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Why haven't we seen a Milky Way Supernova in 400 years? · Daniel and Kelly’s Extraordinary Universe

• 0:09
  Speaker 1: Katie, if you want to learn more about some creature
• 0:12
  Speaker 1: you're planning to feature, what's a good way to get started? Well,
• 0:16
  Speaker 1: I use this obscure technology called Google, or I could
• 0:21
  Speaker 1: find one and observe it. That's it. You just read
• 0:24
  Speaker 1: about it or observe it. You don't like poke it
• 0:27
  Speaker 1: or anything. I mean, in general, I think in the
• 0:30
  Speaker 1: field of evolutionary biology, they discourage poking wild animals. Yes.
• 0:35
  Speaker 1: Does that mean therefore that you also, like, never smashed
• 0:38
  Speaker 1: two of them together at high speeds? Pretty strongly discouraged. Interesting?
• 0:42
  Speaker 1: I mean, in my experience, that's a pretty good way
• 0:45
  Speaker 1: to learn what something's made out of. I think that
• 0:47
  Speaker 1: someone needs to find some advocacy organization or pro bono
• 0:52
  Speaker 1: lawyers to represent the protons you guys have been smashing. Oh,
• 0:55
  Speaker 1: we are facing the biggest class action lawsuit in history. Hi,
• 1:15
  Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
• 1:19
  Speaker 1: UC Irvine, and I am not prepared for a lawsuit
• 1:22
  Speaker 1: from ten to the thirty protons. Hi. I am Katie Golden.
• 1:26
  Speaker 1: I host the podcast Creature Feature, and I am boning
• 1:31
  Speaker 1: up on my lawyerism to try to sue the pants
• 1:36
  Speaker 1: and particles off of Daniel, how are you going to
• 1:39
  Speaker 1: manage all of those clients? I mean, what if they
• 1:41
  Speaker 1: disagree about how much money to ask for or you know,
• 1:44
  Speaker 1: whether to send me to prison or something. I mean,
• 1:46
  Speaker 1: tended the thirty clients is a lot to wrangle. I mean,
• 1:48
  Speaker 1: I think I'll just send out a general mailer or
• 1:51
  Speaker 1: do an ad on TV. That's like, if you're a particle,
• 1:54
  Speaker 1: and you are a loved particle were involved in a
• 1:57
  Speaker 1: smashing well, I hope that all the protons out there
• 2:00
  Speaker 1: are not mad at us for all the times we've
• 2:02
  Speaker 1: been smashing them together to try to learn about the
• 2:05
  Speaker 1: nature of the universe. And Welcome to the podcast Daniel
• 2:08
  Speaker 1: and Jorge Explain the Universe, a production of I Heart
• 2:12
  Speaker 1: Radio in which we do encourage people to smash stuff
• 2:16
  Speaker 1: together in order to learn about how the universe is
• 2:20
  Speaker 1: put together. We try to ask and answer some of
• 2:22
  Speaker 1: the deepest questions about the very nature of the universe,
• 2:26
  Speaker 1: the fundamental fabric of reality. What in the end is
• 2:30
  Speaker 1: the universe made out of our space and time, fundamental
• 2:34
  Speaker 1: our particles, the basic building blocks of the universe, Or
• 2:37
  Speaker 1: is it something even weirder, even deeper, even stranger than
• 2:41
  Speaker 1: our little minds can suppose, and we don't just smash
• 2:44
  Speaker 1: particles together. We look out into space to see other
• 2:47
  Speaker 1: things that Mother Nature or Grandpa Universe has smashed together
• 2:52
  Speaker 1: on our behalf, so that we can ask huge questions
• 2:55
  Speaker 1: about how those things are put together. The moral of
• 2:58
  Speaker 1: the story is smash stuff, learn a lot, but of course,
• 3:02
  Speaker 1: watch out for people's rights and be careful about applying
• 3:06
  Speaker 1: this to wild animals. My co host and friend Jorge
• 3:09
  Speaker 1: can't be here today. He is traveling through Spain and Portugal,
• 3:13
  Speaker 1: so we are delighted to have our regular co host,
• 3:15
  Speaker 1: Katie Golden. Katie, thanks very much for joining us. Yeah,
• 3:18
  Speaker 1: of course, I think it is a little bit suspicious
• 3:21
  Speaker 1: that Jorge is missing when we are talking about smashing
• 3:24
  Speaker 1: things together to learn more about them. But okay, and
• 3:28
  Speaker 1: you know, astronomers are always delighted when stuff smashes into
• 3:31
  Speaker 1: other stuff in outer space. They're not capable of building
• 3:35
  Speaker 1: a collider like we can. You know, we can smash
• 3:37
  Speaker 1: protons together to learn about what's inside of them, but
• 3:40
  Speaker 1: astronomers can't build a black hole collider for example. Yes,
• 3:46
  Speaker 1: they got dreams, they got plans, but sometimes they get
• 3:50
  Speaker 1: lucky anyway, and the stuff just sort of happens out
• 3:52
  Speaker 1: there in the universe for them to watch, and they
• 3:56
  Speaker 1: don't have to worry about the black holes rights or
• 3:58
  Speaker 1: it's legal fees or or whether he gets mad because
• 4:01
  Speaker 1: they're just taking notes. And I wonder, Katie, if the
• 4:03
  Speaker 1: same thing happens for you. I mean, sometimes I watch
• 4:06
  Speaker 1: these nature shows about like giraffe battling by slamming their
• 4:10
  Speaker 1: next together, or you know, big horn rams being in
• 4:12
  Speaker 1: themselves together. You guys also learn a lot, don't you
• 4:15
  Speaker 1: when animals smash themselves together. Yeah, I mean, to be fair,
• 4:19
  Speaker 1: I am not currently doing research, but when I was
• 4:22
  Speaker 1: a little undergrad, I was definitely involved in some of
• 4:26
  Speaker 1: these research projects. And one of them was just going
• 4:29
  Speaker 1: out and watching squirrels and taking notes, and it made
• 4:33
  Speaker 1: us very popular among the school body, just sitting there
• 4:36
  Speaker 1: being the squirrel people, watching the squirrels, writing down what
• 4:40
  Speaker 1: the squirrels were doing. But yes, observing wildlife, observing animals
• 4:44
  Speaker 1: is extremely instructive for revolutionary biologists. It can be very
• 4:49
  Speaker 1: difficult because, of course, when you're observing things in nature,
• 4:52
  Speaker 1: it is not a laboratory environment, so you know, eliminating
• 4:56
  Speaker 1: the variables that are inevitable when you have sort of
• 5:00
  Speaker 1: this chaotic natural environment can pose a kind of tricky
• 5:04
  Speaker 1: thing for research, But yeah, it is. It is a
• 5:06
  Speaker 1: hugely important side of evolutionary biology is just looking at
• 5:11
  Speaker 1: what an animal is doing and hoping it doesn't notice
• 5:15
  Speaker 1: you looking at it. All right, But I want to
• 5:17
  Speaker 1: clear answer here. Do squirrels smash themselves together or not?
• 5:22
  Speaker 1: They smash acorns into their little faces, but they don't
• 5:27
  Speaker 1: smash acorns against each other's no, like squirrel acorn Collision
• 5:31
  Speaker 1: research program, not exactly. They may smash it into the
• 5:35
  Speaker 1: ground a little bit to get that buried in there,
• 5:38
  Speaker 1: but they don't have a squirrel acorn hadron collider quite yet. Well,
• 5:44
  Speaker 1: you know, there's just a limitation to how much you
• 5:46
  Speaker 1: can learn by observing stuff. We were just looking at protons,
• 5:50
  Speaker 1: for example, we never would have understood what was inside
• 5:53
  Speaker 1: them and seeing this incredible dance of the corks and
• 5:56
  Speaker 1: the gluons that are all tied together to make this
• 5:59
  Speaker 1: crazy thing we call a proton. And so it's these
• 6:01
  Speaker 1: dramatic events when protons smashed together or when larger objects
• 6:05
  Speaker 1: smashed together. Squirrels black holes for example, a list nobody
• 6:10
  Speaker 1: has ever made before in the history of time that
• 6:11
  Speaker 1: consists only of squirrels and black holes seems pretty complete
• 6:16
  Speaker 1: to me. What else could there be onside a list?
• 6:19
  Speaker 1: But when these things do happen, you have an incredible
• 6:21
  Speaker 1: opportunity to learn something about the nature of what's inside
• 6:25
  Speaker 1: these objects. I mean, we know something about what's inside squirrels,
• 6:29
  Speaker 1: but we have deep questions about what's at the heart
• 6:31
  Speaker 1: of neutron stars, what's inside black holes? Hey, what's going
• 6:35
  Speaker 1: on even inside normal stars? Stars like our sun have
• 6:39
  Speaker 1: incredible convection zones of plasma slurping and slashing and making
• 6:44
  Speaker 1: magnetic fields that flip every eleven years, we still don't
• 6:48
  Speaker 1: even understand what's going on inside a normal star. To
• 6:51
  Speaker 1: be fair, if you want to know what's going inside
• 6:55
  Speaker 1: of a squirrel, you can't really do that just by
• 6:58
  Speaker 1: watching the squirrel. Uh. It involves the process that I
• 7:03
  Speaker 1: may not want to describe to people right now, but
• 7:06
  Speaker 1: I imagine it is quite difficult to know in a
• 7:09
  Speaker 1: similar way what is going on inside something like a
• 7:12
  Speaker 1: star when you can only look at it and not
• 7:15
  Speaker 1: dissect it on a table. Yeah, and even star collisions
• 7:20
  Speaker 1: are pretty rare, But astronomers are lucky that there's another
• 7:23
  Speaker 1: way to see inside of stars. You don't have to
• 7:26
  Speaker 1: smash them together. Sometimes they just blow up on their own.
• 7:30
  Speaker 1: They erupt and deposit all of their innerds now on
• 7:33
  Speaker 1: their outers, so that we can study them and see
• 7:36
  Speaker 1: what was inside that star, just like squirrels, just like
• 7:41
  Speaker 1: got to one too many acorns, right exactly, I'm stuffed.
• 7:46
  Speaker 1: And when stars do go boom, it's an incredible opportunity
• 7:50
  Speaker 1: to learn about the processes that are going on inside
• 7:53
  Speaker 1: the star, why they suddenly got imbalanced. Plus it's a
• 7:56
  Speaker 1: pretty dramatic light show. Now you say that, but I
• 8:00
  Speaker 1: have never gotten to see a star explode, and I
• 8:03
  Speaker 1: would really like to. So where can I sign up? Well,
• 8:06
  Speaker 1: one problem is that we don't even really understand why
• 8:09
  Speaker 1: it happens and when it happens. We don't have a
• 8:12
  Speaker 1: scientific model that can predict when a given star is
• 8:15
  Speaker 1: going to go supernova. So all we can do is
• 8:18
  Speaker 1: scan the night sky. And you know, to me, that's
• 8:21
  Speaker 1: fascinating because the night sky seems pretty stable. If you
• 8:24
  Speaker 1: like looking at the stars, you probably are looking at
• 8:27
  Speaker 1: the same stars that looked pretty much the same as
• 8:29
  Speaker 1: your parents did, and your grandparents and their ancestors did.
• 8:34
  Speaker 1: The night sky does not change very much, but when
• 8:37
  Speaker 1: it does, when that happens, when a supernova goes boom,
• 8:40
  Speaker 1: it's very dramatic. These things can be as bright as
• 8:43
  Speaker 1: an entire galaxy, so it's a pretty exciting event when
• 8:47
  Speaker 1: it does happen. But you know, you're right, it's not
• 8:50
  Speaker 1: something that we've been able to see very recently, and
• 8:53
  Speaker 1: even though supernovas are expected to be rare, something of
• 8:57
  Speaker 1: a mystery about why we haven't seen more supernovas. In fact,
• 9:01
  Speaker 1: it's been over four hundred years since we have seen
• 9:05
  Speaker 1: a supernova in our galaxy. It seems strange to me
• 9:09
  Speaker 1: because even if it's rare, it seems like there's so
• 9:12
  Speaker 1: much stuff in the galaxy that you would at you know,
• 9:17
  Speaker 1: you are increasing your odds. Like when they say an
• 9:20
  Speaker 1: infinite number of monkeys on an infinite number of typewriters.
• 9:23
  Speaker 1: It's like an infinite maybe not infinite, but many many
• 9:26
  Speaker 1: exploding monkeys who once in a while explode. You would
• 9:30
  Speaker 1: think you'd catch a monkey explode. I'm so sorry to
• 9:36
  Speaker 1: everybody out there who just had the mental image of
• 9:38
  Speaker 1: an exploding monkey put into their head. I hope that's
• 9:41
  Speaker 1: a positive addition to your day. Whatever else is going on,
• 9:44
  Speaker 1: which we don't condone. We do not condone it. We
• 9:47
  Speaker 1: simply describe it exactly scientifically. We're just observing super monkey nova's.
• 9:52
  Speaker 1: You know, it's not our fault. We're just you know,
• 9:54
  Speaker 1: doing our best to learn something from it. So that's
• 9:56
  Speaker 1: exactly what we're gonna be talking about today. The title
• 9:59
  Speaker 1: of today's AT episode is why haven't we seen a
• 10:07
  Speaker 1: Milky Way supernova in more than four hundred years? Have
• 10:11
  Speaker 1: we just not looked up? Like, has anyone you know,
• 10:15
  Speaker 1: just kind of checked it out? You mean, have we
• 10:17
  Speaker 1: been so self involved for the last four hundred years
• 10:19
  Speaker 1: that we haven't noticed incredible explosions in our sky? Right?
• 10:23
  Speaker 1: It's these kids with their noses and their smartphones all
• 10:26
  Speaker 1: the time. They just don't notice them. Well, I think
• 10:29
  Speaker 1: that the last person to see a supernova in the
• 10:32
  Speaker 1: Milky Way was Kepler, himself, famous man of astronomy, of course,
• 10:37
  Speaker 1: and I'm pretty sure that he didn't have a smartphone,
• 10:39
  Speaker 1: and that in most of the intervening four hundred years,
• 10:43
  Speaker 1: astronomers have not been distracted by their smartphones. So that's
• 10:47
  Speaker 1: a good idea. But I think we're gonna have to
• 10:48
  Speaker 1: look for other explanations for why we haven't seen any
• 10:51
  Speaker 1: supernovas from the Milky Way in our sky in four
• 10:55
  Speaker 1: hundred years. It's something of a cosmic mystery that we're
• 10:58
  Speaker 1: going to dig into today, but before we do, we
• 11:01
  Speaker 1: were wondering what our listeners thought about this question. People
• 11:04
  Speaker 1: understand why there hasn't been a supernova in our galaxy
• 11:08
  Speaker 1: that we've spotted in several hundred years. So thanks very
• 11:12
  Speaker 1: much to everybody who volunteered to answer random questions. They
• 11:15
  Speaker 1: heard this question without any chance to prepare, and we
• 11:18
  Speaker 1: asked them to just speak from the top of their head,
• 11:21
  Speaker 1: so we get a sense for what you, dear listener,
• 11:24
  Speaker 1: are thinking about as you listen to this podcast episode.
• 11:27
  Speaker 1: What you know, what you don't know? What the ideas
• 11:29
  Speaker 1: are out there. If you'd like to hear your voice
• 11:31
  Speaker 1: speculating on the podcast for a future episode, please write
• 11:34
  Speaker 1: to us. We'd love to have you on the show.
• 11:36
  Speaker 1: Just drop us an email to questions at Daniel and
• 11:39
  Speaker 1: Jorge dot com. Here's what our listeners had to say.
• 11:43
  Speaker 1: If I remember rightly, there are a couple hundred billion
• 11:47
  Speaker 1: stars in the Milky Way, and supernovas are made from
• 11:50
  Speaker 1: stars that last much shorter than ours. So if they
• 11:55
  Speaker 1: were all eligible, there the right kind to be a
• 11:59
  Speaker 1: super nova and being produced at a constant right throughout
• 12:04
  Speaker 1: the life of the universe, we'd be seeing about one
• 12:08
  Speaker 1: every two and a half years, if I've done my
• 12:11
  Speaker 1: math right. Since we haven't seen one in at least
• 12:14
  Speaker 1: four hundred years, which is about a hundred and sixty
• 12:18
  Speaker 1: times as long as expected, my guess is that only
• 12:23
  Speaker 1: about one in a hundred and sixty stars is the
• 12:27
  Speaker 1: right kind to end up as a supernova. I've actually
• 12:30
  Speaker 1: thought about this question a couple of times, because, like
• 12:33
  Speaker 1: most people, I would love to see a supernova in
• 12:36
  Speaker 1: broad daily. I keep asking beetle juice, but it doesn't listen.
• 12:40
  Speaker 1: So I think that in individual galaxies they are just
• 12:45
  Speaker 1: a rare event. Um, there's only so many stars in
• 12:48
  Speaker 1: a galaxy, so I think they're pretty rare on a
• 12:51
  Speaker 1: galaxy scale, but on a universal scale, because there's countless galaxies,
• 12:56
  Speaker 1: they become common events. So that's my guess. Years is
• 13:00
  Speaker 1: like a blink of an eye in the galactic time scales.
• 13:04
  Speaker 1: So I think we just haven't seen a supernova in
• 13:08
  Speaker 1: our Milky Way yet. We haven't seen a Milky Way
• 13:12
  Speaker 1: supernova in more than four hundred years, because supernova are
• 13:16
  Speaker 1: not just that frequent. Quite a bit of the Milky
• 13:21
  Speaker 1: Way galaxy is hi didn't behind various gas clouds and
• 13:27
  Speaker 1: the central budge, so we don't see what's happening on
• 13:31
  Speaker 1: the other side of the lisk. But what is the
• 13:33
  Speaker 1: rate of supernova occurrence? I have no idea. I think
• 13:37
  Speaker 1: the answer to this is that there's probably a statistical
• 13:40
  Speaker 1: anomally that if the Sun has been around for five
• 13:44
  Speaker 1: billion years and there's like a billion stars in our
• 13:48
  Speaker 1: galaxy or a couple of billion stars in the galaxy,
• 13:52
  Speaker 1: and that not every star turns into a supernova, you
• 13:55
  Speaker 1: might just seduce the statistics suggests that one might not
• 13:59
  Speaker 1: have during this time, that one might happen in a
• 14:03
  Speaker 1: reasonable period of time. But four under views is not
• 14:05
  Speaker 1: a reasonable period of time in terms of the galaxy.
• 14:09
  Speaker 1: This question reminds me of the question that I asked
• 14:13
  Speaker 1: my grandmother when she was trying to tell me about
• 14:17
  Speaker 1: God and angels and all that good stuff. And I
• 14:23
  Speaker 1: would ask her, but Grandma, why can't we see angels?
• 14:28
  Speaker 1: Why can't we see these things that you're talking about
• 14:31
  Speaker 1: that used to be a long time ago? And she
• 14:36
  Speaker 1: was telling me that the reason is that people are bad,
• 14:41
  Speaker 1: not the people used to be good before then, and
• 14:44
  Speaker 1: that's why we could see all that stuff. Now we
• 14:47
  Speaker 1: are bad and they won't. We cannot see them anymore.
• 14:51
  Speaker 1: They won't appear before our eyes. So with the milk,
• 14:55
  Speaker 1: keep with supernova. Could say, also, it's a combination of
• 14:59
  Speaker 1: dus distance and dumb luck that we cannot see them,
• 15:03
  Speaker 1: but also might be because we are bad. I love
• 15:08
  Speaker 1: the idea that we've just been too naughty to see
• 15:12
  Speaker 1: a supernova. This is our punishment. It's like some kind
• 15:16
  Speaker 1: of galactic council has like, oh, humans destroying your environment, naughty, naughty,
• 15:22
  Speaker 1: no supernovas for you. I know, like we don't deserve
• 15:25
  Speaker 1: a supernova. You know, we haven't earned it. It's for
• 15:28
  Speaker 1: like the good aliens, not for us. Right, we got
• 15:31
  Speaker 1: to clean our rooms and rainforests before we get a supernova. Yeah, exactly.
• 15:38
  Speaker 1: I like the idea that the universe is judging us.
• 15:40
  Speaker 1: But I think that the rest of the listener has
• 15:42
  Speaker 1: really put their finger on sort of the spectrum of
• 15:44
  Speaker 1: ideas here. You know, it's true that we haven't seen
• 15:46
  Speaker 1: one in four hundred years, but is that unexpected? Do
• 15:49
  Speaker 1: we think we should have seen one in four hundred years,
• 15:52
  Speaker 1: because it's true that four years feels like a long
• 15:56
  Speaker 1: time to us humans, but it's just a blink on
• 15:59
  Speaker 1: cosmic iron scales or processes play out over millions and
• 16:03
  Speaker 1: billions of years. So it's a fair question whether or
• 16:06
  Speaker 1: not we should have expected to see one, right, because
• 16:08
  Speaker 1: like if you're you know, if you live in England,
• 16:12
  Speaker 1: you expect to see rain all the time, but if
• 16:15
  Speaker 1: you live in Southern California you never see rain ever,
• 16:19
  Speaker 1: So the different environments between Southern California and England, you
• 16:25
  Speaker 1: will have kind of a different expectation for these phenomenon. So,
• 16:29
  Speaker 1: you know, when we don't see stuff in the Milky Way,
• 16:32
  Speaker 1: I guess I'm asking is the Milky Way like, should
• 16:35
  Speaker 1: it be exploding all the time? Is it more of
• 16:37
  Speaker 1: a southern California? What is the weather of the Milky Way? Well,
• 16:42
  Speaker 1: you know, meteorologists are famously bad at predicting supernovas. You know,
• 16:46
  Speaker 1: they say they're going to come on Tuesday afternoon and
• 16:48
  Speaker 1: then boom Wednesday afternoon. When you make your picnic, that's
• 16:51
  Speaker 1: when all the supernovas come. And I'm always dressed the
• 16:54
  Speaker 1: wrong way. What is your supernova outfit look like Katie.
• 16:59
  Speaker 1: It's very shiny, lots of lots of frills and shoulder pads.
• 17:05
  Speaker 1: Of course, well, I think you put your finger on
• 17:07
  Speaker 1: the question, and so we are going to talk about
• 17:09
  Speaker 1: that today. How often we expect to see supernovas in
• 17:13
  Speaker 1: our galaxy and then ideas for why we are not
• 17:15
  Speaker 1: seeing as many as we expect. But first maybe we
• 17:18
  Speaker 1: should talk about the basics, for example, like what is
• 17:21
  Speaker 1: a supernova, how does it work, what do we know
• 17:23
  Speaker 1: about it? And why is it even possible to see
• 17:26
  Speaker 1: one from so far away? I mean from the name,
• 17:29
  Speaker 1: it sounds like it's a nova, but really big and
• 17:33
  Speaker 1: super they are in fact the nova and nova is
• 17:35
  Speaker 1: a Latin word that means new, and so the name
• 17:38
  Speaker 1: supernova actually comes from another famous man of astronomy, Tico
• 17:43
  Speaker 1: bra Hey, who observed one in the fifteen hundreds, and
• 17:46
  Speaker 1: he wrote a book about them, whose title is in
• 17:48
  Speaker 1: Latin but includes the words nova and stella as in
• 17:52
  Speaker 1: new star. And the word nova was later used to
• 17:55
  Speaker 1: describe new things in the sky, including supernova super new
• 17:59
  Speaker 1: things in the sky. That's really interesting because I think
• 18:02
  Speaker 1: of a star exploding is kind of like the death
• 18:06
  Speaker 1: of a star, the violent death of a star. But yeah,
• 18:09
  Speaker 1: nova being like it's something new, some kind of new thing,
• 18:14
  Speaker 1: is I guess a nicer way to think about it. Yeah. Well,
• 18:18
  Speaker 1: often these things that are blowing up are in other galaxies,
• 18:22
  Speaker 1: really far away things that we couldn't see. The star
• 18:24
  Speaker 1: that exploded was individually way too dim for us to
• 18:28
  Speaker 1: see with the naked eye. But once it becomes a supernova,
• 18:31
  Speaker 1: it can outshine the entire galaxy that is in becoming
• 18:35
  Speaker 1: visible and bright in the sky. So you're right that
• 18:38
  Speaker 1: when a star goes supernova, it's at the end of
• 18:40
  Speaker 1: its life, so it's not really new. It's new to
• 18:43
  Speaker 1: us because it went from totally invisible in the sky,
• 18:47
  Speaker 1: one star out of billions in a distant galaxy, to
• 18:50
  Speaker 1: something that is now visible, so it's new in the sky.
• 18:54
  Speaker 1: That's interesting to me that it's so bright, because when
• 18:56
  Speaker 1: I think of something dying, I think of it's sort
• 19:00
  Speaker 1: of fading, you know, like when a light bulb dies,
• 19:03
  Speaker 1: it kind of fades, it flickers out, or when a
• 19:05
  Speaker 1: candle dies, it flickers out. But if it's really bright,
• 19:09
  Speaker 1: if after it dies it explodes and creates something really bright,
• 19:13
  Speaker 1: it sounds like it's releasing a huge amount of energy.
• 19:16
  Speaker 1: It seems counterintuitive to it being a dying star. That's
• 19:21
  Speaker 1: a good point, and it shines a light right on
• 19:23
  Speaker 1: what's going on in the supernova, because supernovas are not
• 19:26
  Speaker 1: like fires that burn gently for a long time and
• 19:29
  Speaker 1: then eventually just sort of flicker out and fade. They're
• 19:33
  Speaker 1: more like a bomb, right where the fuse is going
• 19:36
  Speaker 1: for a long time and then most of the energy
• 19:38
  Speaker 1: is released at the very very end. Right, it's very
• 19:41
  Speaker 1: dramatic sort of ending of the life of an object.
• 19:44
  Speaker 1: And you know, interestingly, the same thing is sort of
• 19:46
  Speaker 1: true of black holes. Black holes evaporate, you leave them
• 19:50
  Speaker 1: out in the middle of space, and they do so
• 19:52
  Speaker 1: by giving off hawking radiation. And the hawking radiation they
• 19:56
  Speaker 1: give off is brighter as the black hole gets small.
• 20:00
  Speaker 1: So as the black hole gives off radiation gets smaller
• 20:03
  Speaker 1: and smaller, it starts to give off more and more radiation.
• 20:06
  Speaker 1: So the last gasp of a black hole would actually
• 20:09
  Speaker 1: be very bright. You would like go off in a
• 20:11
  Speaker 1: bang of glory. That's I love that, that's I'm proud
• 20:15
  Speaker 1: of them, that's good for them. Is that how you
• 20:17
  Speaker 1: want to go out, Katie, You don't want to just
• 20:19
  Speaker 1: podcast to the end, dribbling out a few last words.
• 20:22
  Speaker 1: You want to have like one dramatic podcast at the
• 20:25
  Speaker 1: very end of your career. Exactly. Yeah, if I could
• 20:29
  Speaker 1: go the way a black hole goes, and you know,
• 20:32
  Speaker 1: just like shootout podcast rays everywhere all at once, that'd
• 20:37
  Speaker 1: be great, right, the super podcast nova. Well, in order
• 20:41
  Speaker 1: to understand why supernovas are so bright and so dramatic,
• 20:45
  Speaker 1: we have to think a little bit about what's going
• 20:48
  Speaker 1: on inside them. Now, like everything out there in the universe,
• 20:51
  Speaker 1: it's not something that we understand very well, but we
• 20:54
  Speaker 1: do have something of a reasonable cartoon description of what's
• 20:58
  Speaker 1: going on why supernovas are o dramatic. And remember, the
• 21:01
  Speaker 1: context is how a star works at all, Like why
• 21:05
  Speaker 1: are there stars anyway? You know? Which you have is
• 21:08
  Speaker 1: a huge blob of gas and dust in the universe
• 21:10
  Speaker 1: which gravity has gathered together into a compact, dense object,
• 21:15
  Speaker 1: and squeezing it together makes it hot. And then because
• 21:19
  Speaker 1: it's so hot and so dense, it triggers fusion in
• 21:22
  Speaker 1: the heart of the star. So you squeeze hydrogen together,
• 21:25
  Speaker 1: for example, and you get helium. You get those two
• 21:28
  Speaker 1: protons to overcome their positive charges and to pop together
• 21:32
  Speaker 1: into a new kind of thing. That helium gets fused
• 21:35
  Speaker 1: together into something even heavier. And the cool thing about
• 21:38
  Speaker 1: fusion is that it doesn't just make heavier stuff. It
• 21:41
  Speaker 1: also releases a lot of energy. So gravity pulls this
• 21:44
  Speaker 1: stuff together and then creates the conditions necessary for fusion,
• 21:48
  Speaker 1: which pushes back out. So the energy from fusion, the particles,
• 21:52
  Speaker 1: the photons, pushes back out on the star. And that's
• 21:55
  Speaker 1: why the star can burn for billions of years. That's
• 21:58
  Speaker 1: why you get like a stable, say, situation, like why
• 22:01
  Speaker 1: do stars even happen? Because there's this incredible balance between
• 22:05
  Speaker 1: gravity pushing in on the star, trying to make it
• 22:08
  Speaker 1: into a black hole, and fusion pushing out on the star,
• 22:12
  Speaker 1: basically a bomb blowing the star up. And these two
• 22:15
  Speaker 1: things can stay in balance for billions of years, depending
• 22:18
  Speaker 1: on how massive the star is. But one thing I
• 22:21
  Speaker 1: know about stars, since we have one, and it's called Mr.
• 22:25
  Speaker 1: Sun or Mrs Son, it gives off heat. So this
• 22:28
  Speaker 1: to me seems to indicate that, like, you know, this
• 22:31
  Speaker 1: is not like a self contained system. If I can
• 22:34
  Speaker 1: feel the Sun, feel the warmth from it, and it
• 22:37
  Speaker 1: doesn't that mean it is losing energy at some kind
• 22:40
  Speaker 1: of rate, Like, is it in the same way as
• 22:43
  Speaker 1: like a fire burns fuel, is it running out of
• 22:46
  Speaker 1: fuel as it burns? The star definitely is giving off energy.
• 22:50
  Speaker 1: It's not self contained, so it is using up fuel,
• 22:54
  Speaker 1: and the fuel four fusion are light elements, so mostly hydrogen.
• 22:58
  Speaker 1: Hydrogen is the most plentiful thing in the universe. Most
• 23:01
  Speaker 1: of the universe that's made out of baryonic matter like
• 23:03
  Speaker 1: protons and neutrons and our kind of stuff is hydrogen.
• 23:06
  Speaker 1: So there's no shortage of hydrogen around. And most of
• 23:09
  Speaker 1: the life of a star is burning that hydrogen and
• 23:12
  Speaker 1: turning it into something heavier helium, and then if it's
• 23:14
  Speaker 1: big enough and heavy enough, it can create the conditions
• 23:17
  Speaker 1: to burn that helium into something heavier, and if it's
• 23:20
  Speaker 1: then hot enough to burn the results of that fusion,
• 23:23
  Speaker 1: it can just keep going heavier and heavier and heavier
• 23:26
  Speaker 1: until it gets up about too iron. In each case, though,
• 23:29
  Speaker 1: You're right, it's using up some of the energy stored
• 23:32
  Speaker 1: in those light elements to turn into heavier elements and
• 23:35
  Speaker 1: give up some of that energy, right, So, like where
• 23:38
  Speaker 1: does that energy come from? It comes from the original
• 23:40
  Speaker 1: energy of that hydrogen. You know, you have that hydrogen,
• 23:43
  Speaker 1: it's floating around in the universe. You now squeezed it
• 23:46
  Speaker 1: down to a very compact object a star. It's buzzing around,
• 23:50
  Speaker 1: it's very high temperature. Now you've captured those protons into
• 23:53
  Speaker 1: helium and in doing so, they give up some of
• 23:55
  Speaker 1: that energy, which then gets radiated away into space to
• 23:59
  Speaker 1: make you have a nice summer southern California day. I
• 24:02
  Speaker 1: don't know about nice, but yes, uh, given how hot
• 24:06
  Speaker 1: it has been, thanks Son. So I guess like I'm curious,
• 24:10
  Speaker 1: like when a star dies, is it running out of
• 24:14
  Speaker 1: fuel or is it like collapse and getting too heavy,
• 24:18
  Speaker 1: because it seems like that one of those things would
• 24:22
  Speaker 1: quote unquote kill the star right exactly. It's definitely not
• 24:25
  Speaker 1: running out of fuel. When a star dies and go supernova,
• 24:28
  Speaker 1: there's still an enormous amount of hydrogen left over, and
• 24:32
  Speaker 1: that's why the star doesn't die in a quiet fizzle.
• 24:34
  Speaker 1: It's not just like burning through all of its fuel.
• 24:37
  Speaker 1: But what's happening is that this balance between gravity and
• 24:40
  Speaker 1: fusion is getting upset. And there's really two different kinds
• 24:44
  Speaker 1: of supernova is that we should talk about. One of
• 24:46
  Speaker 1: them is called core collapse, and what happens there is
• 24:49
  Speaker 1: that the star is making this ash, this product of fusion,
• 24:54
  Speaker 1: making heavier and heavier elements which then settle at the
• 24:57
  Speaker 1: heart of the star. And if the star is not
• 24:59
  Speaker 1: heavy enough to create the high temperatures needed to burn
• 25:02
  Speaker 1: that into something even heavier than it's like inert material
• 25:06
  Speaker 1: at the heart of the star. So now at the
• 25:08
  Speaker 1: heart of the star you are no longer producing a
• 25:10
  Speaker 1: lot of energy, and so this balance between gravity and
• 25:13
  Speaker 1: fusion tips towards gravity, and gravity rushes in and collapses
• 25:18
  Speaker 1: the star. The star collapses, but it doesn't just like
• 25:20
  Speaker 1: suddenly go out. Collapse makes it super dense and so
• 25:24
  Speaker 1: super hot inside the star and quickly burns through a
• 25:28
  Speaker 1: huge amount of fuel. So first gravity is the upper
• 25:32
  Speaker 1: hand to cause this collapse, but then fusion surges back
• 25:35
  Speaker 1: and blows it outwards again, and it leaves behind a
• 25:38
  Speaker 1: very dense core which is gonna be a black hole
• 25:40
  Speaker 1: or a neutron star. So you mentioned earlier that it
• 25:43
  Speaker 1: is it's this push and shove kind of where gravity
• 25:48
  Speaker 1: is trying to push it inwards like almost to create
• 25:51
  Speaker 1: like a black hole, and then there's the push out.
• 25:53
  Speaker 1: And so once that outward pushing is like outweighed by
• 25:57
  Speaker 1: the inward pushing, the heaviness of the inward pushing. Why
• 26:01
  Speaker 1: doesn't it just become a black hole all the time? Right?
• 26:05
  Speaker 1: So gravity wants to make everything a black hole. Right.
• 26:07
  Speaker 1: Gravity can only do one thing, which is pulls stuff together,
• 26:10
  Speaker 1: and if there was only gravity in the universe, eventually
• 26:13
  Speaker 1: it would just make everything into a black hole. The
• 26:16
  Speaker 1: reason that things aren't a black holes that there's some
• 26:18
  Speaker 1: way to resist it. Like why isn't the Earth a
• 26:21
  Speaker 1: black hole? It's a big blob of mass. Why doesn't
• 26:24
  Speaker 1: gravity squeeze it down into a peanut and make it
• 26:27
  Speaker 1: a black hole? The answer is that the Earth is
• 26:29
  Speaker 1: structurally strong enough to resist gravity. Gravity actually kind of
• 26:33
  Speaker 1: a weakling, not really a very powerful force. It's like
• 26:37
  Speaker 1: ten to the thirty times weaker than all the other forces.
• 26:40
  Speaker 1: So you just need something to be able to resist it.
• 26:43
  Speaker 1: So fusion can resist it for a long time, but eventually,
• 26:46
  Speaker 1: as the star gets more and more massive at its core,
• 26:48
  Speaker 1: gravity is winning and fusion is losing. So what happens
• 26:51
  Speaker 1: when a supernova collapse? Sometimes you do get a black
• 26:54
  Speaker 1: hole at its heart. It depends on the mass of
• 26:56
  Speaker 1: the original star. Sometimes you get a black hole. Sometimes, however,
• 27:00
  Speaker 1: there's another stage, like a neutron star can be formed,
• 27:03
  Speaker 1: So the incredible dense core that's left over after the
• 27:06
  Speaker 1: supernova happens can be another kind of matter which resists
• 27:10
  Speaker 1: collapse into a black hole. But again, neutron stars are
• 27:13
  Speaker 1: not something that we understand very well. We did an
• 27:16
  Speaker 1: episode recently about what's inside a neutron star. It's something
• 27:19
  Speaker 1: that scientists are still exploring. So it's sort of like
• 27:22
  Speaker 1: a ladder of ways that you can avoid black hole
• 27:25
  Speaker 1: collapse if you can make the right kind of matter,
• 27:27
  Speaker 1: or you can sort of like hold up against the
• 27:29
  Speaker 1: trash compactor of gravity trying to squeeze you down into
• 27:32
  Speaker 1: a black hole, So it could become a black hole,
• 27:35
  Speaker 1: could become something like a neutron star. Do we know
• 27:38
  Speaker 1: like why it becomes a supernova sometimes, like what would
• 27:41
  Speaker 1: cause that explosion rather than it just collapsing. So supernova
• 27:46
  Speaker 1: is when it starts to collapse. It's like an implosion
• 27:48
  Speaker 1: and you get this shock wave that's traveling towards the
• 27:51
  Speaker 1: center of the star and then it hits the core
• 27:53
  Speaker 1: and it bounces back and you get the supersonic shock
• 27:56
  Speaker 1: wave that comes out and blows out all of this material,
• 28:00
  Speaker 1: huge amounts of light are released because you have a
• 28:02
  Speaker 1: lot of fusion happening all at once. You know, a
• 28:04
  Speaker 1: star is like a very slow burn, using a very
• 28:07
  Speaker 1: tiny fraction of its fuel every year, and the supernovit
• 28:11
  Speaker 1: it can use of a big fraction of its fuel
• 28:13
  Speaker 1: all at once, which is how it can become brighter
• 28:16
  Speaker 1: than the entire galaxy around it. It also spews a
• 28:20
  Speaker 1: lot of that material out into space. So you have
• 28:23
  Speaker 1: this implosion that creates very high temperatures, very briefly, a
• 28:26
  Speaker 1: lot of really really rapid fusion, and then it blows
• 28:29
  Speaker 1: up and sends a lot of that energy in terms
• 28:31
  Speaker 1: of photons and protons and just like raw star stuff
• 28:35
  Speaker 1: out into space. So just a hypothetical, it'd be like
• 28:40
  Speaker 1: a kid throwing a ball against a wall really hard,
• 28:44
  Speaker 1: and again hypothetically the ball like shooting back out because
• 28:48
  Speaker 1: you threw it against the wall really hard and hitting
• 28:50
  Speaker 1: you in the face. But that times like a billion
• 28:54
  Speaker 1: with a billion children and a billion balls. Yeah, and
• 28:58
  Speaker 1: it's not something that we can under stand because there's
• 29:01
  Speaker 1: a lot of really strong forces involved and it's all
• 29:03
  Speaker 1: of very fast physics. So you know, we can't look
• 29:06
  Speaker 1: at a star and say this one's gonna go supernova
• 29:09
  Speaker 1: in forty two point two billion years, or this one's
• 29:12
  Speaker 1: gonna go supernova tomorrow. It's the kind of thing we
• 29:15
  Speaker 1: just sort of like see happening, and we're like, oh, everybody,
• 29:17
  Speaker 1: watch that one. Watch that one, and we're trying to
• 29:20
  Speaker 1: understand what goes on inside it. But modeling the process
• 29:23
  Speaker 1: of a supernova is not something we're capable of yet.
• 29:26
  Speaker 1: You know, when we want to understand something in physics,
• 29:28
  Speaker 1: either we find like a set of equations that describe
• 29:32
  Speaker 1: it very simply, like F equals m A that ignores
• 29:35
  Speaker 1: a lot of the details of the particles that's going
• 29:37
  Speaker 1: on inside, or we do like really complicated calculations using
• 29:41
  Speaker 1: a computer to model all of those details and see
• 29:44
  Speaker 1: if we can describe the sort of big picture that
• 29:46
  Speaker 1: comes out. So far, we haven't found a simple set
• 29:48
  Speaker 1: of equations to describe supernova, and we don't have the
• 29:52
  Speaker 1: computing power necessary yet to like come up with a
• 29:55
  Speaker 1: basic model of the innards and understand how that describes
• 29:59
  Speaker 1: a supernova. So we're still really learning about how this
• 30:01
  Speaker 1: stuff works. So it sounds like if we want to
• 30:04
  Speaker 1: catch a supernova, we have to kind of stay frosty
• 30:07
  Speaker 1: and keep watching the sky, which I mean, we haven't
• 30:10
  Speaker 1: done that in like half an hour, so we should
• 30:12
  Speaker 1: probably take a break and check just to make sure
• 30:15
  Speaker 1: one hasn't happened while we've been talking, right, absolutely, all right,
• 30:32
  Speaker 1: I looked outside, bad news, not yet, and you might
• 30:38
  Speaker 1: wonder maybe Katie missed her supernova? Right. The amazing thing
• 30:41
  Speaker 1: about a supernova is that they're not just a flash
• 30:44
  Speaker 1: like they last for sometimes weeks or months. I mean,
• 30:47
  Speaker 1: there's sort of a flash on the cosmic time scale,
• 30:51
  Speaker 1: but for a human they can really last for quite
• 30:53
  Speaker 1: a long time. So if there's a supernova in the sky,
• 30:56
  Speaker 1: you could miss it today, you could miss it tomorrow.
• 30:58
  Speaker 1: You might even be able to ignore for a week
• 31:00
  Speaker 1: and then eventually look up and catch it up there
• 31:03
  Speaker 1: in the sky shining its photons at you. So it
• 31:06
  Speaker 1: seems like if we have like billions of observers, we
• 31:10
  Speaker 1: should catch it if it happens. And have we ever
• 31:14
  Speaker 1: caught one? So we have seen supernova and in fact,
• 31:16
  Speaker 1: they are so dramatic that you don't even have to
• 31:19
  Speaker 1: just look at Like the recent period of modern astronomy,
• 31:22
  Speaker 1: when we have space telescopes and incredible ground based telescopes
• 31:26
  Speaker 1: and all these new digital technologies to see supernova. People
• 31:30
  Speaker 1: have been seeing supernova in the sky for thousands of
• 31:34
  Speaker 1: years because sometimes they're just obvious. You know, if all
• 31:37
  Speaker 1: of a sudden there's an incredible bright new star in
• 31:40
  Speaker 1: the sky outshining everything else, then people are gonna see that,
• 31:44
  Speaker 1: and they're gonna say something to each other, and it's
• 31:46
  Speaker 1: gonna show up in historical records that people have done
• 31:49
  Speaker 1: a deep dive into the history of astronomy and found
• 31:53
  Speaker 1: times when locals have looked up in the sky and
• 31:55
  Speaker 1: seen something they didn't understand and wrote it down, and
• 31:57
  Speaker 1: we can now reinterpret those writings as evidence for supernova.
• 32:03
  Speaker 1: I can't imagine what I would be thinking like before.
• 32:06
  Speaker 1: I mean, I mean, if I saw a supernova today,
• 32:09
  Speaker 1: let's be honest, I would also be surprised and scared.
• 32:12
  Speaker 1: But back then even more so. If I didn't have
• 32:14
  Speaker 1: physicists like you telling me what was going on, I'd
• 32:17
  Speaker 1: probably think this guy was like really angry at me. Yeah,
• 32:22
  Speaker 1: it's hard to put yourself in the minds of these folks,
• 32:24
  Speaker 1: which is why it's really interesting to read these things,
• 32:27
  Speaker 1: like what does it mean for them? How do they
• 32:29
  Speaker 1: describe it what questions were they asking about this kind
• 32:32
  Speaker 1: of thing. It gives you not just a picture into
• 32:35
  Speaker 1: what supernovas are doing and how often they happened, but
• 32:38
  Speaker 1: also you know what people are doing, what they are thinking,
• 32:41
  Speaker 1: their relationship with the night sky itself super fun. So
• 32:46
  Speaker 1: how do we know? Because, like we we have a
• 32:49
  Speaker 1: history of things. We have written and drawn histories and
• 32:53
  Speaker 1: also oral histories. But there's a lot I think lost
• 32:56
  Speaker 1: in translation. And if someone described something, they're not going
• 32:59
  Speaker 1: to say, oh, saw a supernova last week it was
• 33:02
  Speaker 1: pretty cool. You know, They're going to describe it in
• 33:04
  Speaker 1: terms that they understand at the time. So how do
• 33:07
  Speaker 1: we know what they're describing is something like a supernova?
• 33:11
  Speaker 1: So we can't always know, but it depends on sort
• 33:13
  Speaker 1: of the quality of the notes that we're looking at.
• 33:15
  Speaker 1: And some of these things are a little speculative, and
• 33:17
  Speaker 1: in other cases people took really good notes and they
• 33:19
  Speaker 1: described something that we really can't otherwise explain. You know.
• 33:22
  Speaker 1: It's like, let's get into the details of the earliest
• 33:26
  Speaker 1: record we have that might be a supernova comes from
• 33:29
  Speaker 1: forty five hundred b C. This is like sixty hundred
• 33:34
  Speaker 1: years ago. Is a rock carving found in Kashmir in
• 33:38
  Speaker 1: India that people think depicts what is a hunting scene
• 33:41
  Speaker 1: with two very bright objects in the sky. The idea
• 33:45
  Speaker 1: is that it looks like a sky with two sons.
• 33:48
  Speaker 1: I mean, if you were out hunting in the old
• 33:50
  Speaker 1: days and saw a second son in the sky, you
• 33:53
  Speaker 1: might also be inspired to make a drawing of it.
• 33:56
  Speaker 1: So it's not exactly a hundred percent, but this might
• 33:59
  Speaker 1: be the least record of a supernova observation. And then
• 34:03
  Speaker 1: note taking now I am looking at this drawing and
• 34:06
  Speaker 1: it does look like two really bright suns in the
• 34:10
  Speaker 1: sky or or hear me out giant eyeball like eyeball
• 34:16
  Speaker 1: aliens with tentacles. Yeah, exactly. It's far from something you
• 34:19
  Speaker 1: would accept is like figure one in a scientific paper,
• 34:23
  Speaker 1: you know, But it's fun to think about what these
• 34:25
  Speaker 1: folks were imagining and what it was like for them,
• 34:28
  Speaker 1: Like was this so bright that they could see it
• 34:30
  Speaker 1: in the daytime? Itself? Like really a second son in
• 34:33
  Speaker 1: this guy, It's possible, you know. The most reliable ancient
• 34:37
  Speaker 1: recording of a supernova comes from Chinese astronomers. They noted
• 34:41
  Speaker 1: it in one five the appearance of a bright star
• 34:45
  Speaker 1: in the sky, and they observed that it took about
• 34:48
  Speaker 1: eight months to fade from the sky, and it sparkled
• 34:51
  Speaker 1: just like a star, and it didn't move like a comet.
• 34:55
  Speaker 1: And so this scene really matches what we expect from
• 34:58
  Speaker 1: a supernova. It's very bright, it doesn't move like a comet,
• 35:02
  Speaker 1: it sparkles like a star. It fades on the timescale
• 35:04
  Speaker 1: of weeks or months. So this very likely was a
• 35:07
  Speaker 1: supernova captured by those Chinese astronomers. So when they're looking
• 35:11
  Speaker 1: at this doesn't look like just kind of an extra
• 35:14
  Speaker 1: bright star or is it just astoundingly bright, like almost
• 35:19
  Speaker 1: having a little sun in the sky at night or something.
• 35:23
  Speaker 1: It depends exactly on where the supernova is, and so
• 35:27
  Speaker 1: if it's in another galaxy, remember that our galaxy is
• 35:30
  Speaker 1: like a hundred thousand light years across, but other galaxies
• 35:33
  Speaker 1: are millions of light years away. So if a supernova
• 35:37
  Speaker 1: happens in another galaxy, then that star is going to
• 35:40
  Speaker 1: go from invisible to visible at night. If it happens
• 35:43
  Speaker 1: in our galaxy, then the supernova is going to go
• 35:46
  Speaker 1: from like a star you can see at night to
• 35:48
  Speaker 1: a star you might be able to see in the daytime,
• 35:51
  Speaker 1: depending exactly on how close it is so yeah, this
• 35:54
  Speaker 1: could appear like a second son if a nearby star
• 35:58
  Speaker 1: goes supernova, because remember us, supernova can be as bright
• 36:01
  Speaker 1: as the entire galaxy. It can be a hundred billion
• 36:04
  Speaker 1: times brighter than our sun. Would we be in trouble?
• 36:08
  Speaker 1: Are there any stars that would cause us a little
• 36:11
  Speaker 1: bit of trouble here on Earth if it went supernova?
• 36:14
  Speaker 1: Oh yeah, if Proximus Centauri went supernova, we would be
• 36:17
  Speaker 1: quite literally toasted because the amount of energy and radiation
• 36:20
  Speaker 1: would really fry at least one half of the Earth,
• 36:23
  Speaker 1: you know, the half the Earth that was in the
• 36:25
  Speaker 1: direction of that star at the time. The rest of us,
• 36:28
  Speaker 1: having like an entire Earth shielding us from the supernova,
• 36:31
  Speaker 1: would probably be fine until, of course, the Earth's one
• 36:34
  Speaker 1: around and roasted the other half. So we're sort of
• 36:37
  Speaker 1: like rotisserie Earth. We just have to kind of like
• 36:40
  Speaker 1: all move to that side and keep moving, you know,
• 36:43
  Speaker 1: like hamsters and a hamster wheel of death. While I'll
• 36:47
  Speaker 1: be adding that to my long list of things that
• 36:50
  Speaker 1: I cannot directly change but cause me existential dreads so great.
• 36:55
  Speaker 1: It also sounds like a great pitch for a Netflix show.
• 36:58
  Speaker 1: You know, entire cities on wheels rolling around the planet
• 37:01
  Speaker 1: to avoid the frying radiation. Yeah, like snow piercer, but
• 37:06
  Speaker 1: except it's like to escape the heat. Supernova piercer sounds good.
• 37:12
  Speaker 1: And so if we look back in the historical record,
• 37:14
  Speaker 1: there's like five of these things observed in like the
• 37:17
  Speaker 1: last thousand years. There was a time in a thousand
• 37:20
  Speaker 1: and six when people all over the world noticed one,
• 37:23
  Speaker 1: from China to Japan. Astronomers in Iraq and Egypt and
• 37:27
  Speaker 1: also in Europe noticed something they called a guest star
• 37:30
  Speaker 1: which appeared sorry they called it a guest star. Yeah,
• 37:34
  Speaker 1: like we have a sudden guest somebody said, another place
• 37:37
  Speaker 1: for dinner, welcome or not. I do like the idea
• 37:40
  Speaker 1: of like just on one of these night shows, you know,
• 37:43
  Speaker 1: Jimmy Fallon or whoever, it's like, oh, we got a
• 37:45
  Speaker 1: guest star, and then it's a supernova and everyone gets
• 37:48
  Speaker 1: fried exactly. Sometimes they just blow it all up. And
• 37:51
  Speaker 1: then as we enter in sort of like the more
• 37:53
  Speaker 1: modern historical period, we have folks whose names we know
• 37:57
  Speaker 1: well writing about these things. So Tico Bray noted one
• 38:01
  Speaker 1: in fifteen seventy two in the sky and took a
• 38:04
  Speaker 1: lot of great data. He's sort of famous for taking
• 38:06
  Speaker 1: meticulous notes about what he saw. What's interesting also about
• 38:10
  Speaker 1: this one is, like we said earlier, it helps us
• 38:12
  Speaker 1: think about what people thought about supernova at the time
• 38:15
  Speaker 1: and Europe around this time. Most people thought that the
• 38:18
  Speaker 1: cosmos beyond the moon and the planets couldn't change. They
• 38:22
  Speaker 1: thought it was just like out there static. You know,
• 38:24
  Speaker 1: the whole universe was a bunch of stars hung out
• 38:27
  Speaker 1: into space. They weren't even aware of the idea of
• 38:30
  Speaker 1: other galaxies, right. They thought the whole universe was infinitely old,
• 38:34
  Speaker 1: with stars not moving or changing. That was the idea
• 38:37
  Speaker 1: at the time, just kind of painted on a big
• 38:40
  Speaker 1: globe or something. Yeah, so this didn't really fit well
• 38:43
  Speaker 1: with the idea of supernova because this is like a
• 38:45
  Speaker 1: change in something. So they thought that probably of something
• 38:48
  Speaker 1: happening in the atmosphere. They thought supernovas were like weird
• 38:52
  Speaker 1: bright lights created like, you know, fifty miles above the surface,
• 38:56
  Speaker 1: instead of super duper far away swamp gas. Well ali exactly.
• 39:01
  Speaker 1: But you know, Bray took a lot of notes, and
• 39:03
  Speaker 1: he realized that this thing remains stationary from night tonight,
• 39:07
  Speaker 1: doesn't change. It's parallax, and so it has to be
• 39:10
  Speaker 1: really really far away, and so he wrote a book
• 39:13
  Speaker 1: with all of these details, and it's that book which
• 39:15
  Speaker 1: gave the name nova to things that appear in the
• 39:17
  Speaker 1: night sky. But then the last one that we've ever
• 39:20
  Speaker 1: seen coming from our galaxy was Kepler. He saw one
• 39:24
  Speaker 1: in sixteen o four, And so you know, here we
• 39:26
  Speaker 1: have to make a distinction. We are seeing supernova from
• 39:29
  Speaker 1: all over the universe because they are so bright that
• 39:32
  Speaker 1: we can also see them from other galaxies, but the
• 39:35
  Speaker 1: one we saw in sixteen o four was the last
• 39:37
  Speaker 1: one we've ever seen from the Milky Way itself. So
• 39:42
  Speaker 1: I haven't necessarily been keeping good track of the dates,
• 39:45
  Speaker 1: but had we been seeing them at a rate greater
• 39:49
  Speaker 1: than once every four hundred years before this point or no.
• 39:54
  Speaker 1: So we have some estimates for how likely it is
• 39:56
  Speaker 1: to create supernovas from watching other galaxies and from think
• 40:00
  Speaker 1: about the ones we've seen in our galaxy, and so
• 40:03
  Speaker 1: we estimate that in the Milky Way we should get
• 40:05
  Speaker 1: about one supernova every twenty years or so. The galaxy
• 40:09
  Speaker 1: of about a hundred billion stars should give us a
• 40:12
  Speaker 1: supernova every twenty years. So in the four hundred years
• 40:15
  Speaker 1: since Kepler's observation, we should have seen about twenty supernova
• 40:19
  Speaker 1: in the Milky Way, right, and you mentioned that we
• 40:22
  Speaker 1: saw like potentially saw like five in the past one
• 40:26
  Speaker 1: thousand years, So that'd be one every two hundred years, right,
• 40:30
  Speaker 1: not one every four hundred years. That's right. But we
• 40:33
  Speaker 1: don't think that the historical record is complete, right. We
• 40:36
  Speaker 1: don't think that we have found every written record of supernovas,
• 40:40
  Speaker 1: and also we don't think that people have seen all
• 40:42
  Speaker 1: the supernovas that were out there. But something we'll dig
• 40:45
  Speaker 1: into in a minute is like how often we expect
• 40:47
  Speaker 1: these things to happen, and how likely we are to
• 40:50
  Speaker 1: see one if it does happen in our galaxy. Right,
• 40:53
  Speaker 1: So we have this mystery of these missing supernovas, right
• 40:58
  Speaker 1: that if like we should be seeing one every maybe
• 41:01
  Speaker 1: twenty years, or at least more frequently than every four years.
• 41:06
  Speaker 1: But before we waste time trying to figure it out,
• 41:09
  Speaker 1: just a case it popped up while in the past,
• 41:13
  Speaker 1: like you know, fifteen minutes while we were discussing, I'm
• 41:15
  Speaker 1: gonna go out and check again, just make sure, because
• 41:18
  Speaker 1: then that that would settle it. Right. I'm so impressed
• 41:21
  Speaker 1: with how dutiful you are as a researcher. Yeah, yeah,
• 41:24
  Speaker 1: I'm gonna get up on the roof and stare right
• 41:27
  Speaker 1: into the sun for a little while. I will be
• 41:29
  Speaker 1: right back. Well, I am back. I stared right into
• 41:45
  Speaker 1: the sky directly at the Sun just so I wouldn't
• 41:48
  Speaker 1: miss the supernova if it happened, and I gotta tell
• 41:51
  Speaker 1: you was not one of my best ideas. I'm glad
• 41:54
  Speaker 1: that you're still back and you have everything you need
• 41:56
  Speaker 1: to continue podcasting, because you know, we don't really need
• 41:59
  Speaker 1: your eyeballs for podcast. Yes, the uh. I basically just
• 42:03
  Speaker 1: see a big glowing orb all the time, which is great.
• 42:07
  Speaker 1: So we were talking about there is this mystery because
• 42:11
  Speaker 1: it seems like we should be seeing these supernovas more often.
• 42:14
  Speaker 1: Not only in historical records, does it seem like there
• 42:17
  Speaker 1: were more supernovas, you know, not maybe one every two
• 42:21
  Speaker 1: hundred years or so, not one every four hundred years,
• 42:23
  Speaker 1: but also there was a calculation done to see how
• 42:27
  Speaker 1: often should we be seeing it, and that resulted in
• 42:31
  Speaker 1: about twenty years, right exactly. And remember we don't understand
• 42:35
  Speaker 1: supernovas very well, so it's hard to predict, sort of theoretically,
• 42:38
  Speaker 1: how often they should happen. But we can learn by
• 42:40
  Speaker 1: looking at all the other galaxies to try to get
• 42:43
  Speaker 1: a sense for the rate of supernovas. So remember, we
• 42:46
  Speaker 1: can see supernovas in our galaxy even just using the
• 42:49
  Speaker 1: naked eye, going back thousands of years. But in the
• 42:52
  Speaker 1: more recent era, because we have telescopes, we could now
• 42:54
  Speaker 1: study very thoroughly supernovas in other galaxies. So, starting in
• 42:59
  Speaker 1: the nine or so, people began these campaigns to scan
• 43:02
  Speaker 1: the sky for new stars appearing in other galaxies using telescopes,
• 43:07
  Speaker 1: and they saw dozens and so we have definitely seen
• 43:10
  Speaker 1: supernovas recently. For example, we saw one in seven that
• 43:15
  Speaker 1: came from a large Magellanic cloud. This was one you
• 43:18
  Speaker 1: could actually see with the naked eye, even though it
• 43:20
  Speaker 1: wasn't in the Milky Way, because a large Magellanic cloud
• 43:23
  Speaker 1: is a satellite of the Milky Way, so it wasn't
• 43:25
  Speaker 1: that far away. So we're seeing supernovas in other galaxies,
• 43:30
  Speaker 1: and that lets us estimate what we think is the
• 43:32
  Speaker 1: rate of supernovas we should expect in the Milky Way,
• 43:36
  Speaker 1: being about one every twenty years. You know, there's still
• 43:39
  Speaker 1: a lot of uncertainty in that number, and so then
• 43:41
  Speaker 1: the question is, you know, are they not happening in
• 43:44
  Speaker 1: the Milky Way, or are we just not seeing them,
• 43:47
  Speaker 1: are they hiding it from us? Or maybe the Milky
• 43:50
  Speaker 1: Way is super weird and doesn't make supernovas as often
• 43:54
  Speaker 1: as these other neighboring galaxies. Right these are like just
• 43:57
  Speaker 1: the basic questions we have about supernove is because we're
• 44:01
  Speaker 1: so clueless about the thing that triggers them, the moment
• 44:04
  Speaker 1: that the star decides to collapse, and exactly what's going
• 44:07
  Speaker 1: on inside. I mean, it seems odd though, for like
• 44:11
  Speaker 1: an entire galaxy to have different rules from another galaxy,
• 44:17
  Speaker 1: or is that not so odd? It would be odd,
• 44:19
  Speaker 1: But there are odd galaxies out there. There are galaxies
• 44:22
  Speaker 1: that have lots of dark matter and galaxies that have
• 44:24
  Speaker 1: very little dark matter. They're huge galaxies and little galaxies.
• 44:27
  Speaker 1: There are galaxies that are still making stars and galaxies
• 44:30
  Speaker 1: that are quenched that will no longer be producing stars.
• 44:33
  Speaker 1: And we just don't know if the Milky Way is
• 44:36
  Speaker 1: typical or not, the same way we don't know if
• 44:38
  Speaker 1: Earth is typical or if it's weird and rare in
• 44:41
  Speaker 1: the universe. These are the kind of questions we get
• 44:44
  Speaker 1: to ask as we look out deep into the universe
• 44:47
  Speaker 1: to try to figure out whether our context is normal
• 44:50
  Speaker 1: or really really weird. But we can do more than
• 44:53
  Speaker 1: just look for supernovas as they happen. We can actually
• 44:56
  Speaker 1: also look for supernovas that have happened that we might
• 44:59
  Speaker 1: have missed because we can see supernova remnants. When a
• 45:03
  Speaker 1: supernova happens, it's very bright, it's very dramatic, but also
• 45:06
  Speaker 1: it creates this shock wave that shoots out into the universe,
• 45:10
  Speaker 1: leaving a sort of interesting fingerprint that you can continue
• 45:13
  Speaker 1: to see four hundreds or thousands of years later. So
• 45:17
  Speaker 1: it's kind of like looking at a star's kind of
• 45:19
  Speaker 1: fossil record exactly. Because when a supernova happens, remember, it
• 45:23
  Speaker 1: shoots out like several solar masses worth of stuff, right, Like,
• 45:28
  Speaker 1: think about what that means. A solar mass is an
• 45:31
  Speaker 1: entire sun's worth of stuff. And so now you have
• 45:33
  Speaker 1: a supernova shooting out like several times the mass of
• 45:37
  Speaker 1: the Sun, just in plasma and hot gas out into
• 45:40
  Speaker 1: the universe and incredibly high speeds, like significant fractions of
• 45:45
  Speaker 1: the speed of light. So what happens is that it's
• 45:47
  Speaker 1: going to smash into all the stuff around it. Space
• 45:50
  Speaker 1: is not totally empty, it's filled with the interstellar medium.
• 45:53
  Speaker 1: Which is like a very dilute gas, but when the
• 45:56
  Speaker 1: supernova remnants smash into it, you get this expanding shell
• 46:00
  Speaker 1: of a shock wave. So that's what we call a
• 46:02
  Speaker 1: supernova remnant. It's very distinctive. And scientists have looked out
• 46:06
  Speaker 1: into the night sky and for example, in our galaxy
• 46:09
  Speaker 1: in Cassiopeia, they see a remnant which looks to be
• 46:13
  Speaker 1: about three hundred and twenty five years old, which means
• 46:17
  Speaker 1: they think there was a supernova there three hundred years
• 46:20
  Speaker 1: ago that everybody missed. Nobody saw it, but we can
• 46:23
  Speaker 1: see evidence that had happened, and it happened fairly recently,
• 46:27
  Speaker 1: so it's a It's an interesting thing because like as
• 46:30
  Speaker 1: kind of postmortem detectives of this star explosion, you can't
• 46:35
  Speaker 1: necessarily look just at the sight of where the star was.
• 46:39
  Speaker 1: You're looking at where the remnants go, right, So it's
• 46:42
  Speaker 1: this expanding force. It's not just like looking at where
• 46:47
  Speaker 1: the star died. You have to look far afield of
• 46:50
  Speaker 1: where the star has exploded to yeah, precisely. And this
• 46:53
  Speaker 1: stuff moves out, but it moves out much slower than
• 46:56
  Speaker 1: the speed of light. You know, it's pretty fast and
• 46:58
  Speaker 1: pretty energetic, but it sort of in the vicinity of
• 47:01
  Speaker 1: where it happened. It's not like looking at black hole collisions,
• 47:05
  Speaker 1: and we're getting evidence of that from gravitational waves that
• 47:08
  Speaker 1: travels at the speed of light directly to us. Now
• 47:10
  Speaker 1: we're looking at like stuff spewing out sideways from the
• 47:13
  Speaker 1: supernova ramming into something else and then sending us light
• 47:17
  Speaker 1: from that collision. So we're seeing this like shock wave
• 47:21
  Speaker 1: emanate from the supernova, and we're seeing light from that
• 47:24
  Speaker 1: shock wave as it bounces into gas and heats it up.
• 47:28
  Speaker 1: So it's pretty cool. You can tell that as supernova
• 47:30
  Speaker 1: was there. It's sort of like you missed an explosion,
• 47:32
  Speaker 1: but now you're looking at the burn marks on the
• 47:34
  Speaker 1: ground or something like that. Yeah, yeah, that's really interesting. Yeah,
• 47:38
  Speaker 1: and people have done scans for these kind of remnants
• 47:41
  Speaker 1: in our galaxies and they found a few. They found
• 47:44
  Speaker 1: this one in Cassiopeia. That found another one that they're
• 47:46
  Speaker 1: pretty sure happened at the end of the nineteenth century.
• 47:49
  Speaker 1: But you know, there's no records that anybody saw the
• 47:52
  Speaker 1: actual supernova. So all this kind of stuff lends credence
• 47:55
  Speaker 1: to the idea that maybe supernova's actually are happening in
• 47:59
  Speaker 1: our galaxy. We're just not seeing them right that they're
• 48:02
  Speaker 1: out there, they're blowing up, but we are missing the party.
• 48:06
  Speaker 1: But wait just a minute, because you said that they're
• 48:09
  Speaker 1: super bright. There's a lot of energy released, and our
• 48:13
  Speaker 1: galaxy isn't you know, too far away from us. So
• 48:16
  Speaker 1: how could we miss that? Did we podcast over it? This?
• 48:20
  Speaker 1: This is what I was worried about. It's because you
• 48:23
  Speaker 1: were napping. You know, you took a break, a nap
• 48:26
  Speaker 1: in a coffee, and you missed all the important datah
• 48:29
  Speaker 1: man I got like fomo on a galactic scale. Now, no, no,
• 48:33
  Speaker 1: don't feel bad. It's not because we're lazy. The issue,
• 48:36
  Speaker 1: like everything else, is probably location. You know, the galaxy
• 48:39
  Speaker 1: is not that big on a universal link scale, but
• 48:42
  Speaker 1: it's also not that transparent. You know, the galaxy is
• 48:45
  Speaker 1: a lot of gas and dust in it, and if
• 48:48
  Speaker 1: something happens on the other side of the galaxy, then
• 48:51
  Speaker 1: the center of the galaxy, which is a swirling maelstrom
• 48:54
  Speaker 1: of intensity and gas and dust and it's pretty opaque,
• 48:57
  Speaker 1: then we might not be able to see it. And
• 49:00
  Speaker 1: so some of these things might just be happening behind
• 49:02
  Speaker 1: big dust clouds or big gas clouds, and this dust
• 49:06
  Speaker 1: is really good at blocking the light. And unfortunately, the
• 49:10
  Speaker 1: places that have the most dust are the densest places,
• 49:13
  Speaker 1: which are also the places that supernova are most likely
• 49:17
  Speaker 1: to happen. So this really was a punishment for us
• 49:20
  Speaker 1: not cleaning our rooms. I knew it it might be.
• 49:24
  Speaker 1: You know, this is still really speculative. Is the kind
• 49:27
  Speaker 1: of explanation people are trying to understand if it works.
• 49:30
  Speaker 1: And I read a paper last week exploring this in detail,
• 49:33
  Speaker 1: trying to say, like, can we explain not having seen
• 49:36
  Speaker 1: supernova based on where the gas and dust are in
• 49:40
  Speaker 1: the galaxy? And they did a really interesting, very thorough study.
• 49:44
  Speaker 1: They have a model for where they think supernova should
• 49:47
  Speaker 1: happen based on where are the stars in the galaxy.
• 49:50
  Speaker 1: From that they get a sense for how much light
• 49:52
  Speaker 1: should have arrived on Earth from each of these supernova,
• 49:55
  Speaker 1: you know, how bright it was, how far away it was.
• 49:58
  Speaker 1: Then we have maps actually of where or the dust
• 50:00
  Speaker 1: is in the galaxy, right like where these clouds of
• 50:04
  Speaker 1: choking gas and dust that would obscure our view are sitting.
• 50:07
  Speaker 1: And then we can do a calculation and say where
• 50:10
  Speaker 1: do we expect to see supernova in our galaxy? And
• 50:13
  Speaker 1: where do we expect not to see them because the
• 50:16
  Speaker 1: gas and dust are blocking them, and drum roll, do
• 50:19
  Speaker 1: we have those results. We do have those results. I'm
• 50:21
  Speaker 1: looking at them right now from this paper, and interestingly,
• 50:25
  Speaker 1: the results are kind of a surprise. Most of the
• 50:28
  Speaker 1: supernova that we have seen in our galaxy actually land
• 50:33
  Speaker 1: in places where we didn't expect to see them because
• 50:36
  Speaker 1: either there actually was a lot of gas and dust,
• 50:38
  Speaker 1: which somehow they are mysteriously overpowering, or it's a place
• 50:41
  Speaker 1: where you don't expect to see many supernovas. So we
• 50:44
  Speaker 1: like saw a super rare supernova. It's not something that
• 50:47
  Speaker 1: we understand, and so it's the kind of moment in
• 50:50
  Speaker 1: science where we go, well, that didn't work. You know,
• 50:53
  Speaker 1: we have this data, have a basic model that doesn't
• 50:56
  Speaker 1: explain it. What's wrong? Probably something simple is wrong with
• 51:00
  Speaker 1: our model, our estimate of how often the supernova happen,
• 51:04
  Speaker 1: or our guests for where the dust is or how
• 51:07
  Speaker 1: transparent that dust is to the light from the supernova.
• 51:11
  Speaker 1: Something is going wrong with these models. But the upshot
• 51:14
  Speaker 1: is that we can't explain it. We do not understand
• 51:16
  Speaker 1: why we are seeing the supernova that we are seeing
• 51:19
  Speaker 1: and why we are not seeing supernova in some areas
• 51:22
  Speaker 1: of the galaxy. So the model was saying not necessarily
• 51:26
  Speaker 1: that the supernova was in the location where it couldn't happen,
• 51:31
  Speaker 1: but that it was unlikely for us to be able
• 51:33
  Speaker 1: to see it at this location. Some of the ones
• 51:36
  Speaker 1: that we have seen are happening in places where they
• 51:39
  Speaker 1: should be very very rare. Not impossible, but you know,
• 51:42
  Speaker 1: you should expect to see more supernova where there are
• 51:45
  Speaker 1: more stars. And if you look at the historical distribution
• 51:48
  Speaker 1: of supernova that we have seen in our galaxy, there's
• 51:51
  Speaker 1: a lot of them in places where there aren't very
• 51:54
  Speaker 1: many stars, which is kind of confusing. Are supernova more
• 51:57
  Speaker 1: likely to happen there, or maybe there's some structure to
• 52:01
  Speaker 1: the galaxy that we haven't described in our model, you know,
• 52:04
  Speaker 1: some like clusters of gas and dust that are creating
• 52:08
  Speaker 1: supernovas or blocking supernovas. Something else is missing from our
• 52:12
  Speaker 1: model to add to this recipe to give us a
• 52:14
  Speaker 1: depiction that matches what we actually see out there in
• 52:17
  Speaker 1: the night sky. Yeah, that's really interesting. Like I wonder
• 52:21
  Speaker 1: if it could even be something like, you know, if
• 52:23
  Speaker 1: a star that's more likely to go supernova is more
• 52:27
  Speaker 1: likely to be a loner. It could be because we
• 52:30
  Speaker 1: know also that there's a lot of difference in sort
• 52:33
  Speaker 1: of the wrong ingredients in the galaxy. You know, in
• 52:36
  Speaker 1: the center of the galaxy there are more heavy metals,
• 52:39
  Speaker 1: so the stars there are more metallic, and so the
• 52:41
  Speaker 1: galactic conditions are very different in the center of the
• 52:44
  Speaker 1: galaxy and the spiral arms, and then above the galactic plane.
• 52:48
  Speaker 1: So this is the kind of next round of research
• 52:50
  Speaker 1: is understanding, like what are the conditions to make supernova?
• 52:54
  Speaker 1: What are the conditions in the galaxy? Can we make
• 52:56
  Speaker 1: a model that explains why you might be getting more
• 52:59
  Speaker 1: supernova or maybe just why we're not seeing them? You know,
• 53:02
  Speaker 1: maybe this more structure to this gas and dust than
• 53:04
  Speaker 1: we thought we understood. But it's a great opportunity. Every
• 53:07
  Speaker 1: time you have something you don't understand is a chance
• 53:10
  Speaker 1: to refine your models and learn something new about the universe.
• 53:13
  Speaker 1: Maybe it's just something about the map of the gas
• 53:15
  Speaker 1: and dust, or you know, maybe like the discoveries of
• 53:18
  Speaker 1: dark matter, this is not something that we can resolve
• 53:21
  Speaker 1: with like a little tweak to our models. Maybe it's
• 53:23
  Speaker 1: gonna require something really big and new in our understanding
• 53:27
  Speaker 1: of the universe. Right, so you gotta double and maybe
• 53:30
  Speaker 1: even triple. Check your mouth first, make sure someone didn't
• 53:34
  Speaker 1: just forget to carry a one. And then maybe it's
• 53:37
  Speaker 1: a sign of some really interesting discovery or mystery about
• 53:42
  Speaker 1: the universe. And now we are lucky enough to have
• 53:44
  Speaker 1: other ways to see supernova, not just through light. Supernova
• 53:49
  Speaker 1: also produce a lot of radiation in new trinos for example,
• 53:53
  Speaker 1: In fact, most of the energy produced in a supernova
• 53:56
  Speaker 1: comes from new trinos something like that. The radiation from
• 54:01
  Speaker 1: the supernova is in the form of neutrinos, which are
• 54:04
  Speaker 1: these weird little particles that mostly pass through matter, ignoring us.
• 54:09
  Speaker 1: And in the supernova, we actually saw the new trinos
• 54:13
  Speaker 1: from the supernova first because they're produced at the heart
• 54:16
  Speaker 1: of the supernova. But then they fly right out through
• 54:19
  Speaker 1: the craziness and get to Earth before the photons do,
• 54:22
  Speaker 1: because the photons have to make their way sort of
• 54:24
  Speaker 1: through the star before they get to the surface and
• 54:26
  Speaker 1: can get emitted. So neutrinos are a new way to
• 54:30
  Speaker 1: see supernova. So now we have like new kinds of
• 54:32
  Speaker 1: supernova eyeballs, so that even when you're nappying, Katie, we
• 54:36
  Speaker 1: are watching the sky for supernovas. Thank you. That does
• 54:39
  Speaker 1: make me feel a little more relaxed. So I guess
• 54:42
  Speaker 1: you use some kind of like neutrino glasses so that
• 54:45
  Speaker 1: you can see these If these are not actual visible
• 54:48
  Speaker 1: light particles, Yeah, you cannot see new grina's very easily.
• 54:52
  Speaker 1: But particle physicists have neutrino experiments deep underground to try
• 54:56
  Speaker 1: to understand how neutrinos changed from one kind due to another,
• 54:59
  Speaker 1: or to do other kinds of neutrino experiments. We recently
• 55:03
  Speaker 1: did a whole episode about how neutrinos can teach us
• 55:06
  Speaker 1: about supernova, so go check that out. But one of
• 55:08
  Speaker 1: my favorite facts about neutrinos is that they used it
• 55:11
  Speaker 1: to take a picture of the Sun. Remember, neutrinos interact
• 55:15
  Speaker 1: very very rarely with us, but there's huge numbers of them,
• 55:18
  Speaker 1: Like a hundred billion neutrinos from our sun passed through
• 55:22
  Speaker 1: your fingernail every second. But you're lucky if you can
• 55:25
  Speaker 1: even detect one in a huge specialized device. So they
• 55:29
  Speaker 1: pointed this thing at the Sun for like months and
• 55:32
  Speaker 1: they got a picture of the Sun in neutrinos, which
• 55:34
  Speaker 1: is is kind of cool because it's like another way
• 55:37
  Speaker 1: to see the Sun. I just get really excited every
• 55:39
  Speaker 1: time humans build another kind of eyeball to look out
• 55:41
  Speaker 1: into the universe. I'm guessing though, like neutrino glasses that
• 55:45
  Speaker 1: I can wear and look and spot neutrinos myself are
• 55:48
  Speaker 1: a little bit far from the market, maybe another ten
• 55:52
  Speaker 1: years or so. Yeah. Currently these things have like thousands
• 55:56
  Speaker 1: of tons of heavy water in them, And so unless
• 55:59
  Speaker 1: you're very strong or willing to put on extremely large
• 56:03
  Speaker 1: glasses and you're not going to be seeing neutrinos with
• 56:06
  Speaker 1: your eyeballs. I'll work on my neck exercises. But in
• 56:10
  Speaker 1: the meantime, the universe continues to churn and burn, and
• 56:13
  Speaker 1: supernovas are happening out there, blowing out these incredible cosmic
• 56:17
  Speaker 1: engines of the night sky. You know, we are grateful
• 56:20
  Speaker 1: that stars last for as long as they do, that
• 56:23
  Speaker 1: they balance on this nice edge between gravity and fusion
• 56:26
  Speaker 1: for so many billion years to light up the night
• 56:29
  Speaker 1: sky and to provide life here on Earth, and just
• 56:32
  Speaker 1: to provide us with something nice to look at as
• 56:35
  Speaker 1: we shiver in front of the fire and sip our
• 56:37
  Speaker 1: hot coco on our camping trips. But eventually those stars
• 56:41
  Speaker 1: do give up their life and they do go out
• 56:43
  Speaker 1: in incredible cosmic explosions, which then give us another opportunity
• 56:47
  Speaker 1: to learn what's going on inside the heart of those stars.
• 56:51
  Speaker 1: And so the more things blow up, the more we
• 56:53
  Speaker 1: learn about them. A bunch of drama queens. So if
• 56:58
  Speaker 1: you're out there interested in supernova, to keep an eye
• 57:00
  Speaker 1: on the night sky. You might see one with the
• 57:02
  Speaker 1: naked eye. Or if you're excited about squirrels, keep watching
• 57:06
  Speaker 1: to see how many acorns they eat. Maybe you'll see
• 57:08
  Speaker 1: you one of those blow up. I do not endorse
• 57:12
  Speaker 1: that message. Well, thanks Katie very much for joining us
• 57:16
  Speaker 1: on this tour of cosmic catastrophes. Thanks for having me,
• 57:20
  Speaker 1: and thank you all for listening. Tune in next time.
• 57:30
  Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
• 57:33
  Speaker 1: the Universe is a production of I Heart Radio. Or
• 57:36
  Speaker 1: more podcast from my Heart Radio, visit the I Heart
• 57:39
  Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your
• 57:43
  Speaker 1: favorite shows.