Parker Solar Probe Will Make Closest-Ever Approach To Sun

On December 24, 2024, NASA’s probe will break its own record for closest approach to the sun—just 3.8 million miles away.

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• 1:06Speaker 01

  Early on the morning of Christmas Eve, we got closer to the sun than ever before.

• 1:11Speaker 02

  We have been waiting for this moment since 1958. On Christmas Eve of this year, we will be embracing a star. I'm dreaming of that moment.

• 1:21Speaker 01

  It's Tuesday, December 24th, and you're listening to Science Friday.

• 1:28Speaker 01

  I'm Sci-Fry producer Rasha Ureidi. This morning at around 6:40 a.m., NASA's Parker Solar Probe made its 20-second close approach to the sun, and it's nearest one yet. It swooped in to just under 4 million miles away from the sun's surface. We spoke with the program's project scientists last week to learn more. Here's Ira Flatow.

• 1:52Ira Flatow?

  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. Noro Wafi, the project scientist for NASA's Parker Solar Probe mission and astrophysicist at the Johns Hopkins Applied Physics Laboratory in Maryland. Dr. Wafi, welcome to Science Friday.

• 2:31Speaker 02

  Thank you for having me. It's a splendid pleasure talking to you.

• 2:34Ira 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?

• 2:53Speaker 02

  It's extremely close. If you think of it, I mean, 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 that Parker Solar Probe is flying through is extremely harsh.

• 3:36Speaker 02

  And it's done it 21 times already, but the 22nd is going to hit the closest approach ever to the Sun, and we cannot wait for it.

• 3:44Ira Flatow?

  Wow, and how fast will it be moving?

• 3:47Speaker 02

  Parker Solar Probe will be flying at 191 km 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 I was born after nineteen sixty nine 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, one ninety one kilometer per second, you will get from the earth to the moon in about half an hour.

• 4:26Ira Flatow?

  Wow. And now, now you talked about the harsh environments being so close to the sun. Why does the Parker Solar Probe not burn up? I mean, it has a it has a special heat shield. Describe how that all works.

• 4:40Speaker 02

  It took us sixty years to get this point. Scientists and engineers have been thinking about this mission since nineteen fifty eight. But obviously, we did not have the technology to fly the spacecraft safely around the 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 two thousand degrees Fahrenheit.

• 5:08Ira Flatow?

  Wow.

• 5:09Speaker 02

  About a yard behind, it's almost room temperature.

• 5:12Ira Flatow?

  One yard away?

• 5:13Speaker 02

  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 is basically carbon foam.

• 5:25Ira Flatow?

  Hmm.

• 5:26Speaker 02

  And it's it's so so efficient in heat dissipation. And it's it's like like magic, but it's it's actually not magic, it's engineering.

• 5:35Ira Flatow?

  Okay, you mentioned that it's shielding the probes. What are the probes picking up? What kind of sampling is going on here?

• 5:43Speaker 02

  We are at 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 flare and coronal mass ejections. And these explosions accelerate particles to almost the speed of light. And these these particles represent a hazard to space equipments like telecommunications satellites like GPS or to humans in space now, in particular that we are thinking to send women and and men to the 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.

• 6:25Speaker 02

  And one of them is that is that outermost layer of the of the atmosphere, that is the corona, is over 300 times hotter than the solar surface.

• 6:34Ira Flatow?

  Wow. Why is it hotter? Doesn't it seem weird that it's hotter?

• 6:37Speaker 02

  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 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 kilometers above, and all of a sudden, the temperature of the gas will jump to 2 million, 3 million degrees Fahrenheit.

• 7:09Ira Flatow?

  No kidding?

• 7:10Speaker 02

  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 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.

• 7:35Ira Flatow?

  Does that have to have to do possibly with the corona?

• 7:38Speaker 02

  Yeah, it's the corona, yeah. It's actually that same gas that is multi-million degree hot also generates the solar wind. So 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.

• 8:16Ira Flatow?

  Tell us some of those things it's rewriting.

• 8:19Speaker 02

  So one of the one of the discoveries that we we 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.

• 8:31Ira Flatow?

  Right.

• 8:32Speaker 02

  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 this 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's solar probe from Orbit One gave us the evidence

• 9:16Speaker 02

  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.

• 9:25Ira 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?

• 9:36Speaker 02

  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 of itself, forming an S shape. And there 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.

• 10:21Ira Flatow?

  Is there anything about how the sun works that we don't understand in great detail? And could Parker help us understand that?

• 10:31Speaker 02

  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, you know, we depend so much on space now. I mean, 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

• 11:10Speaker 02

  is about to produce one of these big explosions, will help us tremendously here. Because we can mitigate the effects.

• 11:18Ira Flatow?

  Yeah, because it could knock out satellites, right?

• 11:21Speaker 02

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

• 11:31Speaker 01

  After the break, looking ahead with the Parker Solar Probe.

• 11:39Ira Flatow?

  Hi, Ira here, reminding you that Science Friday has a dollar-for-dollar donation match, which means that any donation made through December 31st will be doubled. So now is the time to head over to sciencefriday.com/support and make a gift. Our 2025 programming depends on the generosity of our fans and listeners. Again, that's sciencefriday.com/support, and thanks.

• 12:07Speaker 00

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• 12:42Speaker 04

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• 13:11Ira Flatow?

  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?

• 13:22Speaker 02

  The solar cycle is another big mystery about the sun. I mean, 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 Ducados 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

• 14:07Speaker 02

  in the interior of the sun. How do they rise to create this cyclic activity that is a solar cycle?

• 14:12Ira Flatow?

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

• 14:18Speaker 02

  The sun is active all the time, except when at solar minimum, the activity is at lower levels. 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.

• 14:44Speaker 02

  And now we are actually at solar maximum. We covered with Parker Solar Probe a half of solar cycle.

• 14:51Ira Flatow?

  So was that by accident? You got there at a good time?

• 14:55Speaker 02

  No, not really, no. I mean, 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 anytime.

• 15:05Ira Flatow?

  Right.

• 15:05Speaker 02

  So, but we were so lucky to launch it at solar minimum.

• 15:10Speaker 02

  The reason for that, and by the way, I personally was asked this question. You build 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.

• 15:25Ira Flatow?

  Because?

• 15:26Speaker 02

  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.

• 15:42Ira Flatow?

  Right.

• 15:42Speaker 02

  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, back 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.

• 16:22Speaker 02

  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, they didn't really come to fruition. But back in 2006, '07, engineers at the Applied Physics Lab of Johns Hopkins came up with a new idea. Instead of using Jupiter, They said, okay, 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.

• 17:06Speaker 02

  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 orbit, 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.

• 17:36Ira Flatow?

  That's surprising to you?

• 17:38Speaker 02

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

• 17:44Ira Flatow?

  Well, then you must be sad when, what's its eventual fate going to be?

• 17:50Speaker 02

  Um, so, okay, personally, I, you know what? This mission has the potential to go way, way longer than the prime mission.

• 17:58Ira Flatow?

  Really?

• 17:59Speaker 02

  Yeah, it's, all 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 the whole, this whole solar cycle going from the maximum to the minimum, and hopefully beyond after that as well.

• 18:25Ira Flatow?

  Well, hey, look, look at the Voyagers. They've been going on for decades, right?

• 18:29Speaker 02

  Absolutely. And Voyager was built only for four years. Now it's almost, it's 47 years or so.

• 18:37Ira 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 as excited as you are?

• 18:51Speaker 02

  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 Neil Armstrong and other folks on the moon, and Armstrong was hooping 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 on the moon. On Christmas Eve of this year, we will be embracing a star, which is, I mean, I'm dreaming of that moment.

• 19:35Ira 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 time to be with us today.

• 19:47Speaker 02

  Thank you so much. It's really a pleasure to talk to you, Ira.

• 19:50Ira Flatow?

  Dr. Noro Wafi is the project scientist for NASA's Parker Solar Probe Mission and astrophysicist at the Johns Hopkins Applied Physics Laboratory in Maryland.

• 20:03Speaker 01

  On tomorrow's episode, dinosaurs with a side of eggnog. Lots of folks helped make this show happen, including

• 20:10Speaker 06

  Sandy Roberts. George Harper. Annie Nero.

• 20:13Speaker 02

  Jason Rosenberg.

• 20:15Speaker 01

  I'm Rasha Aridi. Catch you tomorrow.