Podcaster: Avivah Yamani
Title: Space Stories: Galaxies Don’t Crash, They Remix
Organization: Planetary Science Institute; langitselatan
Link : http://langitselatan.com
Description: Today podcast tell a story about galaxies collision and how gravity reshapes galaxies, builds tidal tails, and triggers starbursts.
Bio: Avivah Yamani is a an astronomy communicator from Indonesia and Project Manager of 365 Days of Astronomy.
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Transcript:
Hi, welcome to 365 Days of Astronomy. I’m Avivah, your host. Today we’re taking a slow-motion trip across billions of years to watch two giants meet face to face: galaxies on a collision course.
Spoiler alert: that includes our own Milky Way and our neighbor Andromeda, set to meet in about 4.5 billion years.
Should we freak out? Short answer: not at all. Here’s the long answer—and it’s way cooler.
Imagine two glittering cities of stars gliding toward each other in the dark. It’s easy to picture a cosmic pileup—stars smashing, sparks flying like fireworks. But space is mostly empty. The distances between stars are so huge that, even in a head-on meeting, almost all stars just slide past one another without touching.
How empty is “empty”? Let’s shrink it. The Sun is about 1.4 million km across. The nearest star, Proxima Centauri, is 4.24 light-years away—roughly 40 trillion km. If the Sun were a tennis ball in Miami, the nearest star would be another tennis ball in Seattle—about 4,300 km (2,700 miles) away. Or think Los Angeles to New York—around 3,900 km (2,450 miles). That’s how spread out stars are in a normal part of a galaxy.
So when galaxies meet, it’s not a demolition derby. It’s more like two swarms of bees flying through each other—each bee rarely gets close to another. But that doesn’t mean nothing happens.
When two galaxies pass through each other, their gravity gently tugs on the stars and changes their routes. Some stars get stretched into long, thin streams called tidal tails; others drift onto wider, more oval paths. Give those tiny nudges hundreds of millions of years, and both galaxies start to change shape. Two graceful spirals can bend and twist, then settle down as one bigger galaxy. If they’re similar in size and merge slowly, the end result can be a smoother, rounder elliptical galaxy.
Quick picture: think of two swirls of glitter sliding together—first you see streaks, and in the end you get one bigger, smoother swirl.
Now, here’s what does crash: gas and dust.
Unlike stars, big clouds of gas and dust do bump into each other. They pile up and compress, sending shock waves through the space between stars. That squeeze can kick off a baby-star boom—sometimes up to 100 times the usual star-making rate. We call these bursts of activity starbursts. On cosmic clocks, they’re short: in just a few million years, a galaxy can burn through much of its gas. It’s like tossing fuel on a fire—bright, dramatic, and brief.
What happens after the meet-up? It depends on who’s colliding.
If two galaxies are about the same size, astronomers call it a major merger. You don’t get destruction—you get transformation: one new, larger galaxy. If a big galaxy runs into a much smaller one, the big one can tear apart the little one and keep the pieces. That’s galactic cannibalism. Our Milky Way has done this many times—and it’s doing it right now with a few tiny companion galaxies.
Back to our original question: what about Andromeda and the Milky Way?
The answer is epic and reassuring. Over hundreds of millions of years, our galaxies will pass through each other more than once, pulling out starry streams, sparking new star formation, and slowly settling into a single, larger galaxy—sometimes nicknamed “Milkdromeda.” Through it all, the odds that our Sun actually hits another star are incredibly small. Earth will not be knocked into space by a direct hit.
Could our Solar System’s path change? Possibly—but slowly. The Sun may end up on a new orbit around the merged galaxy. And the night sky—if anyone’s around to see it—will be spectacular: great arcs of starlight, long ribbons of glowing gas, and a bright center where the two galaxies finally calm down.
So, the next time you see an image of two galaxies tangled together, remember: you’re looking at creation through collision. Not destruction, but a remix. Gravity is the choreographer, gas and dust are the drama, and stars are the dancers who mostly avoid bumping shoulders as the grand ballet unfolds.
That’s it for today’s trip through colliding galaxies—why stars rarely crash, how gas and dust ignite starbursts, and how these encounters reshape galaxies and write new chapters in cosmic evolution. Thanks for listening—and keep looking up!
End of podcast:
365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by Planetary Science Institute. Audio post production by me, Richard Drumm, project management by Avivah Yamani, and hosting donated by libsyn.com. This content is released under a creative commons Attribution-NonCommercial 4.0 International license. Please share what you love but don’t sell what’s free.
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As we wrap up today’s episode, we are looking forward to unravel more stories from the Universe. With every new discovery from ground-based and space-based observatories, and each milestone in space exploration, we come closer to understanding the cosmos and our place within it.
Until next time let the stars guide your curiosity