaxies are clustered together, as if they’re convened for a very important space conference. Gravity nudges galaxies toward one another-sometimes two, sometimes more-until they meet, their contents whooshing and mixing, and the slow-moving chaos molds them all into one big galactic ball.Īstronomers have observed such events, known as mergers, in nearly every stage of the process. When it’s not ensuring the downward trajectory of your spilled coffee directly onto your shirt here on Earth, the invisible force is playing arts and crafts with cosmic matter: crushing gas and dust into radiant new stars, smoothing clumpy rock into spherical planets, and, my personal favorite, smushing entire galaxies together. Gravity can do some pretty astonishing things out there in the universe.
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