IRA FLATOW: This is Science Friday. I’m Ira Flatow.

There’s a treat coming up on December 24th. NASA’s Parker Solar Probe will make the closest approach to the sun ever. Now Parker has made more than 20 close approaches to the sun before, yes, but this one will swoop even closer to just about a bit under 4 million miles from the surface of the sun. That is really close. And since the probe was launched back in 2018, it has helped scientists to better understand our closest star, solve some of its mysteries about solar wind, high energy solar particles, the corona, and lots more. And now scientists hope that this up close and personal view will reveal even more about the energy source we all depend on for our existence.

Here to discuss is Dr. Nour Rawafi, the project scientist for NASA’s Parker Solar Probe mission and astrophysicist at the Johns Hopkins Applied Physics Laboratory in Maryland. Dr. Rawafi, welcome to Science Friday.

NOUR RAWAFI: Thank you for having me. It’s really a pleasure talking to you.

IRA FLATOW: Oh, it’s our pleasure. Let’s talk about the Parker Solar Probe. I know that on December 24th, it’s going to set a record for the closest approach to the sun ever, and we’re talking just 3.8 million miles. And given that the Earth is 93 million miles away, this is pretty darn close, is it not?

NOUR RAWAFI: It’s extremely close. If you think of it, it’s only 4% of the sun-Earth distance, which is very, very close. And the fascinating thing for people who saw the eclipse on April 8th of this year. Parker Solar Probe will be flying through the structures we saw during that eclipse.

So it’s so fascinating to be so close to a star because our sun, the star, is the biggest object in the whole solar system. By itself, it weighs more than 99.8% of the total mass of the solar system, and it drives almost everything. The other thing, too, that environment the Parker Solar Probe is flying through is extremely harsh. And it’s done at 21 times already, but the 22nd is going to hit the closest approach ever to the sun. And we cannot wait for it.

IRA FLATOW: Wow and how fast will it be moving?

NOUR RAWAFI: Parker Solar Probe will be flying at 191 kilometers per second, and there again it’s a big number. Here on Earth, if you are flying from Philadelphia to DC, you will do it in about one second.

But let me say this. I was born after 1969 when we landed Neil Armstrong and company on the moon. I’m dreaming to see women and men back to the moon again, that I can see it live. And it will take them about three to four days to get there.

But if you pick a ride on Parker Solar Probe at that speed, 191 kilometers per second, you will get from the Earth to the moon in about half an hour.

IRA FLATOW: Wow. And now talked about the harsh environments being so close to the sun. Why does the Parker Solar Probe not burn up? It has a special heat shield. Describe how that all works.

NOUR RAWAFI: It took us 60 years to get to this point. Scientists and engineers have been thinking about this mission since 1958, but obviously we did not have the technology to fly the spacecraft safely around the sun. And to do it, you need a heat shield to protect it from the excessive heat that is coming from the sun.

When Parker Solar Probe is its closest approach, the heat shield side that is facing the sun will be glowing at about 2,000 degrees Fahrenheit.

IRA FLATOW: Wow.

NOUR RAWAFI: About a yard behind, it’s almost room temperature.

IRA FLATOW: One yard away?

NOUR RAWAFI: Yeah. And that’s where the body of the spacecraft and most of the instruments resides. They reside in the shadow cone of the heat shield. So this heat shield is basically carbon foam. And it’s so efficient in heat dissipation. And it’s like magic, but it’s actually not magic. It’s engineering.

IRA FLATOW: You mentioned that it’s shielding the probes. What are the probes picking up? What kind of sampling is going on here?

NOUR RAWAFI: We’re out of the solar maximum now. And the sun is extremely active now. And every now and then, we see this big explosion on the sun like flares and coronal mass ejections, and these explosions accelerate particles to almost the speed of light. And these particles represent a hazard to space equipments like telecommunication satellites like GPS or to humans in space. Now in particular that we are thinking to send women and men to the moon and hopefully soon to Mars as well, we need to protect them from this radiation.

But add to that that the solar corona that we saw during the total solar eclipse has a lot of other mysteries as well. And one of them is that outermost layer of the atmosphere– that is the corona– is over 300 times hotter than the solar surface.

IRA FLATOW: Wow. Why is that hotter? Doesn’t that seem weird that it’s hotter?

NOUR RAWAFI: It’s weird. If you think of it from everyday experience, if you have a heat source, the further you move away from it, it should cool down. But obviously that does not work for the solar corona. And get this, the rise of the temperature is not gradual. It’s sudden.

So we have the photosphere that is the surface of the sun that we see with the naked eye. It’s at about 10,000 degrees Fahrenheit. You move about 3,000 above, and all of a sudden the temperature of the gas will jump to 2 million, 3 million degrees Fahrenheit.

IRA FLATOW: No kidding. Rawafi

NOUR RAWAFI: Which is fascinating. And obviously you have this boiling gas that is multi-million degree hot. You cannot keep it static. So there is a flow that rises from it to fill the whole heliosphere that we call the solar wind. And the mystery about the solar wind that the particles get accelerated to hundreds of kilometers per second over a very short distance, and we don’t understand where they got the energy from.

IRA FLATOW: That have to do possibly with the corona?

NOUR RAWAFI: Yeah, it’s the corona, yeah. It’s actually that same gas that is multi-million degree hot also generates the solar wind. So Parker– when we built Parker Solar Probe, we have these three big phenomena in mind.

But Parker Solar Probe is way, way more than that. We are flying through a region of space that we never visited before. And every observation is a potential discovery, and that is exactly what we are learning from the data that– the abundance of data that Parker Solar Probe returned to us. We are discovering other phenomena about the sun, about Venus, about dust, about comets that Parker Solar Probe basically is rewriting the books about the sun.

IRA FLATOW: Tell us some of those things it’s rewriting.

NOUR RAWAFI: So one of the discoveries that we’ve made from orbit one– and actually when we launched Parker Solar Probe, we thought, yeah, probably toward the end of the mission, we will get some insights into this.

IRA FLATOW: Right.

NOUR RAWAFI: And it has– it’s also a historical discovery as well. Back in 1929, a scientist, a physicist called Henry Russell was studying dust around stars, and he came to a conclusion that there should be a region around the star that should be totally devoid of dust. And the reason for it is that when dust particles that are micron size get very close to the star, they get so hot they sublimate and they are pushed out by the radiation pressure.

The obvious place to look for these dust free zone is the sun. And since that time, people looked for it over and over and over again, but they couldn’t find a firm evidence for it. Parker Solar Probe from orbit one gave us the evidence that the dust free zone exists around the sun. That’s actually not only a discovery about the sun. It’s a discovery for billions and billions of stars out there in the universe.

IRA FLATOW: So Parker helped confirm this old theory about a dust free zone around the sun. What about the magnetic field? Has Parker taught you anything about that?

NOUR RAWAFI: Again, from orbit one and the following orbits, we observed these kinks in the magnetic field that we call switchbacks. So basically the magnetic field will roll over itself forming an S shape. And they are like gazillions of them when you get close to the sun, so many of them.

And obviously they are– they carry a lot of energy with them, and trying to explain what heats and accelerates the plasma, we are basically looking at energy sources. And these switchbacks could be one of them. When we saw them, we said, yeah, this could be one of them. So now trying to understand where do they come from, how do they form, and how do they evolve, we are actually getting closer and closer to understand the heating and the acceleration of the solar wind, which is fascinating.

IRA FLATOW: Is there anything about how the sun works that we don’t understand in great detail, and could the Parker help us understand that?

NOUR RAWAFI: Yeah, absolutely. When we talk about the solar activity, the flares, and coronal mass ejections, that’s actually one of the big phenomena out there. By the way, it’s not only our sun. Other stars in the universe do it as well.

So if we can explain that, if we can understand that and try to predict it, that will help us tremendously here on Earth and up there in space as well because we depend so much on space now. Our internets, we get it from space. Our economy in the future will be driven from space, and this activity affects us so much. So coming to an understanding when the sun is about to produce one of this big explosions will help us tremendously here because we can mitigate their effects.

IRA FLATOW: Yeah, because it could knock out satellites.

NOUR RAWAFI: Absolutely, it does. And one of the prime examples is the 40 satellites of space, SpaceX, that were knocked out about two years ago.

IRA FLATOW: Wow. Let’s talk about something I found very interesting that you said, and that is that the sun is in a really active period called the solar maximum. How does that happen, and what’s exciting about that to you?

NOUR RAWAFI: The solar cycle is another big mystery about the sun. We know about it for hundreds of years now, but we don’t really understand how the sun produces this cyclic activity that we see on the surface in the corona as well Parker Solar Probe will address some aspects of that. We’ll address the activity of it, but to understand the solar cycle itself, we need other missions that hopefully NASA will build in the future and help us understand them.

And by the way, the decadal survey that came out just two weeks ago recommended one of these missions that will fly above the poles of the sun to help us understand how the magnetic fields in the plasma behaves there, and that will give us insights at the– how the magnetic fields are created in the interior of the sun. How do they rise to create this cyclic activity that is the solar cycle?

IRA FLATOW: When the sun is at a solar minimum, when it’s not very active, does that affect the weather here on Earth also?

NOUR RAWAFI: The sun is active all the time except when at solar minimum, the activity is at a lower level. But every now and then, the sun can produce a big explosion whenever it wants. As I say, the sun will do what the sun wants to do at any time.

So, yeah, by the way, we actually launched Parker Solar Probe in August 2018 when the sun was very, very quiet. And now we are actually at solar maximum. We covered with Parker Solar Probe a half of solar cycle.

IRA FLATOW: So is that by accident you got there at a good time, or was it–

NOUR RAWAFI: No, no, no, not really. No. For a mission like Parker Solar Probe, you tell any scientist out there or an engineer out there, as long as we can get the mission, you launch it any time.

IRA FLATOW: Right.

NOUR RAWAFI: So but we were so lucky to launch it at solar minimum. The reason for that– and by the way, I personally was asked this question.

You are– you built this big mission. You invested so much into it. Why do you launch it when the sun is quiet? And my answer, that’s probably the perfect time to launch this mission.

IRA FLATOW: Because?

NOUR RAWAFI: Because the sun by nature is a very complex object, and the complexity is even higher when we are at solar maximum. So ideally to understand this complex medium, we want to start with the simplest state possible.

IRA FLATOW: Right.

NOUR RAWAFI: That is the solar minimum. And then you build the knowledge as you rise through the– as the activity rises toward the maximum. And that’s exactly what we did with Parker Solar Probe.

IRA FLATOW: This is Science Friday from WNYC Studios.

In case you’re just joining us, we’re talking about the sun with NASA’s Parker Solar Probe project scientist doctor Nour Rawafi about NASA’s upcoming flyby of the sun. Now I know that the probe had a few flybys of Venus as well. Why was that part of the mission?

NOUR RAWAFI: Venus is a key aspect of the mission. So historically when people were thinking about a Solar Probe, they were always thinking about Jupiter. We fly the spacecraft out to Jupiter, get a gravity assist, and then have a deep dive into the solar atmosphere. But those type of missions will basically result in one or two flybys, and they are very limited in time. Basically you get maybe a day worth of data when you are close to the sun, very close to the sun.

But that mission is so complex and so challenging. It’s costly as well, and NASA tried I think four or five times to do it that way. And all of them didn’t really come to fruition.

But back in 2006, 7, engineers at the applied physics lab of Johns Hopkins came up with a new idea. Instead of using Jupiter, they said if we can use Venus multiple times, we can actually get gradually closer and closer to the sun. Every time we fly by Venus, we slow the spacecraft a tiny bit down, and then it will dive closer to the sun.

And the nice thing about this aspect, first of all, the mission is feasible, it’s more cost effective, and instead of one or two flybys that are basically each one of them will provide about one day worth of data, we will have seven years for the prime mission alone. And Parker Solar Probe, now we are flying it around the sun for we completed 21 orbits by the way, and we are very close to the sun for the 22nd orbit. Parker Solar Probe has been flying through this extremely harsh environment, but it’s doing so well. And that is really surprising to us.

IRA FLATOW: That’s surprising to you.

NOUR RAWAFI: It’s amazing. When you look at all the subsystems, they are doing then better than we thought.

IRA FLATOW: Wow. Then you must be sad when– what’s its eventual fate going to be?

NOUR RAWAFI: I’m– so personally, I’m you know what. This mission has the potential to go way, way longer than the prime mission.

IRA FLATOW: Really?

NOUR RAWAFI: Yeah. It’s– all the subsystem are doing way better than we thought. So it’s basically like we launched it yesterday, which is fascinating. So after the prime mission, it is really a NASA decision to extend the mission. But the hope for us that the mission will continue to cover this whole solar cycle, going from the maximum to the minimum and hopefully beyond after that as well.

IRA FLATOW: Well, hey, look, look at the Voyagers. They’ve been going on for decades. Right?

NOUR RAWAFI: Absolutely. And the Voyager was built only for four years. Now It’s almost– it’s 47 years or so.

IRA FLATOW: December 24th, the day of the flyby is coming up. I hear the excitement in your voice. It sounds incredible. Is everybody at NASA and Johns Hopkins is excited as you are?

NOUR RAWAFI: I think everybody is excited about this. We have been waiting for this moment since 1958. And let me put it a little bit in historical context as well. And in 1969, when we landed the– Neil Armstrong and other folks on the moon and Armstrong was hopping on the moon saying his famous quote, this is a small step for man, a huge leap for mankind, I was not born back then. But still when I see it, it’s actually– I feel like I’m seeing it live.

Back then, we landed humans in the moon. On Christmas Eve of this year, we will be embracing a star, which is I’m dreaming of that moment.

IRA FLATOW: Well, I’m wishing all the best for your project for the Parker probe and everybody else who’s been working on it for so long. And good luck. And I want to thank you very much for taking the time to be with us today.

NOUR RAWAFI: Thank you so much. It’s really a pleasure to talk to you, Ira.

IRA FLATOW: Dr. Nour Rawafi is the project scientist for NASA’s Parker Solar Probe mission and astrophysicist at the Johns Hopkins Applied Physics Laboratory in Maryland.

Copyright © 2024 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/