Every now and then we look up and see bright fiery balls falling from the sky. Don’t panic, these are just bolides. Sometimes they leave trails, sometimes they explode, and sometimes they survive all the way to the ground.
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Female Announcer: This episode of Astronomy Cast, is brought to you by Swinburne Astronomy Online, the world’s longest running online astronomy degree program. Visit astonomy.swin.edu.au, for more information.
Fraser Cain: Astronomy Cast episode 416, Fireballs from Space. Welcome to Astronomy Cast, you’re weekly fact-based journey through the cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, I’m the publisher of Universe Today and with me is Dr. Pamela Gay, a professor at Southern Illinois University-Edwardsville and the director of Cosmos Quest. Hey Pamela, how ya doing?
Dr. Pamela Gay: I’m doing well, how are you doing Fraser?
Fraser Cain: I’m doing great, so I just got back from New Mexico. I got a chance to speak at the Bandolier National Monument, which is just outside of Santa Fe. It was unbelievable, it was so awesome. A big thanks to the folks at Bandolier for having me. Unfortunately, we had terrible weather, it was – there was a lightning storm and the rangers had these portable lightning detectors. And they were like, that one’s six miles away, that one’s three miles away. Okay everybody, we got to move inside and they had this beautiful telescope set up and they got rained on.
And so, we couldn’t have worse weather, but I had a wonderful time visiting and we had a sort of cool show. I gave a cool show for a small group of people anyway, and it was a lot fun, so let’s get on with the show. Hi everyone, Fraser here, once again, we just want to thank Casper Mattress for sponsoring Astronomy Cast, they’ve been sponsoring us for more than a year now and we really appreciate their support. I use Casper Mattress, I’ve got two of them here in the house and I’ve gone through the whole cycle. I’ve gone through hot summer, I’ve gone through cold winter and I still enjoy using the Casper Mattress all year long.
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Fraser Cain: Every now and then, we look up and see bright fiery balls falling from the sky, don’t panic, these are just fireballs. Sometimes they leave trails, sometimes they explode and sometimes they survive all the way to the ground. Pamela, have you ever seen a fireball?
Dr. Pamela Gay: I total have, back in – it was 1998, November, there was this amazing meteor shower and that year for whatever reason, there were way more fireballs and bolides than normal. And there was a whole group of us from the University of Texas-Austin, we went out to Bee Cave’s observatory and we were lined up like sardines in a can trying to keep warm as we lay on the concrete. And the meteorites, as they streaked across the sky, were getting several times brighter than Venus and casting shadows in some cases and a fair number of them, just actually exploded at the end of their passage.
Fraser Cain: Yeah, I’ve seen only one and it was – it wasn’t that long ago, it was probably four years ago. When I was out with the kids and we were out stargazing and we saw the sort of – around us, like it was like as if a flare went off. Like, it was very bright and it was like the full moon was suddenly out. And you – we all turned really quickly and we could see this really bright fireball going through the sky and I think I heard a sound, but I’m not sure. Sometimes you can hear sounds, so anyway. It was just an absolutely stunning experience and I – the only way to see it, I guess, spend more time outside. What did I see?
Dr. Pamela Gay: Well, what you saw was a small chunk of something, could have been space debris, could have been cometary debris, could have been asteroid debris and as it passed through our atmosphere, a couple of different things happened. First of all, it got hot and so, that’s glowy thing. And in some cases, where you see a lasting glowing tail behind your fireball, in that case, it is ionized a chunk of the atmosphere above 80 kilometers. So high up in the atmosphere, its ionizing particles as its passing through leaving a bright, glowy tail behind it.
And sometimes, they get so critically hot and either vapor pressure builds up inside or something happens that causes this sudden, tremendous burst of energy at the end. Where you see this flash of death light and in that special case, we have a bolide fireball.
Fraser Cain: Now you mentioned like a bunch of things that could cause it, right? Like it can be something from space, but it could also be debris that human beings have put up into space. So what is this sort of – what is the underlying object? How big are we looking at, when you see one of these things, you know, before it hits the atmosphere?
Dr. Pamela Gay: Well, the really cool thing about stuff like this, so first of all, just some definitions. Anytime you have something streaking through the atmosphere, that’s a shooting star, a meteor, call it what you will, it’s a small piece to a large piece of stuff. Now if that streak that you see going across the sky is several times brighter than Venus, then what you’re looking at and technically we say it’s magnitude minus four visual or brighter. In that case, you’re looking at a fireball and if that thing that you’re looking at, streaks across the sky and then explodes at the last second, in that case, what you’re looking at is a bolide.
Now, it could be any kind of stuff, but what makes it that fireball is how much energy it’s able to release and this energy can come from two different things. You either have a fairly big object and by big, I mean you might have a piece of gravel, how exciting, or bigger. Or, you can something smaller, but with a huge velocity relative to our atmosphere. The thing that always surprises me is just how different the velocity of different things hitting our atmosphere can be because it’s either something that’s just like kind of sneaking up on the Earth, not going that much of a different velocity than us. Or it can be something where it has an orbit the opposite of the Earths around the Sun and a head on collision occurs. So in some cases, it can be 25,000 miles performance hour, in other cases it can be over 100,000 performance hour.
Fraser Cain: Now man, one of those situations where lots of questions are coming together all at the same time, so let’s get back to sort of categorization because I think one of the big problems with this whole thing is that everything has got so many names. It is like a person from Vancouver Islands name for rain. So when it’s a big ball of rock, out in space that is an asteroid.
Dr. Pamela Gay: Yes, when it is a frozen body out in space that is more volatile than rock, it is a comet and there are objects where people argue if it’s a comet or a rock based on does it have a tail or not if you put it next to the Sun.
Fraser Cain: A com-steroid. An aster-omet. So okay, so those – that’s when it’s out is space, now if it’s really teeny tiny and it’s moving very quickly, it is a meteoroid, right?
Dr. Pamela Gay: If it’s passing through – so, yes. A little, tiny thing –
Fraser Cain: The windscreen of the International Space Station.
Dr. Pamela Gay: So a little, tiny thing that is a debris bit from an asteroid is a meteorite, yes.
Fraser Cain: Okay great, so little guy pass – smashing into the windscreen of the International Space Station, that’s a meteoroid?
Dr. Pamela Gay: Yes.
Fraser Cain: Okay, when that little thing passes into the atmosphere, lights up and glows, that is a meteor.
Dr. Pamela Gay: Yes.
Fraser Cain: And when that thing reaches the ground, it is a meteorite.
Dr. Pamela Gay: Yes.
Fraser Cain: If that thing is very bright, more than four magnitude minus four Venus, then it is a fireball.
Dr. Pamela Gay: Yes.
Fraser Cain: If that fireball explodes, it is a bolide.
Dr. Pamela Gay: Yes.
Fraser Cain: But if it reaches the group, we’re back to a meteorite.
Dr. Pamela Gay: Yes.
Fraser Cain: If that thing smashes into the ground and explodes and kills all the dinosaurs, it is still a meteorite.
Dr. Pamela Gay: Yes.
Fraser Cain: Okay, we got our definitions down. Now we talked a bit sizes, right, and the – not even people – don’t even realize is that meteors are – they’re the size of a piece of sand.
Dr. Pamela Gay: Yeah, most of the time, there are exceptions. We do occasionally, for instance, there was the discovery last week that King Tut had a dagger in his tomb that was made out of carved meteorite, which I find amazing. Which means the meteorite that they used was at least dagger sized. So we do get larger meteorites striking the surface of the planets. We tend to go to places that are constantly eroding the surface that allow them to pop out and be seen more easily when you want to collect them.
So people go to Antarctica and in the summer when the top layer melts off of the ice, walk around a nice shiny surface. Pick up the dark stuff, the dark stuff is generally meteorites. We also often can find in the sand dunes, where you have blowing sands in deserts, you can also find meteorites a little bit more easily than walking through the woods. But the kind of incredible thing is there’s like order of a thousand fireballs every, single night on the planet Earth. Or every, single 24 hour period on the planet Earth.
Fraser Cain: yeah, it’s terrifying how much of this stuff is actually raining down and how many of the – even Chelyabinsk Scale of explosions in the sky, there are something like one a year, on every couple of years. I mean it’s pretty amazing how much – how often these things are happening.
Dr. Pamela Gay: And the more detectors we build, the more security cameras we have pointed more up than down, the more we realize this stuff is constantly happening. We didn’t notice it a lot in the past because two thirds of the planet surface is water. Human beings down take up the whole surface of the planet, yet. We have vast swaths of desert, we have vast swaths of woods that have low population and for the most part, human beings try to sleep at night and aren’t outside looking up. So it’s really, really easy for all of these things to go entirely undetected. And so, we’re still learning how often potentially hitting the surface of the planet things are hitting our atmosphere.
Fraser Cain: Well, let’s talk about colors because part of the show with them is sort of bright color that you see and sometimes like usually the bright white, but you can get other colors. So when that piece of space stuff impacts the atmosphere, what is actually going on to make it bright? And then, I’d love to talk about why you get some of those colors from some of the bigger ones.
Dr. Pamela Gay: So initially, if it’s not that bright, if you’re dealing just like with your standard meteor passing through the atmosphere, as its passing through you will perceive white. And this is because the parts of our eyes that can detect low light, some like a light – no light and our brain goes, white, black, shades of grey. And occasionally, our brain will fill in colors that it knows, but that’s not because we’re detecting the colors, it’s because our brain is smart.
Now, as that meteor shooting through the sky becomes a brighter and brighter meteor, the light starts to be able to trigger the parts of our eye that detect color. The three different color detecting cells, for if you happen to be tetra-chromyl, and so, with these bright ones, we start receiving color. And there’s a lot of different people, perceive different things. Colors of all kinds have been seen and when it’s true color, it’s due totally to chemistry and occasionally, simply our brain making stuff up.
Fraser Cain: Right, you know what’s funny, this is sort of like a – I’m gonna go down a rabbit hole for a second here. Which is that whenever there is a fireball that happens, especially I find – I like to watch for them on Twitter and usually you’ll get this sort of cascade of messages being posted on Twitter when people are actually seeing them. And you will almost right away, someone will post a picture of – someone will post a fake picture of some of the nicest fireballs that have ever been seen, but they were completely predicted because they were reentering spacecraft that we knew were going to happen. I always see the same kinds of picture, so I have to go on to Twitter and go that’s fake, that’s fake. But yeah, if you’re lucky enough to know when some of these spacecraft are going to be returning to Earth, and you’re in the flight path, you’ll get a chance to watch it. Unless, it’s really large, like Meer or when the International Space Station finally comes down, you don’t want to be anywhere near it.
Dr. Pamela Gay: True, but we do get a fairly good show with the Perce, it’s in August, the Leonid’s in November, especially in the year’s right after the comets have refreshed their trails and we’re going through that nice, fresh trail. In this case, it’s icy volatile debris, but some of it is big enough to cause these amazing fireballs and bolides, like I saw back in ’98. So there is plenty of opportunity for there to be just regular, old go out on an August summer night, wear all of your bug spray, all of it, then add some more. And set up a camera and you can catch these things.
Fraser Cain: Yeah, absolutely. So you just mentioned a bit about the comets refreshing them, so can you go into a little more detail on this? I mean, is there fireball seasons in the way that we have meteor showers?
Dr. Pamela Gay: So what was kind of amazing was back at the beginning of the last century, there was actually one meteor shower that was so amazingly prolific that – and it was when the Earth went through, right after the tail of a comet went by. So like, comet goes by, comet lights up the sky, just a little bit later, Earth goes through that trail. And it was causing some reports of daytime observations, it was consider to actually be raining shooting stars.
Fraser Cain: There’s pictures, yeah, like in the 60s, just these amazing pictures of just like – yeah, hundreds of thousands of meteors performance hour. And I guess a ton of them would have been those really bright ones. The biggest one that I can remember was the 2001 Leonid’s, I think we’ve mentioned that a few times in the past. You know, everyone said, it’s gonna be a good meteor shower and I went outside and it absolutely was the most stunning meteor shower that I’ve ever seen. It was just – it was amazing, there was a meteor every couple of seconds, just zip, zip.
Dr. Pamela Gay: So the meteor shower that I was just referring to, it – the song that inspired is. “The Stars Fell on Alabama”, which was recorded in 1934, the meteor shower itself, occurred in early 1800s in 1833. It was the Leonid Meteor Shower. And so, it was considered the night the stars fell and it led to this jazz standard being produced.
Fraser Cain: So let’s talk a bit about what your job is when you see a fireball in the sky.
Dr. Pamela Gay: So – well, a lot of –
Fraser Cain: Like, first, obliviously tell everyone around you, wow, do you see that? Oh my god, yeah, if you happen to have your camera out and you’re taking a long duration photograph, then by all means, don’t kick your camera over because you’re gonna get a really amazing picture. Once that’s all done though, you have a job. You’ve been deputized.
Dr. Pamela Gay: It’s true, so the American Meteorological Society actually collects data on this, so if you go to amsmeteors.org, they have a form, because there’s always a form. They have a form that you can fill out to report seeing these fireballs. And so, there’re folks out there that – well, first of all, how far was the meteor seen, what time was it seen in different locations and this information, especially if you have a dash cam or some other thing that just happened to catch it and have a timestamp.
Security cameras are another way that we catch these things, it can allow us to track down, and by us I mean folks like Geoff Notkin and the other meteor hunters out there, to go out and find these fresh samples from space. And there’s actually a whole lot of science to be found in these rocks that had a rather terrible existence.
Fraser Cain: All right, well, let’s talk about the science then because as you said, sometimes they explode and actually survive and reach the ground. What goes into sort of finding them and what’s important there?
Dr. Pamela Gay: So we’ve two different situations that we’re looking at. First of all, you have things like Chelyabinsk, where that suckers explodes before it hits the ground. That was one heck of a fireball and bullet. Now in this case, you actually end up with shrapnel, kind of scattered all about and that shrapnel, each piece of shrapnel is a chance to understand our early solar system a little bit better. Now, even better than shrapnel, is those times when you get a larger chunk that makes it all the way to the surface of the planet. Because those larger chunks have the potential to have pockets of volatiles insides of them. Pockets of ice that turns to gas, stuff that – well, gets at what is the ratio of different types of oxygen. What is the ratio of different types of carbon in this gas that was trapped when the rock formed, back when our solar system formed? Or, even more excitedly, when that rock formed on Mars, what the atmosphere on Mars? We sampled the atmosphere of Mars using rocks sent to us from Mars before we ever got a space probe there.
Fraser Cain: There was one that landed in a lake in Alberta, I think, a couple of winters ago and the Chelyabinsk one, too, right? A big chunk of it went into a lake, which was really lucky because then, it’s a little more preserved. In the one in Alberta, it didn’t go all the way through the ice and so, they were actually able to go out when the – shortly after it had fallen and dig up the ice and actually get these perfectly preserved meteorites from the ground. With Chelyabinsk, we’ve got a piece of Chelyabinsk thanks to our good friend Richard Drum, the astronomy bum. Which is kind of amazing –
Dr. Pamela Gay: Yes, I actually have –
Fraser Cain: Have you got your Chelyabinsk meteorite right there?
Dr. Pamela Gay: Yes, I have it right here embedded on a spoamy that has a picture that was taken by one of the cameras, just happened to get lucky and record the impact explosion, bolide come fireball. So, yeah, bad things happen if you hear a – not if you hear, it’s too late when you hear it. If you see a fireball, there’s two chances you’ll hear it. One is, there’s gonna be a sonic boom, which is what happened at Chelyabinsk. You don’t want to be near glass when that sonic boom occurs and there’s another case of hearing it, which I think is what you were talking about earlier. Now, that time that you think you heard a fireball, what did you experience?
Fraser Cain: It sounded a little like, kind of crackling in the air. A little bit of like pop, crackle sound.
Dr. Pamela Gay: So there’s a lot of different reports of this kind of electronic noise and it’s always reported by people who are near metal. So there’s this idea that we can’t fully understand the physics, it’s just something that gets reported a lot. And different people publish papers and what they think it might be. But as far as I tell, we don’t have a conclusive understanding of the entire process that needs hearing it. But it’s called an electra-phonics sound and it has something to do with the ionization, the charge build up creating a crackling that we can hear sort of like you can sometimes hear St Elmo’s Fire.
Fraser Cain: That’s really cool, so if you want to increase your chances of getting a chance to see a fireball, I mean, not just a regular old meteor, but you want to see a fireball what should you do?
Dr. Pamela Gay: Look up.
Fraser Cain: Okay, well that’s the show everybody.
Dr. Pamela Gay: It’s – so, if you think about it, you’re only going to see these if you’re outside, looking at the sky. I’ve seen, other than that one time I saw the Leonid’s, I’ve seen a bunch of fireballs while I was out driving in wide, open spaces. I live in the American Midwest, we do flat really well, which means we can see far out, great distances, lots of sky. And so, driving, it gives me a large swath I can view, but I’m still not seeing a whole sky.
I’m missing anything that is above me or behind me. The best thing you can do is find yourself a great hammock and have it nice and taunt so that you’re looking straight up. Go outside, stick a favorite podcast or audiobook in your ears and just look at the stars for things that, well, move faster than planets.
Fraser Cain: Yeah, I mean, this is one of those things that you get out of it what you put into it. That the more time you spend out in the nature, looking up and appreciating the wonder of the Cosmos, the higher the chances you are – of seeing a really bright fireball and that, one in – I don’t know what the percentage is, let’s say one tenth of one percent of all the fireballs. If you see, whatever, a thousand meteors, you’re gonna see one fireball. Like, it’s just a numbers game, so get out there and see. Don’t live on the west coast or British Columbia, I think is good advice, as well because –
Dr. Pamela Gay: You need clear skies.
Fraser Cain: All we have is rain, every time I’m like, I’m gonna get a telescope, no I don’t really need much of a telescope. I’ve got a good pair of binoculars and a small telescope, but you know.
Dr. Pamela Gay: So it’s really one of those cases of these things happen a thousand times a night, but if you don’t look up, you’re never gonna see one. And even if you go out during meteor shower, it doesn’t necessarily change your probabilities all that much for a lot of meteor showers. Because a lot of meteor showers are the less than magnitude four, not quite as bright. Little, just normal meteors shooting across the sky, these really super bright bolides and super bright fireballs, those are there every night. You just need to go out and look.
Fraser Cain: There you go, you can’t see it if you don’t get out in it, so. That is really the lesson we’ve learned all the time. Is that you just – if you just stay inside, play your video games, you won’t get a chance to see – watch your TV, you won’t get a chance to see the wonder of the Cosmos. It’s unfolding around you, all the time.
Dr. Pamela Gay: Now, one final thing before we go away, is you don’t somebody have to have eyeballs to perceive the fireballs, they just help. If you take a radio outside, not Sirius Radio, but an actual, honest to goodness FM radio, if you take a radio outside, tune it to the space between stations. That crackly, staticy, you’ll sometimes hear significantly louder squeals and pops and those would be audio versions of the fireballs as they streak through the sky and reflect back radio stations to greatly Doppler shifted and other different things that generate this radio noise that allows us to get it. Perceiving these fireballs in a completely different light.
Fraser Cain: Yeah, and we love to hear your reports, so on the comments on our videos and stuff, by all means jump in and if you’ve had a chance to see a fireball in your life, we’d love to read about it, so. Well, thank you so much Pamela and we’ll talk to you next week, we’re down to just a couple of shows before the hiatus.
Dr. Pamela Gay: It’s great and we’re gonna miss you Preston, so for those of you don’t know, I’m just gonna put this into the action show. Preston Gibson, our audio producer, who’s been working with us for years and years and years, doing an amazing job, is going to retire from working on our show, so he can work on his professional career and will get a few hours back in his life to have a life. We’re really proud of him for everything he’s accomplished and he will be sorely missed and we’re really greatly proud to see what he’s accomplished. So, I’m gonna shut up now.
Fraser Cain: Thanks Preston, what she said. All right, thanks Pamela, we’ll see you next week.
Dr. Pamela Gay: Good bye.
Male Announcer: Thanks for listening to Astronomy Cast, a non-profit resource provided by Astrosphere New Media Association, Fraser Cain and Dr. Pamela Gay. You can find show notes and transcripts for every episode at astronomycast.com. You can email us at email@example.com. Tweet us at Astronomy Cast, like us on Facebook or circle us Google Plus. We record our show live on Google Plus every Monday at 12 p.m. Pacific, 3 p.m. Eastern or 2000 Greenwich Mean Time. If you missed the live event, you can always catch up over at cosmosquest.org. If you enjoy Astronomy Cast, why not give us a donation? It helps us pay for bandwidth, transcripts and show notes. Just click the donate link on the website. All donations are tax deductible for US residence. You can support the show for free, too. Write a review or recommend us to your friends, every little bit helps. Click support the show on our website and see some suggestions. To subscribe to the show, point your pod catching software at astronomycast.com/podcast.xml or subscribe directly from iTunes. Our music is provided by Travis Earl and the show is edited by Preston Gibson.