Planetary Radio • Jan 12, 2022

We have touched the Sun: The Parker Solar Probe’s triumph

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Nicola Fox

Associate Administrator for NASA’s Exploration Systems Development Mission Directorate for NASA

Nour raouafi

Nour Rawafi

Parker Solar Probe Project Scientist and Principal Professional Staff at the Johns Hopkins University Applied Physics Lab

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

The Parker Solar Probe dipped within the corona on its eighth encounter with our star. It found phenomena that have surprised and delighted heliophysicists, and it captured a movie that is one of the greatest space videos ever. We’ll talk about these and more with Nicola “Nicky” Fox, director of NASA’s Heliophysics Division, and Nour Raouafi, the mission’s project scientist. Get out your calculators! Winning the new space trivia contest will require some basic arithmetic.

Touching the Sun
Touching the Sun NASA's Parker Solar Probe became the first spacecraft to fly through the Sun's corona in 2021. These images show coronal streamers, bright features moving upward in the upper images and angled downward in the lower row. Previously, streamers have only been seen from afar.Image: NASA/Johns Hopkins APL/Naval Research Laboratory

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Watch the Closest Footage of the Sun’s Atmosphere Ever Bill Nye comments over real footage from inside the Sun's corona from the Parker Solar Probe.

Parker Solar Probe approaches the Sun
Parker Solar Probe approaches the Sun Artist’s impression of Parker Solar Probe approaching the Alfvén critical surface, which marks the end of the solar atmosphere and the beginning of the solar wind. Parker Solar Probe’s crossing into this zone in April 2021 means the spacecraft has touched the Sun for the first time.Image: NASA/Johns Hopkins APL/Ben Smith

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Trivia Contest

This Week’s Question:

What is the sum of the number of hexagons of one Keck 10-meter telescope primary mirror divided by the number of JWST hexagons plus the Palomar Hale telescope primary mirror diameter divided by the Mount Wilson Hooker telescope diameter? Use standard mathematical order of operations.

This Week’s Prize:

A beautiful Startorialist JWST black-on-gold necktie.

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, January 19 at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

In the spectrum of the Sun’s light, who are the main solar absorption lines (basically, for visible light) named after?


The winner will be revealed next week.

Question from the Dec. 29, 2021 space trivia contest:

How many deep space launches were there in all of 2021? (Launches, not spacecraft!)


Three deep space launches (Moon and beyond) happened in all of 2021: Lucy, DART and the JWST.


Mat Kaplan: We have touched the sun this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. The Parker Solar Probe, named for 94-year-old pioneering solar researcher, Eugene Parker, has gone where Parker probably never imagined a machine built by humans would ever go. On its eighth close encounter with our star, the spacecraft dipped within the sun's corona. What it found there is dazzling in every sense of the word. We'll talk about it with the director of NASA's Heliophysics Division, Nicola Fox, and the mission's project scientist, Nour Raouafi. Then we'll hear how that star we race around is making it difficult to see our neighboring planets at the moment. Never fear, Planetary Society chief scientist, Bruce Betts, has much more to entertain us, including a new space trivia contest with a great prize.

Mat Kaplan: I've got a favor to ask. It has been years since we asked you to let us know how you feel about Planetary Radio in a survey. Here's your chance. I hope a lot of you will go to and answer a few easy questions about this show. There's no obligation. We won't bother you with other mail and we're not asking you to become a member, though we wouldn't mind if you did, of course, but I'll be very grateful if you help us out with this. Again, Thanks.

Mat Kaplan: JWST. Wow. It happened. Here's the almost anticlimactic moment when on Saturday, January 8th, we learned that the new space telescope was fully deployed.

Speaker 2: This is [inaudible 00:01:56] we have reached the end of deployment and we are pre-loading into the latch patch.

Speaker 3: All right. [inaudible 00:02:03].

Speaker 4: You see people clapping? Yes. Wonderful.

Speaker 3: Everyone [inaudible 00:02:09] and clapping.

Mat Kaplan: Now begins up to five months of fine tuning, including the careful ultra precise alignment of those 18 gold-plated mirrors. Like the telescope itself, our coverage of the JWST is just getting started. The Planetary Society congratulates NASA, and the entire team behind this great new observatory. The January 7th edition of the Downlink, our free weekly newsletter, covers the Biden administration's decision to keep the International Space Station operating through 2030. This is something I talked with Casey Dreier and Brendan Curry about on our monthly space policy edition of Planetary Radio. The guys and I also mentioned the meteor that exploded over Pittsburgh on New Year's day. And you'll find that story in the Downlink as well.

Mat Kaplan: The image that made me do a double take was the comparison of Jupiter's squiggly surface with a phytoplankton bloom in the Baltic Sea. I hope my colleagues didn't mix them up. They are uncannily similar. Nature loves to repeat itself. See for yourself at Imagine spending your long life learning and speculating about how stars work and then having a space mission named for you actually visit one. As you'll hear, Eugene Parker is as thrilled by what is being learned as any scientist on the Parker Solar Probe mission or any of the rest of us for that matter. Nicola or Nicky Fox, and Nour Raouafi are no less enthusiastic, as I learned when I talked with them via Zoom a few days ago. Nicola, Nicky, and Nour, thank you so much for joining us on Planetary Radio and congratulations on the stunning success already of this pioneering mission.

Nicola Fox: Thank you so much.

Nour Raouafi: Thank you so much. And it's amazing that after six years we are achieving this, it's just amazing.

Mat Kaplan: We're going to get to the science, it's moments away, but I have to start with that utterly amazing, that jaw-dropping video. And I'm sure you know the one I'm talking about, actually touching the sun as you put it, Nour. My colleagues and I at The Planetary Society including our boss, Bill Nye, we were profoundly affected by that video, that first flight through the sun's corona. They agreed with me when I said I couldn't think of a space video that is more beautiful, more jaw-dropping or more memorable. If I could, I would nominate it for an academy award. Everybody needs to see that video.

Nour Raouafi: Thank you. It's fascinating that just a few years ago before the launch, when we were talking about the mission saying Parker Solar Probe at a certain point will be flying through the structures that we see during total solar eclipses. Personally, I think of it as true, but when we saw it, we saw structures that are flying above and below the spacecraft. It is just amazing. It's kind of surreal that we have something that we were [inaudible 00:05:21] it just few years ago and now it's just flying through the structures that it's just fascinating.

Nicola Fox: I have to completely agree with you. The first time Nour showed it to me, I was in his office and he just had it up on this big monitor. And I kept saying, "Stop, wait, go back. No, no, wait, stop, go back, go back. I need to see that bit again." And it was just so incredible. I remember saying, "Oh my God, we just flew through this [inaudible 00:05:45] and go back, I need to see the whole thing again." And so it literally was like I wasn't prepared for it. He just said, "Hey, I've got something kind of cool to show you." Because Nour's very laid back about these things. And I just was again, doing back flips practically in the office over this amazing video.

Nour Raouafi: And you can imagine when Nicky's excited about something, that's just [inaudible 00:06:08].

Mat Kaplan: Well as one of my colleagues put it once, Nicky was over the sun at your launch of this mission.

Nicola Fox: Yes. Yeah. Frequently, I am.

Mat Kaplan: The great MaryLiz Bender, a friend to both of us I know, I got to say, it would've been fine if we had just seen those particles of the solar wind flying past us. But then, I mean, my God, there light years away without being much affected by what we see surrounding your spacecraft is the Milky Way visible through all of that chaos. It's just spectacular.

Nicola Fox: Yeah, it really is.

Mat Kaplan: Nicky, we were talking just before we started recording about the last time, actually a couple of times that you were on Planetary Radio, when you spoke to my friend and former colleague, MaryLiz Bender, who interviewed you at the August, 2018 launch of Parker Solar Probe. I know that was also when you transitioned from being the mission's project scientist, the job that Nour now has, to leadership of the Heliophysics Division at NASA. Do I have that right?

Nicola Fox: Yes. That's right. About three weeks after Solar Probe left the pad, I left my own pad and I moved down to NASA headquarters where I've been ever since, running all of the heliophysics division. So a tremendous portfolio with so many great missions, but Parker Solar Probe providing those inner measurements of our Heliosphere and then of course having Voyager all the way out in interstellar space. And so we really do cover everything with heliophysics.

Mat Kaplan: I hadn't thought about that. Here we are touching the sun. And at the other end, we're feeling the end of the sun's influence across the galaxy.

Nicola Fox: Absolutely. It's kind of a profound feeling that we are making these measurements and then eventually the measurements that we're making with Parker Solar Probe Voyager is going to see all the way out there. So it really does encompass everything in our solar system.

Nour Raouafi: It just takes few years to get out there. That's-

Nicola Fox: Yep. Eventually we'll see it.

Mat Kaplan: Let me ask both of you, why this mission and the goals that it had, why was it the goal of so many heliophysics researchers, heliophysicists like yourselves, for so many years being able to achieve this?

Nicola Fox: Because it really was the most important question. How does our star work? How does it influence us here on Earth? How does it influence our entire solar system? We've looked at the sun in every different wavelength. I mean, we've done a tremendous amount of research. So even though it was the highest priority, 60-some years ago, we've done a lot of research in that 60 years. We didn't just sit there saying, "Well, we'll wait for the mission to launch. Scientists were really working on as many of the different problems as they can. And we'd sent missions in as far as the planet Mercury, but we'd never been able to travel through that region where all of this physics is taking place, all the secrets are kept of the star. And it just took that long to get technology, to be able to allow us to do that mission.

Nicola Fox: So it remained the highest priority because it was a question that really could not be answered or a set of questions that really could not be answered without this daring mission. And no matter what we did, it was almost like the more research we did, the more tantalizing and the more important this question became because you find out something, but you still need to know that underlying principle. And so it's like looking out of your window and you know you can see largely what the weather is like, but you don't know the temperature, you don't know how hard the wind is blowing, until you go out into that environment. And so we've stand at the sun. We've looked at it in all different ways, but going up and visiting, it was the only way to really answer these questions.

Nour Raouafi: These problems we are dealing with are not easy problems at all. They are extremely challenging. As like said, if you don't really go to the source where they occur, we will not get much insight into what is going... Because if you take the solar wind for instance, when it leaves the sun, it propagates to Earth and beyond. It gets processed along the way. And by the time it reaches Earth, all the signatures of the physical processes that gave it birth and accelerated it to very high speeds, they are all raised by the journey. So we need to go there.

Nour Raouafi: There is also another side to Parker Solar Probe, which is usually we don't talk much about it, but it's extremely important as well. Remember in the late '60s, early '70s, when we landed men in the moon, that was a huge achievement. The achievement is on the technology side, basically that opened the gate wide open to space exploration. And we visited all the planets, maybe moons and everything. The only thing, the only object in the universe that we did not visit yet is a star. We are doing it with Parker Solar Probe now, and that is not an easy thing to do.

Mat Kaplan: Because our sun is no more than just a run of the mill middling star, right? And we know of course that there are trillions, if not hundreds of trillions of them across the universe. So I assume that we are learning far more about how all of them work by studying the one that happens to be in our neighborhood.

Nicola Fox: Yes. Absolutely. I joke with Paul Hertz, who's the head of astrophysics, all the time that the sun is a star too, and he says he's always jealous, because we have so many photons coming from our star and the ones that he looks at, the very photon challenge. But yes, this is the one that we can go up and visit. And even though as Nour correctly said, it's incredibly hard to go and visit this star. It's a lot easier to visit this star than to visit the next one. And so we really are doing everything we can to learn about and characterize and fully understand our star and then use it to help understand other stars. We Know that other stars in other stellar systems, we know that they have flares. We know that they have storms. We know that there's some similarities, as you say, our star is an average star. It's kind of right in the middle of that sequence. And so yes, totally applicable to what we're doing to other astrophysics and other stellar systems.

Mat Kaplan: There's an interesting point made on the mission website, which of course we will link to, the Johns Hopkins University applied physics laboratory website, and also NASA resources and our own Parker Solar Probe pages at This interesting point is made that, of course, at least at this point, maybe this will change in the coming years, but right now the only star we know of that has been able to support life on the planets that surround it is the same one that you're visiting right now. So it sounds like there's a possibly at least an astrobiology element to this mission.

Nour Raouafi: Absolutely. Studying the sun up close and understand how it interacts with its planetary system. And in particular, the habitability zone, which is our Earth here. It is extremely important because once we understand how the sun interacts with the Earth and the other planets, we may actually get insights into other planetary systems in the universe and figure out which ones probably can have habitability zone that can harbor life. And as you mentioned earlier, there are trillions and trillions of galaxies. And obviously each galaxy has trillions of stars in them. And many of them has planetary systems around them. The big question is, are we alone in the universe? Personally, my instinct says probably we are not, why should we be the exception? But we might be, but there are big possibilities there that is life there.

Nour Raouafi: And coming back to the sun, as Nicky was saying earlier, understanding how the sun works and how it affects us here on Earth, it's crucial to astrophysics, to everything we study in the universe. And let me say one more thing. Usually when we talk about the sun and how its influence on us here on Earth, we usually have probably a negative connotation to it. That is space weather can affect space systems, affects us, the power grid and all that. But actually it has a positive side that we often don't talk about. Without the solar activity, that is flares and CMEs, life may not have kicked off on Earth. That activity was necessary to kick off life on Earth here.

Mat Kaplan: You're going to have to go further into that because I have always assumed... I mean, we talk now about those red dwarf stars, which are extremely active and that that may interfere with the generation of life in those other solar systems. How does a solar flare, something that can cause such havoc, how might that have contributed to the start of life on Earth?

Nour Raouafi: When you have solar flares and CMEs, they bring all the isotopes to the Earth's system. And that actually helps kick off the chemistry in the atmosphere, but mainly in the oceans. And that's what's crucial to kicking off life out there. And there is research in this that's saying without probably the solar activity, probably life would not have existed in Earth.

Mat Kaplan: Other than the evidence that is before our eyes in that wonderful video, how do we know that Parker Solar Probe has actually entered the corona, that it just has touched the sun, in your words, Nour?

Nour Raouafi: The easiest way is the video you mentioned when we are seeing that Parker Solar Probe is gliding through the structure. It's fascinating. And we know the structure belonged to the solar corona. So we know that, but the tangible evidence that we got, we got actually from the fields and particle measurements. And there is a boundary that separates the solar corona from the solar wind. The solar corona is magnetically dominated and it rotates rigidly with the sun. The solar wind is not. And when we cross that boundary, we know it from measurements of the magnetic field and the densities of the solar wind. We can compute what we call the magnetic Mach number. And when it is below one, it means that we are into the solar corona. That's actually the hardest evidence we got that we actually transitioned into the solar corona.

Mat Kaplan: Nicky, I'm going to stretch a metaphor here because when I read about what Nour's just talked about on the website, this border between the sun's atmosphere, the corona and further out in the solar system, it brought me back to Voyager. And I was thinking of detecting the heliopause, which we now believe... Is it both of the Voyager spacecraft or?

Nicola Fox: Yes.

Mat Kaplan: Yes. Have now passed. Is that in any way, a fair comparison? I don't think it's magnetically related.

Nicola Fox: It's a comparison in that it's a boundary, and it's a boundary between very different conditions. And of course, with Voyager, we saw all of the sun's activity kind of switching off and the activity we expected to see with interstellar space coming up sharply, we were able to see it better with Voyager too, because of the instrumentation that was still working. But yes, we knew we'd crossed the boundary. Now, you know you crossed the boundary, you have to double check, triple check, make sure all of your instruments are seeing the same thing. One instrument alone can have signatures that make you go, "I think we crossed the boundary," but you really need to see all of the coordinated measurements to make that full determination.

Nicola Fox: And that's why Solar Probe is so great because we have all of the complementary measurements that mean that we can definitively say it. We saw the magnetic fields increase as we had predicted it would, we saw particular wave structures that were shimming along this increase in the magnetic field. And we saw that with our magnetometers. We saw that with the wave antennas, we saw the plasma measurements do exactly what we thought they would see as the density increased too. And so it's putting all those pieces together.

Nicola Fox: But yes, it is a boundary. It's not a solid boundary. The sun doesn't have a solid surface. The corona doesn't have a sharply defined... It's really a surface, and so we crossed it at one particular location on this orbit that we are discussing. As we cross it on other ones, we certainly don't expect to see it at exactly the same point because it's really like a rippling surface. And so just like if you dive into the ocean, you dive in at different heights of the waves, depending how the wave is cresting at the time. And so that's basically what we're doing with Solar Probe. We dive into the corona beneath this boundary, and we look forward to doing it on all of our upcoming orbits, she predicted bravely.

Nour Raouafi: And I can tell you actually, we actually did it. So we did it actually for a longer time. And for what Nicky said earlier, is pretty why it took us so long to announce the news because we wanted to check and recheck and recheck everything that we are calling is right. Because this is an important milestone for the mission but also for science. We are actually entering in [inaudible 00:19:24] of the solar wind. We are flying through the region where the solar wind is bored and gets accelerated. And this is extremely important. We have been waiting for this for 60 years now, and we are doing it.

Mat Kaplan: Obviously, a lot of this is coming from knowledge that we already had, what we thought we could expect, but you're also being surprised by some of what you're finding at the sun. And I'm thinking in part, you made me think of it, Nicky, because you talked about that very uneven surface, with quotation marks, of the corona. And there are some animations and illustrations of this on the website, it's quite wavy. It's quite irregular. Do we know why that is? I mean, in a way it seems natural, but I wonder if we understand the mechanism behind it.

Nicola Fox: Well, I think if you look at the sun, I mean, if you look at beautiful images from like SDO for example, you see all the different activity, you see bright spots, dark spots, and the sun is always boiling and churning and it doesn't have a solid surface. And so what you see as the surface is just where your eye kind of says, "Okay, that's where the surface is." That's where you are sensitive to the light. The actual surface of the sun is also wavy and undulating and continually moving. And so it's really driving the corona. So the corona gets held at a certain distance above the sun by various different processes. As those processes change, the location of the boundary will also change.

Nour Raouafi: It's like you have the ocean, but you have a gazillion of tributaries that are all getting in the ocean, and all of them have different properties in a way. So you don't expect this boundary to be the same for all of them because they all have different properties.

Mat Kaplan: It's a chaotic system, right?

Nicola Fox: Very.

Mat Kaplan: A lot of factors here. Is there a way to categorize the strength of the magnetic field of the sun? I mean, is there a comparison that could be made to Earth's magnetic field because clearly, this magnetic field is incredibly powerful and is driving a lot of these phenomena that you see as Parker Solar Probe dips down into the corona.

Nour Raouafi: Yeah, absolutely. In terms of the physics itself, physics is more or less the same, but these are different regimes. For the Earth, the magnetic field is mostly static, at least in the inner part of it, it's mostly static. For the sun is completely different. The sun is changing all the time. You see the sun today is different in one hour and it's different tomorrow and it's different next week. So it's not the same at all. And that is actually what is fascinating about stars in general, they are changing all the time and they can do amazing things that some of them you can expect, some of them you don't expect. And that's exactly what we are seeing with Parker Solar Probe. We are seeing so many things that we didn't even imagine them before. They are absolutely completely new to us.

Mat Kaplan: I'd like to talk about some of those surprises that you're running into. It has been given by you and other heliophysicists this fascinating, but very descriptive name. Tell us about switchbacks.

Nicola Fox: So switchbacks, that was something that we were not expecting. The very first orbit, we saw those switchbacks. And I remember being at the AGU meeting, American Geophysical Union meeting, with a standing room only packed, and it was the first few bits of data that we had because we'd only just got this data down. So it was literally hot off the press. I remember this particular plot being shown and it just showed the magnetic field line. It's a simple plot. It's a black and white line plot. And it showed these things and you could hear audible gasps in the room because A, it was the first time you're actually seeing the sun's magnetic field up close.

Nicola Fox: And so that's a powerful moment as well, but just seeing how dynamic it was, because I think everyone thought, well, you might see a current sheet crossing. You might go from super above to below and you'd see a change, but this was just going all the time. Again, that took a little while, we had to get the other data sets down and look at how the plasma was changing in response to these magnetic fields. And so what we actually saw was these sort of S-shaped curves in the magnetic field, which is really surprising because now you have plasma, you have things moving back towards the sun. I mean, if you think about it, you expect it to come out. Now it's going back and curving back out again-

Mat Kaplan: Like a switchback on a mountain trail.

Nicola Fox: Just like a switchback. Exactly. And it's not clear how they form, because if you think about taking a garden hose and twisting it, you actually have to put quite a bit of energy in to get that garden hose twist. And the first thing it wants to do, spring back out again. And so we knew, well, hey, whatever's causing these as soon as they relax and you can see them relaxing in the data as they move further out, wow, that's letting out a ton of energy because somehow you put energy into the corona, into the magnetic field. It relaxes, it lets out energy. And there's your smoking gun for why we're seeing energy deposited in the corona. That was a big, big surprise. And that was surprise number one on orbit number one. And that was when you knew this mission is going to give you more and more surprises and more and more fabulous data, the longer the spacecraft flies, because no one expected anything like that on the first orbit.

Nour Raouafi: The meeting Nicky was talking about, actually the session at the AGU, was talking about was in Thursday morning. It was 8:00 AM I believe. But two days before, it's in Tuesday when we got the data and we were sitting at [inaudible 00:25:15] and when we saw that plot Nicky was talking about, the initial thought was, what was going wrong with the instrument?

Nicola Fox: Exactly. Yes. Exactly.

Nour Raouafi: [crosstalk 00:25:24] it took us probably 10, 15 minutes to realize no, the instrument is actually right. It's working perfectly fine. And what we are seeing is new physics, it's something. And while these switchbacks... I mean, we saw them before with other missions, but we see one every now and then. They are so rare, further out in the solar wind. What Parker Solar Probe showed, as Nicky said earlier, you see a jungle of them when you get closer to the sun. The mystery about them is where do they form? How do they form and how do they evolve in the solar wind? As Nicky pointed out earlier, the energy they carry out will dissipate at a certain point. But how that is done, it is not clear yet.

Mat Kaplan: Does this possibly partially answer that question that heliophysicists have wondered about for over a century, which is, how can the inner surface so called of the sun be what? Maybe 10,000 degrees Fahrenheit, but the corona is millions of degrees harder? Could this be part of the explanation?

Nour Raouafi: It could be, but we do not have a firm answer. I mean, what is the contribution of the switchbacks to that phenomenon? It is not quantified yet. We are moving toward that goal, but what is clear, they are a potential contributor to the heating and the acceleration of the solar wind. Definitely, because as Nicky said earlier, they carry a ton of energy with them. And when you move further out into solar wind, these switchbacks kind of disappear. So they must have dissolved. They must have dissipate somewhere through turbulent processes and things like that. And all that energy they carry with them, it is transferred to the plasma in the form of heat and speed. And that's actually links back to the corona heating problem that was discovered in the late '30s of the last century and also the acceleration of the solar wind that is over 60-year-old problem.

Nicola Fox: We call it the smoking gun. It's definitely not fully answered yet, but that's why the mission is a seven-year mission. If you thought you were going to answer everything on orbit one, you wouldn't need to keep going in, but as Nour alluded to, the closer we get to the sun, the more of these switchbacks we see and they're getting larger. And then we actually, I think as we're getting closer, we may actually see less of them.

Nour Raouafi: One thing is fascinating about this mysterious phenomenon that we are seeing of switchbacks. There are a big debate now, where do they form? There is one group that says, "Well, they form at the base of the corona where the solar wind is bored and they get convected by the solar wind." Another group says, "No, no. That's not the case. They form in-situ in the solar wind, so that's a natural evolution of it." And in a way, if we solve that problem of the formation of the switchbacks, we might actually be selecting between the two most prominent theories of the solar wind. That is magnetic filter connection in turbulence. I mean, for years and for decades now, we don't know which one of these theories is probably the right one or that contributes most to the acceleration of the solar wind.

Mat Kaplan: So it sounds like you have the potential here to solve... I mean, this could be part of Parker Solar Probe's legacy, figuring out which of these two models is correct or more correct. I mean, it makes me think of back when we didn't know if craters on the moon were caused by volcanic activity or meteors, and that has been resolved. Will this be of that sort of significance in heliophysics?

Nicola Fox: Definitely, if not even more important to heliophysics, it really is the key question for us. And Nour is absolutely right. Right now we have two theories. We hope we will distinguish between them. There could be a third theory. It could be a combination of both with one being a higher contributor in certain conditions and the other being a higher contributor in other conditions. And so this is what we really need to unpack, but boy, the switchbacks are a great signature to get us started.

Mat Kaplan: Nicky Fox and Nour Raouafi will add more illumination to our understanding of the sun and the Parker Solar Probe in less than a minute here on Planetary Radio.

Casey Dreier: Hi again, it's Casey Dreier, the chief advocate here at The Planetary Society. Our 2022 Day of Action is set for March 8th. This is your chance to advocate on behalf of space science and exploration. If you've heard us talk about how effective and just personally rewarding our past Days of Action have been, this event is for you. Learn how to participate in this virtual online experience by visiting If you live in the United States, we'll book your congressional meetings for you and also provide you expert training, so you can be the best advocate possible. If you live outside the U.S., you can still make your voice heard on March 8th. It all starts at Join us as we speak out for space.

Mat Kaplan: Just to stick with these switchbacks for another moment, how far down have you been able to trace their generation? Because it looked like, and as you were saying, Nour, in one of the theories, they're coming right from... I'll use the word gingerly again, the surface of the sun below the corona, where talk about visually impressive, that's where these things called supergranules are, which really have to be seen to be believed?

Nour Raouafi: When we look at the solar surface, the magnetic field element that are brought from the interior of the sun, they organized in a network that we call supergranules. These are huge cells, and the magnetic fields are concentrated on the boundaries of these cells. And the magnetic field when it expands into corona, it forms what we call funnels. And these are magnetic field structures where the plasma is flowing outward all the time. So with the most recent Parker Solar Probe data, we actually could trace signature of the switchbacks to these supergranules. They have some correlations between them. And that is the supergranules is a potential source of the switchbacks. If I put it in a different way, that is probably favoring more the connection scenario, magnetic filter connection scenario over turbulence, but that is not the full story, because from earlier data, there is other evidence that's saying probably the switchbacks are also formed in-situ. So this conundrum of the sources of switchbacks, we are far from solving it now. We will continue with it for a while.

Mat Kaplan: Such is science. Nicky, what are some of the other surprises or data that we are getting back from Parker Solar Probe that you are really proud of?

Nicola Fox: It's somewhat related to the switchbacks, but I think the finding that somewhat close boundary or very sharp boundary between where the solar wind is accelerating and moving directly radially away from the sun as to where it's still moving, rotating around with the sun as a solid body. We didn't expect to see that so early either. And that's, if you think about Justin Kasper in his great explanation as you think of a child on a merry-go-round or a carousel going round with the carousel. But if they jump off or they took a run and jumped off, they'd keep going straight, but the carousel keeps going round. And we saw that at a pretty sharp boundary and further away from the sun that we were expecting to see.

Nicola Fox: And again, this is all done in the early orbit. So things where we thought we'll get to characterize the outer area of the corona for a couple of orbits, and then we'll finally do enough Venus flybys that will get into that region of interest. We were in the region of interest from the very beginning. So all of these things were seen on orbits one, two and three. So that was before the second Venus flyby, before we took the next step in that we were seeing all of these things. So that's probably my favorite one that tells you about the history of a star and can tell you about how the star matures, that probably was my favorite one, other than the spectacular images that you've already talked about.

Nicola Fox: And I think seeing the Milky Way, again, you mentioned that in the video, but we saw the Milky Way that was our first light image from the coronagraph was a Milky Way image, an absolutely stunning image from a white light coronagraph. So some of those things are just really beautiful and we're very proud of all of the instruments and all of the scientists and all of the instrument teams that are working so diligently on not just the science, but also producing the data for countless other scientists to work on as well. So it's just a great team.

Nour Raouafi: The phenomenon that Nicky mentioned of the excessive tangential flows further out in the sun is extremely important. And it's not only important for the sun. It's important for stellar physics in general, because one of the big problems is how stars lose angular momentum. When stars are born, they are rotating very fast, but as they age, they slow down. For the sun, we rely on models. We don't have measurements at all. And Parker Solar Probe is providing us with the very first measurements, and the measurements that Parker Solar Probe is giving us, they are quite different from the model that we thought is right. I mean, it's amazing, if that holds, we have to revise all these models. And by the way, the stellar models are all built on the solar model. So we have to revise all that in a way.

Nour Raouafi: Another thing we thought that we would have some evidence for it late in the mission is what we call the dust-free zone. And the dust-free zone was predicted over 90 years ago in 1929 by a physicist called Henry Russell. And he was studying micro-sized dust around stars. And he was predicting that should be a zone around each star where there is no dust at all. In a way, these dust particles, when they get close to the star, they got so hot to the point of sublimation. And once they sublimate, they get cleared out by the solar wind and other phenomenon. So there is a vacuum in terms of dust around the star, but for 90 years, we looked for it over and over and over again, but we had no evidence whatsoever for it, but from orbit one, Parker Solar Probe gave us the very first hand that the dust-free zone exists around the sun. And by the way, that discovery was not even in the prime science of the mission.

Mat Kaplan: I may come back to dust because I know it can also be a challenge for you, for the spacecraft. But I just wonder before we move on, are there any other findings you would want to call our attention to as the Probe continues its work?

Nour Raouafi: Waves is one of the big things we are looking for in plasmas in general, in particular, the solar wind, because waves, they are one of the potential phenomena that will heat and accelerate the plasma because once the wave loses energy to the plasma, that's where it goes in heat and acceleration. With Parker Solar Probe, we see all sorts of waves on the solar wind, which is expected. But one thing in particular, it's very eye-catching. When we have the quiet periods of the sand, we see a lot of waves, but when the switchbacks come in, these waves kind of disappear. We don't really understand why that happened. And it's another side, if you wish, of this mystery of the switchbacks, why they behave in that way, why the plasma behaves in that way when we have switchbacks and when we don't have them, that's another fascinating thing, but we don't understand it yet.

Mat Kaplan: Nicky, you already mentioned SDO, Solar Dynamics Observer, I believe, that other farther-out spacecraft that is staring at our star. I wonder how you see Parker Solar Probe as complementing, as being part of an integrated study of the sun. That includes SDO, but also the great solar telescopes down here on the surface of our world.

Nicola Fox: Yes. So actually one of the great things about being the heliophysics director is I get to play with all of these spacecraft and put them together in interesting ways. And so it would be remiss if I didn't mention the ESA-NASA mission, Solar Orbiter, which launched in 2020 and is now coming in for their second closest approach of the sun themselves. It's a very different kind of mission. They're further away from the sun. They'll be around Mercury. But the reason for that is because they have all these spectacular cameras and remote sensing instruments that you couldn't have them so close to the sun. So we need to keep them a little further out. But the synergy between the two missions is just staggering. And to have them flying at the same time is just wonderful.

Nicola Fox: We will be really up close flying through these structures while Solar Orbiter is imaging those structures. And as they do their maneuvers, we use Venus to take us closer and closer to the sun. They're using Venus to take them out of the ecliptic. So they'll actually be able to view the poles of a star. And that's the first time we've really viewed the poles of a star. And so now you're looking at maybe activity from the next solar cycle that may move down to the equator over the course of a solar cycle. Putting these two together is just amazing. DKIST is the new telescope, ground-based telescope, will take unprecedented measurements of our star. And so to have these three sort of giant observatories that are just answering these incredible questions and have them all working together is just spectacular.

Nicola Fox: Every time we have a campaign where the footprint of Parker Solar Probe is visible from the Earth. So when that closest approach is on the Earth's side of the sun, we actually have campaigns where just about all of the ground-based solar telescopes are operating and taking what we call campaign data. They're really focusing on the science that will really add to Parker Solar Probe. We've had a couple of those, the upcoming closest approach that will be occurring next is one of those amazing cases. And all of those solar telescopes will be staring at the sun and really characterizing what Parker Solar Probe is flying through. We have new missions that we've just confirmed that we'll be also adding based on the great work that Parker Solar Probe is doing now, honing their science questions to take into account the new discoveries of Parker Solar Probe that were not available when they were writing their proposals because we hadn't launched yet.

Nicola Fox: And so we have punched for small spacecraft that we'll be looking at the sun from the inside out, really focusing on the region inside and how these things are born. We have sunrise, six cube sets that will go out and separate and form one giant radio receiver dish. But by adding the data altogether, something we could never have done a long time ago. But again, they're focusing on the waves that Nour talked about, and there are wave signatures of these big events coming out. So Parker Solar Probe already having a profound effect on our future missions.

Nour Raouafi: I will try to bias the discussion toward Parker Solar Probe, because I have to be a little bit [inaudible 00:41:16] and I'm objective here. When we look at data from other missions like SDO, for example, Solar Dynamics Observatory, we always have in mind what Parker Solar Probe is observing when we are looking at that data, because we are trying to link both what Parker Solar Probe is measuring in-situ and what SDO is observing remotely. And now we are getting closer and closer to the sun. We are seeing that link becoming stronger and stronger. We know the signature of the physical processing mechanisms that are occurring at the base of the corona and what are the effects of the solar wind. So we see it now, but let me also come back to the campaigns that Nicky mentioned earlier, and this is just for history.

Nour Raouafi: The first one, the first encounter that gave us opportunities for synergies with the ground was encounter four. I sent an announcement, ask a basically soliciting support for Parker Solar Probe. And honestly, we were hoping for a handful of observatories to support us, but we got actually over 50 observatories worldwide supporting us. These observatories are doing all sorts of observations to support Parker Solar Probe. What that tells us that the community is so enthusiastic about Parker Solar Probe and they are all coming together trying to understand how the sun works and how to get that basically the all type of data that will help us to get there.

Mat Kaplan: When I hear these bits of this ongoing story, the study of our own star, I cannot help the thinking of the scientists and observers perhaps across all of human history, who've been looking up at it and wonder, hopefully not staring right at it. George Ellery Hale is a great example. I mean, he's mostly known for building the biggest telescopes of his day, but his own research, his lifelong fascination was the sun. And I cannot help but think of how much he would love the work that you are doing with Parker Solar Probe in coordination with all of this other great science that is underway. Nicky, do you ever think about that?

Nicola Fox: Oh, actually I do. I mean, I often describe heliophysics as a somewhat new term to describe what we do. I often say probably it's the oldest branch of science because the first people looked up at the sun and thought, I wonder what that is. And they knew it had a profound effect on what they were doing, even though they may not understand it. And so that sense of wonder of this thing in the sky that is actually determining our quality of life here on Earth, it just really to me, makes us the oldest branch of science. Also, I keep in very close contact with Dr. Eugene Parker. And I recently went out to visit him at the end of last year to actually present him with his Crawford Medal, which is very big deal. And I got to go do that. And he is absolutely captivated by everything that we are doing. He wants the latest papers. He wants the pre-print.

Nicola Fox: I often send him the pre-prints of papers and I'm like, "Don't tell anyone about this. You can read the pre-print, but we haven't published it yet." And he will often engage with the researchers themselves and say, "Hey, I'm really excited about this." Or, "Have you thought about doing it this way?" And so just having him still so excited about the mission that bears his name, I mean, who wouldn't be excited if you have a mission named after you? But he is just really in there and talking to some scientists who have been in the field for a long time, they'll just say they're so excited and so grateful to see this mission actually flying during their lifetime, because you don't know that's going to happen. And they're the ones, the giants that came up with the science that we do. So I think it's just a very, very profound mission.

Nour Raouafi: So Nicky, at 95 years old, would you still describe Eugene as a kid in a candy store when he sees data from Parker Solar Probe and things like that?

Nicola Fox: He is. I went out, I think on the one-year anniversary of our launch, I went out and actually showed him some Whisper movies, so-

Mat Kaplan: That's one of your instruments, of course [crosstalk 00:45:31].

Nicola Fox: That's one of the instruments that actually... I'm sorry. Yes. The white light imager that took the movie that you were talking about at the beginning. Showing him those images and actually that image with the Milky Way through it, and you can see all of the planets in there and he was just like, "Wow, that's what the solar wind looks like." And yes, the more data he gets, the more excited he becomes, I think so. So definitely even at 95 years old, still super excited about everything that we do. Even he'll sort of, "Come, come tell me, come tell me what's going on. And whisper in my ears so nobody else hears, but tell me what's going on." So yes, he's fabulous.

Mat Kaplan: I get the strong sense that I am talking to two more of those kids in the candy store, Nour?

Nour Raouafi: I think we are all kids after all. I think we are all excited by stuff we are looking for. It's fascinating. Well, I think that's our job. That's what we are doing. We are doing science. And what is fascinating to me is the unwavering enthusiasm of the whole team from the get go until now and in the future. It is amazing how these folks are basically putting everything behind this mission. Just few days ago, when we had a small snowstorm here in the middle of the night, there was something that needed attention right away. And we had folks just drove through the snowstorm to the mission operation center to deal with it. That was in the middle of the night. It was at 2:00 AM. And it's just fascinating how everybody wants to see this mission be the mega success it should be. And there is no reason it should not.

Nicola Fox: And I think also, I don't want to miss out on the fact that we're doing Venus science as well. When we fly by the planet Venus, we were able to actually keep the instruments on. At first, we thought that we may have some power margins and we may need to switch them off, but we were able to keep those instruments on, even from the very first flyby, we've had one where we've taken spectacular images of Venus, again, with our white light imager. So the Planetary community is excited about the results that Parker Solar Probe is giving them from the planet Venus. So we really do cover everything. We're helping the astrophysics with the sun as a star too. And this is rewriting the models for other stellar objects We're providing support to the Planetary. And we're telling everybody more about how planet Earth responds to what is coming from the sun.

Nicola Fox: So we really are covering everything. And you asked earlier about how the sun and the Earth's magnetic field compare. I think of the Earth's field, it's about half the overall half the magnitude of the sun's magnetic field, but the Earth's field is there to protect us. The sun's magnetic field is causing the chaos that the Earth's magnetic field is protecting us from. It's just a relationship between those two magnetic fields, both doing very different things, both having a big effect on our ability to live here.

Nour Raouafi: Talking about Venus and just as a teaser, there is a new discovery that we will announce in the next few weeks. It's fascinating observation. We cannot talk about it now, as Nicky was [crosstalk 00:48:44].

Mat Kaplan: Nicky held a finger up to her mouth, she should be very careful, Nour.

Nour Raouafi: It's coming and it's fascinating. And as Nicky said earlier, this is all bonus science, and there is a ton of it out there.

Mat Kaplan: I bet you are delighting the teams behind those three new missions that are headed to Venus, as you delight the rest of us with everything that you are revealing in the bright light of the sun, I hope that Parker Solar Probe can keep this up for many, many more encounters. I know it has to be a very difficult environment, but my goodness, those engineers on the mission have certainly served all of us well. And especially you, the scientists who are now revealing our star to us, thank you so much for this conversation and best of continued successes as Parker Solar Probe continues its work.

Nicola Fox: Thank you so much. It was a pleasure to talk to you.

Nour Raouafi: Thank you so much. And the goal I think is to make Parker Solar Probe a mission for the ages. We want people to be working with Parker Solar Probe, 20, 30, 40 years from now.

Nicola Fox: Absolutely. Don't forget. It's the coolest hottest mission under the sun.

Nour Raouafi: There you go. There you go.

Mat Kaplan: It's time for What's Up on Planetary Radio. So I have, sitting across from me, virtually, the chief scientist of The Planetary Society. It's Bruce Betts. Let me read you something. This came from Steve Sheridan in California. Mat and Bruce, love what you two are doing for the space community informing and entertaining us every week. Please keep up your excellent work. Nice, huh?

Bruce Betts: Yep. Checks in the mail.

Mat Kaplan: Yeah. Thanks uncle Steve. Welcome.

Bruce Betts: Thank you. All right. Well, let's do our sky thing that we occasionally do every week. I don't know what I did in the evening, but I have scared the daylights out of the planets, they're all running till the morning sky and knowing there is no way I'm going to follow them there. We still have Jupiter being brave in the low in the west, in the early evening and to its lower right, Saturn. Mercury, even coming to play with Saturn for a few days, but then everyone's running away. Venus is already taking the bus, the boat, whatever, it's popping up in very low in the pre-dawn east, but it'll rise very quickly. By the end of January, it'll be quite easy to see and we'll be catching up to Mars that's just been chilling in the east, in the pre-dawn sky.

Bruce Betts: So still we're split in evening and morning, and we'll be doing morning for all these planets within a few weeks. This week in space history, a couple cool things from the [OTS 00:51:28], the 2000s. 2005 ESA's Huygens lander, part of the Cassini–Huygens mission went through the Titan atmosphere over a two and a half hour period and successfully even landed on the surface of Titan, a billion and a half kilometers away from Earth. And then 2008, MESSENGER did its first flyby of Mercury solving my enormous curiosity and other people's for what that other half of Mercury looked like, since we only saw roughly half of it from Mariner 10.

Mat Kaplan: Two great accomplishments.

Bruce Betts: We move on to [inaudible 00:52:08].

Mat Kaplan: It's like the cowardly lion, he's trying to roar.

Bruce Betts: All right, here we go. I think you'll like this one, Mat. It's just odd enough. I did some calculations. The International Space Station has a mass approximately equivalent to a single-story house with an area of 465 square meters or 5,000 square feet. So it's mass, if you had dropped it on the Earth, that would have the same weight as a single-story 5,000 square foot, 465-square-meter house.

Mat Kaplan: Which is a good sized house. Somebody who has a house that's 5,000 square feet, maybe, especially if you dropped it into the Hollywood Hills or Bel Air or someplace like that, could afford to build a house that looks just like the International Space Station.

Bruce Betts: Well, we'll see if we prompt any of our well-to-do listeners to do such a thing.

Mat Kaplan: Oh, man. We put the bug in their ear.

Bruce Betts: Yeah. Like that thing and check outs here in Star Trek too. Ugh. Anyway-

Mat Kaplan: Oh, yeah. Oh, gross.

Bruce Betts: It's horrifying. Couldn't lick an earwig in the... Nevermind. All right. We move on-

Mat Kaplan: Scared the daylights out of you, huh?

Bruce Betts: Yeah, exactly. I almost went to the morning sky. All right. Trivia contest. I asked you, how many deep space, by which I meant to the moon or beyond, launches were there in 2021. How did we do, Mat?

Mat Kaplan: Notice how he repeated launches, because we think some of you might have counted well, a couple of spacecraft as separate launches when they were really on the same rocket, but more about that in a moment. Here is an answer from our poet laureate, Dave [Fairchild 00:54:14], in Kansas. 2021 had launches, rockets flying high. There were just a trio that have left our friendly skies, by which I think he means between here and the moon. Lucy left for Trojans, DART for Didymos. Who's three? Her golden hexagons of flame, we have JWST.

Bruce Betts: I hope its hexagons don't catch fire. It'd be tough in space.

Mat Kaplan: We're going to get another rhyme of three and JWST before we're finished here. But was that correct?

Bruce Betts: That is correct. That is correct. Lucy, DART and JWST. And DART includes another spacecraft along with main spacecraft and Italian CubeSats.

Mat Kaplan: Here's our winner, Joseph [Lad 00:54:58]. Congratulations, Joseph. First time winner. He has been listening and entering for over five years. I believe he's also a proud member of the society. He's in Nevada. He says I found three. Sure enough, Lucy, DART, JWST. Hope I'm not missing any. He also adds looking forward to the Day of Action, as are we all, Joseph. So I guess he'll be joining in where people can learn about that day of advocacy for space exploration at All one word. Thanks for allowing me to throw that in there, Joseph. He's going to get one of those 2022 International Space Station wall calendars that we've been talking about. We're at proudly on your wall, Joseph, and thanks very much for listening.

Bruce Betts: Yay.

Mat Kaplan: A lot of people suspected that you were up to something beyond what they could easily find. Burton Caldwell in New York said, "I think there's a trick in this question we're all missing." Mel Powell in California made it much more overt. He said, "I'm terrified that I'm wrong. Curse you, Bruce Betts, evil genius. I will never let you toy with my emotions again." And then, narrator, he would enter the contest the very next week and let Bruce toy with his emotions.

Bruce Betts: See the great thing now is I've toyed with everyone's emotions so much that even when I ask what is basically a straightforward question, they actually become suspicious that it's not straightforward.

Mat Kaplan: If you ring a bell, they may all start drooling too. A little bit of [inaudible 00:56:42] there. I noticed it at the end. Ben [Drought 00:56:44] in Iowa, he even gave us the rockets. Atlas 5 is what took Lucy up. It was a Falcon 9 that DART was on the top of, and that other Italian CubeSat. And an Orion 5 of course, as many of us saw, big Orion 5 that set the James Webb Space Telescope on its way. We had this last contribution from Jean Lewin in Washington, all in all for orbital, 146 were tried. Most were planned for low Earth realms, a small percentage though denied, of those that launched with deep space plans, the total count was three, Lucy first, and then to DART and last, JWST. [inaudible 00:57:25] JWST it's like, yeah. Great minds, huh?

Bruce Betts: Yeah. I've got a new... After all this time. I believe this is a new style of trivia question. It sounds really complicated, but I think some of you, like you, Mat, can probably solve it in your head. We're doing math. That's right. We're doing a math problem. First of all, all of the following things I will mention are about telescope primary mirrors, primary mirrors. So here's your math problem? What is the sum of the number of hexagons of one Keck 10-meter telescope divided by the number of JWST hexagons, plus the Palomar Hale Telescope diameter divided by the Mount Wilson Hooker Telescope diameter.

Mat Kaplan: Oh my God.

Bruce Betts: Go to to get your numerical answer to that math problem to us. And let me toy with your emotions and your mathematical brain.

Mat Kaplan: Oh, he's put a hex on us people. And if you got lost in there, remember that you can see it on the contest page that Bruce just gave you, It will be restated for you there.

Bruce Betts: Let me give you the quick summary. It's Keck hexagons divided by JWST hexagons plus Palomar Hale divided by Mount Wilson Hooker Telescope diameters. See, it's simple. And make sure you follow standard mathematical order of operations.

Mat Kaplan: Ah, see, I was going to... You didn't mention any parentheses, so yeah. Okay. I'm glad you added that.

Bruce Betts: Okay. Just making sure.

Mat Kaplan: You got until the 19th, that'd be January 19th at 8:00 AM. Pacific Time to get us the answer to this one, get out your calculators, everybody, and our winner will get... And this is such a great way to celebrate the successful deployment of JWST. We're going to send you a tie, a beautiful gold on black tie from our friends at [Startoliolist 00:59:32]. I have one of their ties, I got it for our Planet Fest. It's perseverance with Ingenuity, the helicopter up on top. This one is equally pretty and handsome. We wish you luck.

Bruce Betts: Can you wear it as a scarf or a broach or a [telaductal 00:59:49]?

Mat Kaplan: A telaductal, sure. Why not? Just little origami telaductal out of that.

Bruce Betts: All right. Cool. Now that's nice. I like that. All right. Are we done?

Mat Kaplan: We're done.

Bruce Betts: All right, everybody. Go out there. Look up the night sky and think about oatmeal. Thank you and goodnight.

Mat Kaplan: Yeah. I love it. Whistle blueberries, frozen blueberries. Thank you. Now I know what I'm having for lunch. He's Bruce Betts. He is the chief scientist for The Planetary Society who joins us every week here for What's Up. One more pitch to help us out by completing the Planetary Radio listener survey at We want to know how you feel about the show and what you'd like to hear more of. Planetary Radio is produced by The Planetary Society in Pasadena, California, and it's made possible by its members. Mark Hilverda and Jason Davis are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.