Short Wave - Shooting stars are just pea-sized rocks... and other space wonders

Episode Date: August 5, 2026

Ahead of the peak of the Perseid meteor shower, we're re-airing our first episode with host Regina G. Barber. In it, Regina and planetary scientist Melissa Rice explore all things shooting stars. They talk about the different types, where they come from and what they actually are (hint: not stars).Learn more about viewing the Perseids, which will peak Aug. 12: A Perfect Year for the Perseid Meteor ShowerInterested in more stellar science in the news? Email us your question at [e-mail] public media with NPR+ and enjoy perks for over 25 podcasts like this one. It includes perks like bonus episodes, early access, archive access, curated playlists and sponsor-free listening. Learn more at plus.npr.org. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Hey, Shortwavers, Regina Barber here, and today is my birthday. And I have just one wish for you to follow us on the NPR app or on your go-to podcast app. Never miss an episode like the one you're about to hear from my early days on the pod. Okay, here's the episode. You're listening to Shortwave from NPR. I love that sound. That's the sound of wishing on shooting stars and Animal Crossing, which I played a lot of at the beginning of the pandemic. But sadly, Emily, putting on my scientist in residence hat, the star falling sound, it's not super accurate.

It's a video game. Does it need to be accurate? I'm just saying, in the game, you're picking up pieces of gaseous star from the beach. True. And I don't know about you, but I've never seen chunks of star just lying around. Well, that's because you are a real scientist, Regina Barber. I imagine when you were a kid and gazed into the night sky, you asked technical things of the cosmos. Like, what are you made of chemically? I mean, you're not wrong, Emily.

I wanted to know what a meteor was. You know, I didn't take it at face value as a little kid that they were actually stars falling from the sky. And the truth of what they are is much cooler. So today's shortwave asks the question. Twinkle, twinkle, little shooting star. Tell us what you actually are. I brought my friend and NASA team member, Melissa Rice,

to tell us what exactly we're putting our hopes and dreams on, which many of you know are not exactly. exactly stars, but we'll talk about what they really are and all their varieties. I'm your host, Emily Kwong. And I'm scientists in residence, Regina Barber. And this is Shortwave, the Daily Science Podcast from NPR. Okay, Regina, so through your powerful connections as an astrophysicist, you managed to get us an interview with a real-life NASA scientist to help us understand the true meaning of shooting

stars. Yeah, so I brought my friend Melissa Rice. She's a planetary scientist. She works on Mars rovers. So cool. And I like to tell people she drives robots on another planet. That's a really cool job description. Yes, I agree.

And she told me that first of all, there's a couple of types of space rocks out in the universe orbiting our sun. There's asteroids and there's comets. What is the difference? Asteroids are strictly any planetary body or like hunker rock from the asteroid. Okay. Comets, on the other hand, they're made up of ice and dust. They're basically big, dirty snowballs. But astronomers have been observing them for like thousands of years.

And how many comets are there out there? NASA says there's about 4,000 like known comets. But there's probably way more orbiting the sun beyond Neptune and the Kuiper Belt. We just don't notice them because they're kind of just hanging out and orbiting. But Melissa says, every once in a while, one of them gets a nudge. Maybe the gravity of Jupiter is like, hey, I'm going to yank you this way. Or maybe something hits one of them and they get knocked into the, the inner solar system. And so that's why we see comets not that often, but when we see them,

we see them with these beautiful tails, this long streak behind them. And that's the icy parts that are coming close enough to the sun that they're turning from solid into gas-shift phases. I love it when comets come by Earth. It's a global science event. You know, we have Haley's comet. And then in the northern hemisphere, we get the treat of seeing the Perseid shower every August. But how many of those bits of space rock make it down here to the earth surface? Melissa said, not many. Whatever's left of them is probably not going to make it down to the surface and last that long. But the rocky fragments, those are pieces that we can probably find. And comets will certainly leave impact craters. There is some debate about. There is some debate

about whether the impactor that hit 65 million years ago and was responsible for killing the dinosaurs, that Chicksilup impact might have been from a comet. Wait, I thought what wiped out the dinosaurs was a meteor. You're telling me it's a comet? Right. So a meteor is more of a general term. It's what happens if an asteroid or a comet is falling through the Earth's atmosphere. It doesn't really matter whether it starts off as a comet or an asteroid.

The most common thing we're looking at when we see that bright streak across the sky is a little piece of rock, probably no bigger than a pee, most of the time. Wow. Okay. That is entering the top of the Earth's atmosphere. So this little piece of rock no bigger than a pea, is that kind of what a shooting star is? It's just a little piece of rock on fire? Yeah, that's what we're seeing. We're seeing little bits of rock like burning through our atmosphere. Cool.

But Emily, even cooler is that this pea-sized chunk. chunk of rock has been traveling through the cosmos since the solar system formed. What? And it really is traveling fast. Shooting. That part of the phrase is right. As it's traveling so fast through the atmosphere, it's encountering a lot of friction, it's bumping into all those atmospheric molecules, and it's heating up.

And most of those shooting stars never make it to the ground. They burn up entirely in the atmosphere. And so they're adding to our atmosphere. It's the Earth. continuing to grow as a planet. So the Earth is accumulating space rocks? Yeah, the atmosphere is growing in mass, and our solar system is always changing. That's how the planet's formed by accumulating space rocks and continuing to grow.

I mean, that's what the Earth is, is a bunch of space rocks that hit each other and grew bigger and bigger to form our planet. Wow. This is kind of blowing my mind. Like, it's making me reconsider what a planet is. Is this how the Earth was made? Yeah. Just rocks colliding? Yeah, mass attracts mass.

But it's really just the last few decades that researchers reached a broad consensus that rocks fall from space. Before then, people didn't even know how the craters on the moon were formed. That was contentious until the 1960s, the Apollo program. There was serious scientific debate about whether the holes in the ground on the moon were volcanoes or impact craters. And the debate's been going on for a long time, like all the way back to the early 1600s. That is a long time to be debating this. At least now we've established that the craters on the moon and the craters on the earth are real. They are from space rocks.

And we can still find remnants of these space rocks that have collided with Earth here, right? There's traces. There's evidence that that happened. Yeah, they're pretty much everywhere. And two-thirds of the ones collected by researchers come from Antarctica, because they're really obvious to spot on top of those giant sheets of ice. That makes sense, yeah. But how do you know that the thing you're picking up is a meteorite, that it came from space,

and it's not just some random rock? Well, first, rocks don't really come up from the bottom of the glacier. So if there's a rock line on top of the ice, it's probably a meteorite. Sure. Second, researchers can use powerful magnets to detect some of them, especially the ones that are made up of mostly iron, which actually you and I can do on a much small. scale at home. Oh, how? You can find flex of space on your roof or on your deck using a pretty

powerful magnet. You know, that actually reminds me of a Simpsons episode that shows the journey of one of these space rocks landing on Earth. Observatory, this is Bart Simpson. I see something in the sky at 412, 8 and last number of 7. Hey, what are you doing? Give me that phone. Congratulations, Bart. You've just discovered a comet. In this episode, Bart detects a comet that starts hurling towards springfield. It's traveling towards the earth. That's a meteoroid.

Look! It's breaking up! As soon as it hits the Earth's atmosphere and starts streaking through the sky, then it's a meteor. And finally, when it hits the ground, it's a meteorite. Cool. At the end there, Bart actually picks up The meteorite. Okay. You can't actually do that in real life, though. Right? I mean, I thought that as a kid, but Melissa says it's totally possible.

Rocks are really poor conductors. And so it would actually be cold to the touch if you were to pick it up. Most of the evidence that we have is anecdotal from the limited number of people who have seen a fall and then gone and touched it. And so we need more data as always. I mean, gathering more data is a bit precarious. I mean, wasn't there the story about a woman in British Columbia who had a meteorite fall through her house? Yeah, that was a bit terrifying, but she's okay. It landed on her pillow. And Melissa actually made me a little less anxious with some more news.

It's disturbing to think that rocks could fall from space, but there haven't been any recorded fatalities of a human being by a meteorite impact. Okay. Researchers might have found evidence of a death in Iraq, like back in the 1800s. And Melissa says there has been a few close calls. Okay. And it has been confirmed a farmer saw one hit and kill a dog. Okay. Yeah, you just snuck that in there.

That's a sad detail. Yeah. Statistically speaking, though, it sounds like the odds are in our favor as far as meteorite fatalities. Yeah. There's one less thing to worry about not getting hit by a meteorite. You know, we ended this in a bright place. I'm glad for that. And I appreciate you giving me so much wish-related wisdom.

I will think about you when I wish upon a star the next time. Thank you. Today's episode was produced by Rebecca Ramirez and edited by Giselle Grayson, who is our senior supervising editor. Catherine Seifer checked the facts. Gilly Moon and Brian Jarbo were the audio engineers. Neil Carruth is our senior director of On-demand news programming, and our senior vice president of programming is Ony.

Grunman. I'm Emily Kwong. And I'm Regina Barber. And thank you so much for listening to Shortwave, the Daily Science Wishcast from NPR. If you got one chance to wish on a shooting star and knew it would come true, what would you wish for? It's like a dinner with Michael Keaton, right? Let's put that out there. Law of attraction. I can't believe I did put that out there anyway. M., what would you wish for? I would want to have a no-holds-barred conversation with Michelle Kwan.

maybe a little bit of ice skating, but I think the only reason I'm a journalist is because it brings me ever closer to the possibility of interviewing her. It's going to happen. Thank you. We're going to wish on a star. Okay, here we go. Ready?