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

Ahead of the peak of the Perseid meteor shower, we're re-airing our first episode with host Regina G. Barber https://www.npr.org/people/1082526815/regina-g-barber. In it, Regina and planetary scientist Melissa Rice https://geology.wwu.edu/people/ricem5 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 Shower https://skyandtelescope.org/astronomy-press-releases/a-perfect-year-for-the-perseid-meteor-shower/ Interested in more stellar science in the news? Email us your question at [email protected] mailto:[email protected]. Support 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 http://plus.npr.org. See pcm.adswizz.com https://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 https://www.npr.org/about-npr/179878450/privacy-policy

• 0:00Speaker 00

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• 0:11Speaker 01

  Hey, short wavers. 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. OK, here's the episode.

• 0:29Speaker 02

  You're listening to Short Wave from NPR.

• 0:36Speaker 01

  Oh, I love that sound. That's the sound of wishing on shooting stars in 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.

• 0:50Speaker 02

  It's a video game. Does it need to be accurate?

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  I'm just saying, in the game, you're picking up pieces of gaseous star from the beach.

• 0:58Speaker 02

  True.

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  And I don't know about you, but I've never seen chunks of star just lying around.

• 1:04Speaker 02

  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?

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  I mean, you're not wrong, Emily.

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  Yeah.

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  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.

• 1:27Speaker 02

  So today, Short Wave asks the question, "Twinkle, twinkle, little shooting star, tell us what you actually are."

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  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 stars. But we'll talk about what they really are and all their varieties.

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  I'm your host, Emily Kwong.

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  And I'm scientist in residence Regina Barber.

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  And this is Short Wave, the daily science podcast from NPR.

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• 3:14Speaker 02

  OK, 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.

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  Yeah, so I brought my friend Melissa Rice. She's a planetary scientist.

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  Uh huh.

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  She works on Mars rovers.

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  So cool.

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  And I like to tell people she drives robots on another planet.

• 3:36Speaker 02

  That's a really cool job description.

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  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.

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  What is the difference?

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  Asteroids are strictly any planetary body, or like Hanka Rock from the asteroid.

• 3:53Speaker 02

  OK.

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  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.

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  And how many comets are there out there?

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  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.

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  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 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 gaseous phases.

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  I love it when comets come by Earth. It's a global science event, you know?

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  Yeah.

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  We have Halley'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's surface?

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  Melissa said, not many.

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  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 whether the impactor that hit 65 million years ago and was responsible for killing the dinosaurs, the Chicxulub impact, might have been from a comet.

• 5:45Speaker 02

  Wait, I thought what wiped out the dinosaurs was a meteor. You're telling me it's a comet?

• 5:50Speaker 01

  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.

• 5:57Speaker 02

  Oh.

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  Doesn't really matter whether it starts off as a comet or an asteroid.

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  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 pea, most of the time.

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  Wow, OK.

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  That is entering the top of the Earth's atmosphere.

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  So this, 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 space rock on fire?

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  Yeah, that's what we're seeing. We're seeing little bits of rock, like, burning through our atmosphere.

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  Cool.

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  But Emily, even cooler is that this pea-sized chunk of rock has been traveling through the cosmos since the solar system formed.

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  What?

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  And it really is traveling fast, shooting.

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  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.

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  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.

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  So the Earth is accumulating space rocks?

• 7:10Speaker 01

  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.

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  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.

• 7:28Speaker 02

  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?

• 7:36Speaker 01

  Yeah.

• 7:36Speaker 02

  Just, just rocks colliding?

• 7:38Speaker 01

  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.

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  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.

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  And the debate's been going on for a long time, like, all the way back to the early 1600s.

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  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're 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.

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  Yeah, they're pretty much everywhere. And 2/3 of the ones collected by researchers come from Antarctica because they're really obvious to spot on top of those giant sheets of ice.

• 8:34Speaker 02

  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?

• 8:42Speaker 01

  Well, first, rocks don't really come up from the bottom of the glacier. So if there's a rock lying on top of the ice, it's probably a meteorite.

• 8:49Speaker 02

  Sure.

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  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 smaller scale at home.

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  Oh, how?

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  You can find flecks 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.

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  Observatory, this is Bart Simpson. I see something in the sky at 4:12:8 and last number is 7.

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  Hey, what are you doing? Give me that phone.

• 9:23Speaker 06

  Congratulations, Bart. You've just discovered a comet.

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  In this episode, Bart detects a comet that starts hurling towards Springfield.

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  It's traveling towards the Earth. That's a meteoroid.

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  It's breaking up.

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  As soon as it hits the Earth's atmosphere and starts streaking through the sky, then it's a meteor.

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  And finally.

• 9:51Speaker 04

  When it hits the ground, it's a meteorite.

• 9:53Speaker 05

  Cool. We're saved.

• 9:58Speaker 01

  At the end there, Ward actually picks up the meteorite.

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  OK, you can't actually do that in real life, though, right?

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  I mean, I thought that as a kid, but Melissa says it's totally possible.

• 10:08Speaker 04

  Rocks are really poor conductors, and so it would actually be cold to the touch if you were to pick it up. Um, 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.

• 10:29Speaker 02

  Hmm. 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?

• 10:38Speaker 01

  Yeah, that was a bit terrifying, but she's OK. It landed on her pillow, and Melissa actually made me a little less anxious with some more news.

• 10:46Speaker 04

  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.

• 10:58Speaker 01

  OK. 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.

• 11:06Speaker 02

  OK.

• 11:07Speaker 01

  And it has been confirmed a farmer saw one hit and kill a dog.

• 11:09Speaker 02

  OK, yeah, you just snuck that in there. That's a sad detail. Uh.

• 11:14Speaker 01

  Yeah.

• 11:16Speaker 02

  Statistically speaking, though, it sounds like the odds are in our favor as far as meteorite fatalities.

• 11:21Speaker 01

  Yeah, there's one less thing to worry about not getting hit by a meteorite.

• 11:26Speaker 02

  Yeah, we ended this in a bright place.

• 11:28Speaker 01

  We did.

• 11:29Speaker 02

  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.

• 11:38Speaker 01

  Thank you.

• 11:46Speaker 02

  Today's episode was produced by Rebecca Ramirez and edited by Gisele Grayson, who is our senior supervising editor. Catherine Cypher checked the facts. Gillian Moon and Brian Jarboe were the audio engineers. Neil Karuth is our senior director of on-demand news programming, and our senior vice president of programming is Anya Grunman. I'm Emily Kwong.

• 12:07Speaker 01

  And I'm Regina Barber.

• 12:08Speaker 02

  And thank you so much for listening to Short Wave, the Daily Science Wish Cast from NPR.

• 12:25Speaker 02

  If you got one chance to wish on a shooting star and knew it would come true, what would you wish for?

• 12:30Speaker 01

  It's like a dinner with Michael Keaton, right?

• 12:35Speaker 02

  Let's put that out there, law of attraction.

• 12:37Speaker 01

  I can't believe I did put that out there. Anyway, Em, what would you wish for?

• 12:46Speaker 02

  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.

• 12:58Speaker 01

  It's gonna happen.

• 12:59Speaker 02

  Thank you.

• 13:00Speaker 01

  We're gonna wish on a star.

• 13:01Speaker 02

  OK, here we go. Ready?

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  which plan works for you.