Dr. Kirk Transcript
Victoria:
Our guest this week is Dr. Michael Kirk. He is a research scientist and the heliophysics science division at NASA’s Goddard Space Flight Center with Astra LLC. He’s working in support of the Solar Dynamics Observatory satellites, studying the physics of the Sun, the causes of solar variability, and its impact on Earth.
Dr. Kirk received his PhD in astronomy from New Mexico State University and his bachelor’s degree from Whitman College in Washington State. He first worked at Goddard Space Flight Center in 2007 as a systems engineer researching the changing position and size of the polar coronal holes throughout the solar cycle.
Outside of work, he enjoys discovering new music and experimenting with home roasting coffee.
This week’s questions were submitted by the listeners through emails and on social media and by students at the Montessori school of Denver in Denver, Colorado.
Dr. Kirk, thank you so much for talking to us today.
Dr. Kirk:
It’s a pleasure to be here. I’m so happy to be here talking with you about the Sun, one of my most favorite topics, and as well as asking, you know, good questions for you to think about. Because you know, that’s what every good scientist does is they generate more questions.
Victoria:
(David – Why is the sun so bright?)
Yes. All right. With that, we can start with the questions. This first question is from David. Why is the Sun so bright?
Dr. Kirk:
Yeah, that is a fantastic question. And it might sound like a really straightforward question, like why is it, right? There are so much complicated physics that go into it. So I’m going to just give you a brief overview because like everything else in science there is so much more under the surface.
So. Why is the Sun so bright? Well, it’s a giant nuclear reaction happening all the time. Okay. So what that means is that we have hot hydrogen in the Sun, and it’s being squished together under extreme temperature and pressures as forming helium. And in that process of taking two hydrogen atoms and squishing them together and forming helium, it releases energy. And it releases a lot of energy, and that energy is all generate in the core of the Sun and then slowly percolates up to the surface of the Sun and then radiates out into space. And so what we’re seeing is just a very small piece of that nuclear energy that’s generated at the core of the Sun and then comes out and hits us.
Victoria:
(Elliot – Why do we have outer space?)
That is very cool. This question is from Elliot. Elliot wants to know why we have outer space.
Dr. Kirk:
Oh Elliot, that’s an insightful question. Because there’s an outer space, there’s gotta be an inner space, right? Okay. So what’s the inner and outer here. Okay. So what outer space is everything outside the Earth’s atmosphere. So the Earth’s atmosphere extends several hundred kilometers above the surface. And at some point, the Earth’s atmosphere dissipates to nothing. So there’s no more air: there’s no more air to breathe; there’s no more oxygen; there’s no more wind; there’s no more clouds. And once you get beyond that point, that’s what we call outer space. Everything inside with the Earth’s atmosphere, with the sky, with clouds, with, you know, birds flying, all that would be inner space. Or that’s just normal for us, so we don’t actually call it anything different. So that’s the differences between outer space and what normal is. So outer space doesn’t have air in it. That’s the biggest difference.
Victoria:
(Kiera – Have you been to outer space?)
Awesome. Okay. Kiera wants to know, have you ever been to outer space?
Dr. Kirk:
I have not been to outer space, but it’s certainly on my bucket list. I mean, if I had to think of one of the coolest places to go, it would be up high enough in the atmosphere of the Earth or just outside the atmosphere. So you could see the entire Earth. I would think that’s amazing. So I don’t know, with commercial space flight, maybe I’ll get a chance to go one of these days.
Victoria:
(Alisha – Would you go to the Sun if there was a spaceship that could?)
(John – How close would people ever be able to get to the Sun if we could travel to it?)
That would be awesome. This next, actually this is a pair of questions that’s next. The first question is from Alisha, would you go to the Sun if there was a spaceship that could? And John wants to know, how close would people ever be able to get to the Sun if we could travel to it?
Dr. Kirk:
So both of those questions, it’s about whether we can go to the Sun, is so incredibly topical for this exact moment in time. It’s like they had been absorbing all of the latest solar physics material coming out in publications. I mean, this is a fantastic.
Okay. So, what I mean is that NASA, not that long ago, just a couple of years ago, sent a probe to the Sun. It’s called Parker Solar Probe. And this probe is flying closer to the Sun than we have ever flown before. One of the features on that spacecraft, it just, there’s no people on board, of course, right. This is just cameras and other sensors on board. But one of the features on board is a brand new heat shield. And this is like brand new technology. This heat shield is so good that you could take a blowtorch and put it on one side of the heat shield and put your hand on the other side of the heat shield and your hand feels no heat at all. It doesn’t feel like anything. So you know, blowtorch just blasting away at that heat shield, and you feel nothing. So this heat shield is brand new technology. It’s this carbon foam kind of a thing. It’s super cool. I got to pick up a chunk once and this chunk was probably about the size of, Oh, I don’t know an encyclopedia or like a really large book, and it weighed nothing. It was just like feather light. It was yeah, crazy stuff. Okay.
This heat shield though, is the piece of technology that made it possible for this spacecraft to go to the Sun. So, if in the future, at some point, like, I don’t know, maybe a hundred years, 200 years in the future, we could wrap a spaceship with that same sort of heat shield, we could fly a spaceship. There are people on it to the Sun, to the outer atmosphere of the Sun.
That being said, would I want to go, not really. It’s really hot there. It’s not exactly a friendly place to visit. The outer atmosphere of the Sun is over a million degrees in temperature. And so it’s not someplace that humans would ever really want to hang out for any length of time. Not only where we had just talked about it, the sun’s really bright and it’s extremely hot. And you’re going to have to sit behind a heat shield, this crazy heat shield, in order to protect yourself. And so you wouldn’t be able to look at the Sun at all directly. And so you’d only be able to look at space. So I’d rather go someplace else, not to the Sun, if I was going to travel. But if people were to develop that spaceship, yeah, we could definitely do it. We could definitely go to the Sun.
Victoria:
Wow. That would be cool. But I agree, I don’t think I would want to go.
Dr. Kirk:
No, that’s just, I don’t know. I mean, there are a lot of cool places in the solar system, a lot of places that are much higher on my list to go to than the Sun.
Victoria:
(Richie – How do you study the Sun?)
Okay. This next question comes from Richie. How do you study the Sun?
Dr. Kirk:
That’s a great question. Cause the sun’s really bright, you can’t look at it directly. And gosh, you should never use binoculars or a telescope to look directly at the Sun unless you have a special filter for it. But that’s how we study it. As we have these special filters that we’ve built for telescopes to look directly at the Sun.
So NASA has a fleet of spacecraft, several space craft around in Earth’s orbit and around the orbit of the Sun, that all had these special cameras to look at the Sun directly. And these are really highly specialized camera. They actually don’t look at the Sun in visible light, the light that you see with your eyes. They look at the Sun in extreme ultraviolet light. So ultraviolet light is like the light that gives you sunburns. So it’s the same kind of ultraviolet light. We look at a very specific section of it, that’s the short wavelengths of light and use that to study the Sun.
Then there’s a whole another fleet of observatories that are on the grounds. And so these are our ground-based observatories, like you look at other stars with, except we study the Sun, which is our closest star. Again, we have to develop really specialized filters, filters that filter out like 99.9% of the light before we can actually see the surface of the Sun, because it’s so bright and it’s so hot. Otherwise you just burn up anything.
So there’s this one time that they had the mirrors misaligned in a ground based telescope. So this is a telescope in, I think it was in Arizona. And the mirrors were not quite aligned right. And so instead of the light being directed through the filter, it bounced out into the observatory itself. And there’s still a mark on the wall from where the light burned through the wall, the concrete and steel wall. So yeah, it is dangerous stuff, but that’s why we have these good filters to be able to filter out most of the light.
Victoria:
(Nicholas and Elliot – Why is it bad to look at the Sun?)
Yikes! I think that pretty much answers the next question that you can add something to it if you want. This question we had submitted by two different listeners, both Nicholas and Elliot want to know, why is it bad to look at the Sun?
Dr. Kirk:
Yeah, well. Your eyes are really sensitive. So one of the cool things that I’ve learned when I was in school was that your eyes are so sensitive it can detect just a couple of photons of light. So like a couple little particles of light. Your eyes are that sensitive. If you get dark adjusted, sitting in a dark room, and you see just a few photons come out and hit your eye, your eyes can detect it. So our eyes are built to detect very small amounts of light.
The Sun is the opposite of that. There are so many photons, there’s so much light coming down. It would completely burn your eye, where you would go blind if you look directly at the Sun. So that’s why you need either special glasses or special filters for your camera or a special filter for your telescope to ever look at the Sun directly.
Victoria:
(Fynn – Why is it warm in the Sun?)
That makes sense. Okay. Another I think good follow-up question to that. Fynn wants to know, why is it warm in the Sun?
Dr. Kirk:
Yeah. So this is similar kind of thing about why the Sun is so bright. Because the same mechanism that produces all the light, that nuclear fusion reaction that we were talking about, it produces all the warmth as well. And so it’s all just forms of energy. So that same fusion reaction where they’re fusing two hydrogen into a helium and releasing a tremendous amount of energy. A good portion of that energy we observe as heat or we feel as heat. And so it’s all part of the same sort of a spectrum of light where we have the infrared light, which is what we observe as heat. We had the visible light, which is what we see. And then we have the X Ray light, which is what we use to study the Sun, or ultraviolet and X Ray light. And all of those different wavelengths of light are all on the same spectrum. And they’re all coming from the Sun all the time. And so, depending on how we look at the Sun, we either see it as warmth or as bright or as you know, x-ray ultraviolet light, which gives us sunburns, but also use helps us to understand how the Sun works itself.
Victoria:
(Johann – Why does the Sun appear red/bright orange at sunrise, but not red/orange later in the day?)
Cool. This next question is from Johann. Why does the Sun appear red/bright orange at sunrise, but not red/orange later in the day?
Dr. Kirk:
Ooh. That is a good observation, man. That is, yeah, somebody has been thinking about that for a while. So the Sun, it’s a little misleading because it’s not the Sun that’s changing, it’s our atmosphere that’s changing. So it’s the Earth atmosphere that’s causing the difference.
Okay. So if you think about it, when the Sun is at, let’s say noon, or like directly above you, there’s a certain layer of air and dust and water vapor and everything that makes up the Earth’s atmosphere that’s above you. It’s, you know, a little bit thick, but, you know, I forget how many kilometers, a hundred kilometers thick, don’t quote me on that number, but that’s about a hundred kilometers thick and so that thickness of air is a hundred kilometers thick at noon.
When it’s at sunset, all of a sudden, that sunlight passing through a whole lot more air to get to your eye, because it’s now added what we call an oblique angle, which means it’s at a very low to the horizon. It’s passing through all the air between you and the edge of the Earth. And so that path, that light travels, is hitting all so much more air and dust and water vapor and all those other things. And what that’s doing, all that dust and water vapor, is scattering out all the blue light. So all the light that’s blue in the Sun is leaving, is getting scattered away. And so what we see is red, it’s the only stuff that’s left.
And so it’s not actually in the Sun is not any different color itself. It’s the filter that we’re seeing that Sun three, which is our Earth’s atmosphere that’s changing how we see the Sun and how it appears to us.
Victoria:
Okay, that makes sense. So, if someone were to hypothetically be sitting on top of the atmosphere, it would all look the same, right?
Dr. Kirk:
Yeah, exactly. So if you’re in the international space station or you’re an astronaut, the Sun is always this bright white color, because it’s the combination of all the colors of light combined together you get white light. And so the Sun always looks bright white. It doesn’t actually change whether it’s morning time, noontime, or evening time.
Victoria:
(Emilie – Why does it sometimes not get dark until really late and other times it gets dark after school?)
Awesome. Emily wants to know, another viewing the Sun sort of question, why does it sometimes not get dark until really late and other times it gets dark after school?
Dr. Kirk:
Yeah. Well, it depends on where you live on the Earth. Cause I can tell that you either live in the Northern hemisphere or the Southern hemisphere and not on the Equator. How do I know that? Well it’s because the Equator, the light is almost always consistent in terms of when the Sun rises and sets. It changes a little bit, but almost always.
So what’s going on there is actually the orbit of the Earth. So what’s happening is the Earth, as it goes around the Sun in one orbit. So as the Earth goes around the Sun once, that’s one year. During that time, as it goes around the Sun, the Earth has tipped either the Northern hemisphere towards the Sun, the Northern half of the Earth towards the Sun, or the Southern hemisphere, the Southern half of the Earth tips towards the Sun. So as it goes around in the Northern summertime, the Northern hemisphere is tipped towards the Sun a little bit more. And then the winter time, the Northern hemisphere tipped away from the Sun, and the Southern hemisphere is tipped towards the Sun.
Okay. So what does that mean for people on the ground? So let’s say you’re at 45 degrees longitude North. Okay. So that would be like Oregon from where I grew up was 45 degrees North or Minnesota or Maine, those are all places on the globe that are 45 degrees North. What that means is that in the summertime you get much, much longer days and shorter nights. And the winter times you get much, much longer nights and shorter days.
This even goes to an extreme in once you get above that Arctic circle. So above the Arctic circle, you can have days that last 24 hours, the Sun never sets; and nights that last 24 hours, the Sun never rises. So if you’re in Northern Alaska, let’s say, in the far, far Northern shore of Alaska, right on the Arctic ocean. The Sun will never set for you for right around the summer solstice right around mid-June. And then the opposite in the winter. Okay.
So now let’s say the opposite extreme. Let’s say you’re sitting on the equator, you know, you’re in Ecuador, I know Ecuador cause its equator, Ecuador. Yeah. That’s how I remember it. Anyway, so you’re sitting right on the equator. Okay. So you’re sitting right on the equator, that when the Northern hemisphere tips towards the Sun, things change for you a little bit. But then when the Southern hemisphere towards the Sun, they changed a little bit back the other way. So your day nights will change just a little bit, not very much by a few hours versus in the, you know, all the way up at the Arctic circle. It can change by as much as 24 hours.
So. A little bit more directly. The reason it gets light earlier in some parts of the year and gets light later in other parts of the year is because of the Earth’s orbit and the way the Earth has tipped towards the Sun.
Victoria:
(Janelle – What’s it like to work for NASA?)
Awesome. That’s a good explanation. That makes a lot of sense.
Okay. Switching gears a little bit, Janelle wants to know what’s it like to work for NASA?
Dr. Kirk:
Oh, that’s a good question. So I’ve been working for NASA on and off since 2007. So I had finished my college degree and got a job after a short break. I got a job working as a system engineer. So that was my first exposure working at NASA. So the first day you show up at NASA, it’s like amazing. You’re star struck. This is NASA. They landed people on the Moon. I mean, these are the best and brightest from around the world that come and work at NASA and it is super exciting.
And then after about two weeks, it becomes like every other job where you go in and sit at your desk and you work at your computer and you talk on the phone and you have meetings and you know, all of these other things.
But what thing that stays the same, that’s just, I just can’t get over, is that when you hear about a new satellite being launched or a new Rover going on to Mars, oftentimes it’s NASA that has a role in that, and then we’re actually building it. And so if I want to go over and look at the next satellite that’s going to be launched. I get up from my desk and it’s about a 10-minute walk from where my office is. But I can go and look through a window and see the next satellite that’s being launched. And that is just, it’s incredible because gives you an idea that, you know, it’s not just my work. That’s important. Everybody’s working at NASA that’s really including people from around the world that are coming together to advance that knowledge of science just a little bit further. So these are thousands and thousands of people all coming together for a common goal. And it’s sometimes it’s easy to forget that when you’re sitting on phone calls, taking meetings, writing emails on a computer, working on computer code which is what I do a lot. But, that sense of just exploring what’s unknown is still really palpable at NASA. Really. You can really feel it. And that’s pretty exciting.
So if you ever get a chance to visit one of the NASA centers, whether it’s Goddard, where I work, or whether it’s down in Florida or Houston or out in California, definitely take the opportunity to go. It’s worth just even for a quick tour to see what everything is going on there.
Victoria:
(Talya – How does the sun affect the Earth?)
That’s awesome. Back to some Sun questions. Talya wants to know how does the Sun affect the Earth?
Dr. Kirk:
Oh, my gosh, Talya, you asked a big question. That is a huge question. In fact, I would argue that is the sole reason that my job exists is because the Sun affects here.
So let me tell you a quick story. And it won’t give you all the reasons the Sun effects here, but it’ll give you a little bit of an idea. Okay. So back in 1859, there was a scientist and astronomer named Richard Carrington. He had a solar telescope, so it’s one of these telescopes with a filter on it. He was looking at the Sun and mapping out spots on the Sun, sunspots, and making drawings of them, recording them about where it was and how long they were lasting. And this sunspot group, this cluster of spots in the Sun, was really big and it was sort of bizarre looking. So he’s making careful measurements of that. And he saw a white flash, this flash of light coming out of these spots. I was like, Oh my gosh, that’s crazy. He, you know, wrote it down, made a note e to make sure that he confirmed it with other people, there are scientists,
“Did you see this white flash that came out of these spots?” Well about 24 48 hours later, a day between a one and two days later, all these strange things started happening on Earth.
First of all, there were Northern lights that started appearing. So like, the Northern Southern lights, if you haven’t seen them, they only happen at Northern latitude. There are these green curtains of light that kind of hang in the sky who were really crazy looking stuff. They were happening all the way down to the Caribbean. So you could see Northern lights all the way down to the Caribbean throughout the entire US.
The other crazy thing that was happening is, this was a time when they were using telegraphs, so these are long wires that between two receivers and they send messages back and forth to each other along these long wires. Well, all of these wires starting getting electric charged built up into them so much so that they’re sparking and starting fires in their telegraph huts all across the United States and all across the world.
And that was the first hint what had happened on the Sun was actually connected with what was going on here at Earth. So through a lot of research and years later, it was Richard Carrington and that generation of scientists that started to piece together that what the Sun was doing was actually impacting the magnetic fields of the Earth, and that’s really how the Sun and the Earth interact. The big way is that the Sun has these magnetic fields which is out in interruptions. It’s called coronal mass ejections, or solar flares. That’s what Richard Carrington saw was a solar flare. And it bursts out these magnetic fields and the magnetic fields travel through space and hit the Earth’s magnetic fields. So that’s the same magnetic fields that cause your compass needles to move if you have a compass, that’s the Earth’s magnetic field, same magnetic fields that hold your magnet, refrigerator magnet to your refrigerator, so was magnetic fields. The Earth has a big magnetic field. The Sun bursts out magnetic fields as well. And when they interact with together, we get these amazing processes. One of which is the Northern lights, right. Another, which is that you can actually get electricity generated in the ground itself. And that was what was causing the electricity in the telegraph wires.
So all of these effects are cumulatively called space weather. And that’s how the Sun affects the Earth. And this an entire field of study. There are so many complex things about how it affects GPS receivers. So any sort of like GPS receivers you have on your phone, any sort of space communications. If you have a TV signal coming from a satellite, that will be affected by space weather by what the Sun is doing. Any sort of satellites in orbit, those are affected by space weather. Astronauts, those are affected by space weather. So all of these things are impacts of the Sun on our Earth. And there is, I don’t know, probably 5,000 people around the world are studying space weather to this day.
Victoria:
(Stasia – What are polar coronal holes?)
That is so cool.
Okay. A good follow-up to that. This is a question from Stasia. What are polar coronal holes?
Dr. Kirk:
Well, you now you’re talking my language, right? So polar coronal holes are a thing that I started studying when I was about 22 years old. I’m a little older than that now. And so polar coronal holes are these darks spots, these dark patches on the Sun, specifically at the poles, that’s why they’re called polar. So on the North and South pole of the Sun, there are these dark patches in the x-ray and ultraviolet light of the Sun. It’s just like it’s missing. Yeah, it’s just dark. So yeah, the question is why, what’s going on there?
Well, the reason that that those patches are dark is because of those magnetic fields I was just talking to you about. These magnetic fields are what we call open, and when I say open magnetic fields, that’s a bit of a jargon term because what that means is that instead of making little loops that connect back down to the Sun, they extend off into space, just kind of without hitting anything, they just kind of drift off into space. And what happens when you have a magnetic field that’s set up like that is that it allows materials from the Sun just flow off into space uninhibited, and nothing stopping it, just allows it to drift off in space, which causes the Sun to look dark when we’re observing.
So that’s what polar coronal holes are. They’re the indication of these magnetic field structures that are these big fields that lift off the Sun and then just extend off into space into interplanetary space stretched throughout the entire solar system. But they all start right at the pole, North pole and South pole of the Sun.
Victoria:
(Max – How does the solar cycle work?)
Wow. Alright. Max wants to know how does the solar cycle work?
Dr. Kirk:
Holy cow, Max, this is that’s an amazing question. Okay. Then I’m going to say right now as that we don’t actually know. Okay. That means that we don’t have a hint. We don’t know what’s going on at all, but ultimately that’s an unsolved question. That is something maybe for you to figure out and your career is studying the Sun.
Let me explain what the solar cycle is for people who might not know. So the Sun goes through periods of activity and quiet. And when I say solar activity, I mean, there are lots of flares and lots of sunspots and lots of eruptions on the Sun. And then quiet is when there aren’t as many, there might be one or two. They’re just the Sun’s pretty well behaved. That period where it goes from quiet to active and to quiet again, a solar cycle typically lasts about 11 years. And we know this because we’ve been observing how many sunspots are on the sun since the mid 1700, scientists have been looking at the Sun very carefully and recording the number of sunspots that are on the Sun. And so we can track this 11 year cycle over and over and over again. And so that’s a solar cycle. Okay.
So how does it work? Well, the simple answer is magnetic fields. It all comes back down to magnetic fields. The Sun is driven by these magnetic fields. So the Sun generates magnetic fields in its core in its interior. And then those magnetic fields work their way up to the surface and cause solar eruptions, solar flares, sunspots, coronal holes, all these features that we observe on the surface.
Why does a solar cycle vary by 11 years? Why is it 11 years? What causes it to vary exactly? Those are still all open questions. We were looking in the inside of the Sun trying to understand those today.
Victoria:
So lots of things that Max can answer when he gets older.
Dr. Kirk:
I hope so. I hope you’ll tell me the answer cause I’d love to know.
Victoria:
(Charlie – What is the craziest thing you have seen or found studying the Sun?)
Charlie wants to know what is the craziest thing you have seen or found studying the Sun?
Dr. Kirk:
Hmm, the craziest thing. Okay. I’m going to take crazy sort of liberally. I am going to say what the coolest thing is. Okay. So the coolest thing I’ve ever seen studying the Sun was seeing a total solar eclipse, by far the coolest thing I’ve ever seen. If you had never seen one, there they happen every couple of years over land. Go travel and find one. There’s one coming up. That’s gonna across the United States in 2024. It’s going to come up through Texas, and then sweep up towards Canada, kind of northeasterly. It’s worth a trip. It is. I promise you however much pain you have to go through. That’s worth it. Okay.
So what you see is in a solar eclipse, the Moon covers up the Sun. So the Moon completely covers up the Sun and makes it dark on the ground. But what you can see then is the outer atmosphere of the Sun when the Sun is being covered up by the Moon, and that outer atmosphere of the Sun is called the Corona. It’s coronal holes, that’s the same section of the atmosphere. So the Corona of the Sun are these crazy wispy structures that are so delicate and they’re so fine. And they’re all caused by these magnetic fields I’ve been studying. So it was the first time back in 2017 that I got to see with my own eyes what I’ve been studying for more than a decade. That’s amazing. That is the absolute, most amazing thing I would call it the craziest thing I’ve ever seen was the thing that I’ve been studying in books and on paper and onto my computer, I got to see it with my own eyes. That was pretty awesome.
Victoria:
That’s amazing. That must have been so surreal when you actually saw it.
Dr. Kirk:
Oh, it was, I mean, it was overwhelming. Cause you know, whether I like it or not, I’ve kind of devoted most of my life to studying this thing. And so, to be able to actually observe it, and it’s not just a picture, you like, I can actually see it with your own eyes. That’s one of the few times when you can look at the Sun without any filters. is during a total solar eclipse. And so that was just absolutely unreal. And that’s why I would recommend it to everybody. Everybody should go see one, at least once in their life, you have to go see one.
Victoria:
Yeah. Mark your calendars for 2024.
Dr. Kirk:
Yeah. 2024. Yep.
Victoria:
I still have the little like paper glasses to wear, I have mine in my drawer waiting for 2024.
Dr. Kirk:
So a little PSA. Don’t use the glasses you used in 2017 in 2024. They have an expiration date. So they’re only guaranteed to filter the appropriate amount of light for I think it’s a couple of years most of them. Some of the glass ones will actually last longer, but then they have the paper ones after a couple of years, you should really throw them away because the filters can get nicked or damaged. And then they’re just unsafe. So. Yeah. Don’t worry about throwing them away. There’ll be plenty more classes coming out, and it’s better to be safe than take any chances.
Victoria:
Good to know. Thank you.
Dr. Kirk:
Of course.
Victoria:
(Max – How big can a star get, and how long do they live?)
All right. Let’s get into some questions about stars. Max wants to know how big can a star get, and how long do they live?
Dr. Kirk:
Okay. So stars can get incredibly big, bigger than you can imagine. I promise you. You can’t imagine that big. Imagine the biggest thing you can imagine, and the stars can get bigger than that. Okay. Bigger than the entire size of the solar system. They can get, you know, of thousands of times bigger than our own Sun. The stars are bigger than our own Sun. And incredibly bright too, many hundred times the brightness of our own Sun. So these stars you can see in the sky, some of the bright stars in our sky are really huge, like Vega, Betelgeuse is also a really big star.
But as stars go through their life’s cycle, I would say are born, they burn through their fuel, and eventually they burn now. They actually changed size. And so our Sun, as it gets older, will grow a bit and actually get grow to about the orbit of Mars. And so stars actually don’t stay the same size their entire life. They actually can grow as they go through their life cycle and as they start to burn up all their fuel.
Oh, how long do they live? I guess that was the other part of the question. Okay. So depending on the type of star, you get a different lifetime. So the biggest stars actually live the shortest. It’s kind of an opposite way you would expect. But what happens is to have all of that matter, all of that hydrogen and helium, stuck into a star in order to make it that big. It also makes it really hot and just starts making it burn through its fuel a lot faster. And so the biggest stars will live a couple of hundred million years. And those are the absolute biggest stars, a couple of hundred million.
Yeah. The smallest stars on the other hand, they’re very efficient using their fuel. They’ll just kind of sip on it for billions of years. And our current estimate, again, this is an estimate because we haven’t actually seen anything that has gone through its entire life cycle, is about 20 billion years for a star, that’s older than the entire age of the universe. So the smallest stars can live more than the lifetime of the entire universe and still be burning.
Our Sun is kind of a, I don’t know, it’s a medium, small star. And so our Sun is about four and a half billion years old, and it’ll live for about another four and a half billion years. And so it’ll be about eight or 9 billion years by the time burns out.
Victoria:
(Anabelle – People say the Sun is going to explode someday. Do you know when that is? What is it going to be like when the Sun explodes?)
Wow. And that sort of answers Anabelle’s question. Anabelle says, people say the Sun is going to explode someday. Do you know when that is? What is it going to be like when the Sun explodes?
Dr. Kirk:
Yeah. So the Sun is not going to explode like you’d hope it would. It’s really not going to be that amazing. I mean, it’s going to be amazing, but we’re not going to be here to observe it. But the Sun’s going to more like it’s going to belch. It’s not going to explode. It’s kind of just sort of burn off its outer atmosphere.
You have to have a star that’s a lot bigger than the Sun to actually explode to get a supernova. So if you take the Sun, let’s say if you take about a two and a half, maybe three times the Sun as three Suns and stick them all together, that’s about how big you need in order to actually get a supernova. And so what a supernova is, is that the sun burns through its fuel. The outer atmosphere starts to collapse in on itself. As a collapsing on itself, everything gets squeezed really tight. As soon as it gets squeezed really tight, a lot of energy is produced for through the nuclear fusion and it explodes and bursts itself apart.
The Sun, what will happen is the outer atmosphere will kind of contract. And as it burns through its fuel, the outer atmosphere will contract down and it will get smaller and smaller and smaller. And then it’ll just sort of bounce off the inside. And it’s kind of belch off into space and it’s going to form a planetary Nebula.
So the Sun right before it explodes, it will be about the size of the orbit of Mars right now. So the Earth will be long gone. It’ll already be sucked into the Sun. It’ll be this kind of loose outer atmosphere of the Sun. And then it’s going to the atmosphere will in a short amount of time, we’re talking about years, in talking about the stars short amount of time is years, what will happen is this atmosphere will collapse in on itself and then burst out into this cloud, it’s called a planetary Nebula and that’s where new stars new planets are formed.
Victoria:
(Gage – How many stars are like our Sun?)
Cool. Alright. this next question is from Gage. How many stars are like our Sun?
Dr. Kirk:
That’s a really good question. Up until fairly recently, I want to say up until the last 10 years, we really had no idea. We really didn’t know how many stars were similar to ours. And we were kind of unsure of how many had planets and how many had solar systems and all of that.
NASA launched a mission called Kepler about, I think it’s about 10 or 15 years ago now. Yeah, about 15 years ago now. And Kepler went up and studied stars, did a really close study of stars in a very small patch of the sky. What Kepler discovered is that there are a lot of stars that are similar to ours, but not exactly the same.
So we live near a funny star. We’re not really sure why it’s that way, but it doesn’t behave like most of the other stars that are the same age and the same composition and the same weight and the same size and all of that. Our Sun doesn’t exactly behave the same. It’s actually too quiet. It doesn’t have enough solar flares and enough sunspots and enough explosions. It’s actually pretty quiet and pretty tame. And so we’ve seen a few other stars that are similar, but this just a handful. I mean, like I want to say, you know, less than 10 that are really very similar or like analogs to our Sun, mostly other stars that we observed that are same size and the same weight and all that, there are much more active. If there are a planet around there, that might have life, it will have long sense, you know, blasted that planet with radiation and killed all the life. And so there’s just an unstable.
So the question is still open. Why is our Sun weird? Do we not understand how stars work that our Sun isn’t weird, but right now with the best data we have looks like our Sun’s such a strange one. It’s pretty different than most of the other stars.
Victoria:
Wow. That’s weird.
Dr. Kirk:
Yeah. There’s a lot of good questions out there that we still don’t know the answer to.
Victoria:
Yeah. So Gage, you can answer that question.
Dr. Kirk:
Yeah. Again, please look me up. Let me know. I want to know why.
Victoria:
(Theo – Do you have a special telescope that lets you look at the sun?)
Yeah. Okay. Let’s see, you’ve touched on this a little bit before with the filter in the telescope. But Theo wants to know, do you have a special telescope that lets you look at the Sun?
Dr. Kirk:
Me personally, I don’t have a special telescope. I’ve used them. I’ve borrowed them from friends or from my place of work. Goddard has a few solar telescopes lurking around, but I personally don’t have one.
You can buy them though, if you want. They’re a little expensive. There are a few $100 for a small one. If you want a nice one, you’re talking a couple thousand dollars. So they’re not cheap, but you can definitely buy them if you’re interested.
Victoria:
(Kayla – What would happen If an asteroid hit the Sun?)
Cool. Okay. This is an interesting question from Kayla. What would happen if an asteroid hit the Sun?
Dr. Kirk:
I like the way you think, Kayla. That happens all the time. It really does. Asteroids hit the Sun all the time. So they’re not exactly asteroids. We don’t call them asteroids because asteroids mean that they come from the asteroid belt, they’re little shards of planets that live near the asteroid belt.
But we do see comets. So these comets are similar type of makeup. They’re chunks of rock and ice, but they come from much farther out in the solar system and they come on these crazy orbits into the solar system. And you may have heard of Haley’s comet. That’s a famous comet. There was just a comet the other day that we could see it right at dusk. I forget the name of that, but anyway, there’s a comet that we could see its tail.
Those comets, which are similar in how they’re made up from asteroids. They hit the Sun all the time. They actually come in and there’s some great pictures of it, an asteroid coming in behind the Sun and then just disappearing. So if an asteroid hit the Sun, it’s going to get vaporized, the sun’s way, way, way too hot. All that ice and dust that that’s makes up these asteroids or these comets and asteroids. There’s just no chance, the Sun’s going to win every time. It’s just going to completely vaporize it. Sun won’t even flinch and won’t even feel a thing. But it’s really cool because we can actually watch these things come into the Sun. They’re called Sun-Grazing Comet. You can see videos online. If you go onto YouTube and type in Sun-Grazing Comet, you can see photos of these things coming in and hitting the Sun.
Victoria:
Cool. I’ll put a link to one of those YouTube videos in the description of the episode, so students can click on it and check it out.
Dr. Kirk:
Of course, yeah.
Victoria:
(Linzi – Are there volcanoes on the Sun?)
Okay. This is our last science question. And then we get into some questions about you. Linzi wants to know, are there volcanoes on the Sun?
Dr. Kirk:
That’s a good question. So volcanoes on Earth are made up of molten rock. You know, the magma coming up from the interior of the Earth and gas and water vapor and all these other things. There isn’t molten rock on the Sun, cause the Sun is too hot to have molten rock. Everything is a gas. In fact, it’s a plasma. It’s so hot. It’s not even a gas anymore. It’s just this big soup of material called plasma.
So there aren’t volcanoes like that. However, there are eruptions on the Sun, like solar flares. And there are these points on the Sun, sunspots, where all these magnetic fields get concentrated and pushed out through the surface of the Sun, same sort of processes that exist on the Earth to move material out from the interior of the Earth exist on the Sun as well.
Victoria:
(Sheamus – Why did you decide to become a scientist?)
Switching gears a little bit. We’re going to get into some questions about you. Sheamus wants to know why did you decide to become a scientist?
Dr. Kirk:
Ooh, that’s a good question, Sheamus. I think I always was a scientist. I think science chose me, rather than me choosing science. The reason I say that is because always wanted to know why. I, you know, in school a teacher would explain something and I wouldn’t quite make sense because they didn’t explain it all the way. I wanted to know more. I want to know why. I always wondered about the stars and wanting to know more about the planets. I’ve always wanted to know like the questions of like, why is the sky blue? Why is the grass green? Why can we see through some things and not see through other things? I mean, all of those questions that you experience all the time, those just always stuck with me. And I wasn’t satisfied until I knew the answer. And so science was just natural for me because that science is the profession of asking why of not resting until you know an answer. And so I think I became a scientist probably shortly after I was born. At least I think my parents would tell you that. But I’ve always loved the idea of asking questions and being curious and continuing to do research until you figure out why something is true.
Victoria:
(Sheamus – What is the best part of your career and why?)
All right. A follow-up from Sheamus. What is the best part of your career and why?
Dr. Kirk:
Ooh, that’s another good question, Sheamus. So the best part of my career, I would have to say is traveling around the world and talking to people. Cause there are some really fun people, interesting people, smart people that exist all over this country and this planet. And one really cool part of my job is being able to travel to those places, whether it’s to an observatory and just do make studies of the Sun, or whether it’s to a conference to talk with other scientists, or whether it’s to classrooms and to talk to students. And I can do that as part of my job, and it’s so much fun.
So for example, I went to Katmandu in Nepal for a couple of weeks and taught students there. I had been to, let’s see here, I think every continent except Africa for conferences or workshops. I got to go to Belgium to work at an observatory there just because they said, okay, sure, come on over. You know, it was it was a crazy thing. And so this idea of talking with people and working with people has been not only something I’ve enjoyed, but it’s really something that’s given me a lot of enthusiasm to keep on going, because there’s always a new person you’re going to meet on the other side of the planet that you have a lot of in common with, and you make friends and then you stay friends for a long time and start working together.
Victoria:
(Leigh – What are you most proud of?)
That’s awesome. This next question is from Leigh. What are you most proud of? And I think this can be professionally or personally.
Dr. Kirk:
What am I most proud of? Wow. That’s a big question. So I think the thing that I’m most proud of is being able to inspire other people to be curious. And that’s not just students, that’s everybody. That’s people I sit next to on the airplane when I could fly to places, haven’t been flying recently. Or that’s you, that I’m talking to you on this podcast. I get really excited when people come back to me and say you inspired me to go off and ask more questions and do more research. And that has always been a driver of mine. And it had been something that I’ve gotten excited about, not only to talk with people, but to hear what they did next and the fact that I had a role in that. And so, that I would say is my most proud feeling.
But that expands beyond just students. You know, if I go to a workshop and I talk to other scientists, and other scientists say that was an amazing idea and it spawned this whole other line of thinking for me, I changed the way I thought. Those are the moments I’m most proud of is when I can help people think in a different way. That’s what’s really exciting.
Victoria:
(Riley – Were you interested in the Sun as a child?)
That’s a really amazing answer. Okay. Riley wants to know, were you interested in the Sun as a child?
Dr. Kirk:
Oh, this is an easy question. No. I wasn’t interested in the Sun when I, you know, up until like a few years ago, I mean. I thought I wanted to study the cosmos, study galaxies, study black holes, you know, neutron stars explosion. I love space. I fill up space when I was a kid. I mean, I’ve always loved stars and planets and, you know, black holes and all that cool stuff, galaxies. But no, I thought the Sun was boring.
I thought the Sun was boring up until I was probably, I don’t know, 22 and I got my first job at NASA and I still thought the Sun was boring, but they were going to pay me money. So why not? It was NASA. They’re going to pay me money, who cares what I was doing. And it was at that point that I started to get interested in the Sun.
However, it wasn’t until I started my master’s degree in PhD. So after I finished that first round of working at NASA, that I actually started enjoying looking at the Sun. It was all just sort of like, well, this is interesting. I can do this. I’m not bad at this, but I’m not particularly interested in it. But it wasn’t until much later that I actually got interested in it, got really excited. Now I really love it. So you can’t take it away from me.
Victoria:
(Rex – Do you drink a lot of coffee?)
(Daniel – What’s your favorite home-roasted coffee? And how old do you have to be to drink coffee? I’m not allowed to.)
Couple of questions about your hobbies. Rex wants to know do you drink a lot of coffee? And Daniel wants to know what’s your favorite home-roasted coffee? And how old do you have to be to drink coffee? I’m not allowed to.
Dr. Kirk:
Oh yeah. Okay. Well, so again, coffee was one of those things that I didn’t like for a long time either. Yeah, I just didn’t like it, it wasn’t for me. I probably drink more coffee than the average person, but I wouldn’t say a ton, you know, I just like really good coffee. I’m a bit of a snob that way. I really like good coffee. So I got into home roasting coffee mostly because really good coffee is expensive. And if you roast it yourself, it’s a lot cheaper. So I got in it to save money.
But then it became a little bit of a hobby and a little bit of an art. Now it’s not just a science of how much do you roast it to what temperature, but it’s a little bit of an art like this being how do you roast it in order to get the best flavor out of it?
So my favorite home roasted coffee, I just roast some Guatemalan coffee. That’s fantastic. I started off roasting Ethiopian coffee. That was the first coffee that I was roasting and that I took to a really dark roast, really dark and toasty. Now I’m kind of into light roasts, which are a little bit more fruity taste flavor.
But in general, you have to be a bit older to enjoy those flavors. And the reason why I say that is because coffee is bitter. It’s just really bitter. And until you can enjoy that bitter flavor, which happens, I don’t know, probably when you’re 20, 25, you start enjoying bitter flavors. Then that’s when you start enjoying coffee. So when you’re small, you know, you like sweet things, you like salty things, you like sour things maybe, but bitter is generally a flavor that people don’t like. And then as you get older, your tastes change a little bit and you start liking bitter things. And for me that was coffee.
Victoria:
Awesome. One of my friends sent me this like really good coffee from Puerto Rico. And that’s what I’ve been drinking mostly. It’s so good.
Dr. Kirk:
I know it. It kind of changes you when you find a good coffee and you’re like, I didn’t realize it could be this good. And then you get spoiled and you’re like, I want it this good all the time.
Victoria:
(Sophie – Where do you like to go on vacation?)
Yeah. Okay. Speaking of other things you do outside of work, Sophie wants to know where do you like to go on vacation?
Dr. Kirk:
Hmm, that’s a good question, Sophie. So I grew up in Oregon near the mountains and near the ocean. And now I live in Washington, DC, which is near the ocean, but not near mountains. So I really miss the mountains. That’s where I like to go on vacation. I love to go up to the mountains and whether that’s during the summertime and going on hikes, or in the winter time and going skiing or snowshoeing. I love being in that Alpine environments where it’s cold at night and maybe a little warm in the day, but yeah, I certainly missed that and that’s where I code these days.
Victoria:
(Ann – If you could go anywhere in time and space where would you go?)
Nice. And this is our last question from Ann. If you could go anywhere in time and space, where would you go?
Dr. Kirk:
Oh, no, anywhere in time. Ugh. Ugh. Do I have to pick one? Oh boy, this is hard.
Victoria:
You can have a couple options.
Dr. Kirk:
Okay. So, one place in time and space that I would like to go, even though I said it was boring when the Sun exploded, I still would want to see it. I still would want to be able to be in that spaceship in my space suit with my special filter sunglasses on and watch the Sun explode. That would be spectacular. Oh, terrifying. That’s spectacular. As long as I could go back afterwards. Cause after the Sun explodes, it’s going to be really dark and cold and I don’t want to be around afterwards.
But in general, I have a long wondered what the Earth looked like before humans evolved to be what we are today. I want to see what the Earth was like before that. And so where I would go, it could go anywhere in time and space would be like, maybe right here, in like right where I’m sitting, but go back a hundred thousand years. Maybe 200,000 years and not too far back, not, you know, not maybe dinosaur, it’s not that far back. But just like standing right here, what would it look like before humans ever had cities and built up civilization? What did it look like right here? So I think that’s where the other place I would go in time and space.
Victoria:
Those are both great answers. Okay. Well that is all of our questions, but do you have any questions of your own for the listeners?
Dr. Kirk:
Absolutely. So I have a little bit of a homework for all of you. I’m not going to check up. So if you don’t do it, I’m not going to know. But what I want you to do is for an entire month, I want you to go outside and find the Moon. You can go outside the same time every time, like, I don’t know, let’s say five o’clock every day 5:00 PM or, you know, 8:00 AM. It doesn’t really matter. I want you to go outside every day for a month and find the Moon. A lot of times, you’re not going to find it, but what you are going to find is that the Moon evolves in a way that you’re probably not expecting: it’s up during the daytime, it changes the size, the shadows move across the Moon, the phase of Moon.
So the phase of the Moon are caused by sunlight, and how sunlight hits the Moon. But what you can do is if you look at this phase of the Moon, you can start getting a sense for our place here on Earth and as it relates to our solar system. And so that’s the first step in kind of starting to look outward.
So that’s my homework question. And my homework problem for you is to go outside and find the Moon every day for a month.
Victoria:
Awesome. I think I’ll do that homework along with listeners. All right. Well, thank you so much for joining us. I learned a ton, and I’m sure the listeners did too.
Dr. Kirk:
Yeah, well, I’m happy to be here and talk with you guys. It was an absolute pleasure of mine. If you want to see more pictures of the Sun, like the ones I was talking about, the website is helioviewer.org (https://www.helioviewer.org/), and we’ll put that in the notes. You can see NASA’s images of the Sun in nearly live, it’s delayed a little bit, but you can see the same images that I used to study the Sun. You can look at them too.
Victoria:
Cool.
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