The Sun. It’s that ongoing thermonuclear explosion that’s happening right over there. Although the Sun is necessary for life on Earth, we still have questions. So NASA has sent the Parker Solar Probe to visit the Sun, up close to get some questions answered.
Transcript
Human transcription provided by GMR Transcription
Fraser Cain:
Astronomy Cast, Episode 727, “The Parker Solar Probe.” Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos. We help you to understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the Director of CosmoQuest. Hey, Pamela. How you doing?
Dr. Pamela Gay:
I – I am doing well. Um, I’m really hoping we don’t head into a government shutdown. I am really hope –
Fraser Cain:
Again?
Dr. Pamela Gay:
Yeah. We’re heading into that again.
Fraser Cain:
Is this a thing again? Okay.
Dr. Pamela Gay:
Yeah, yeah. I’m really hoping that Hera and – and Europa Clipper make it off the ground next month. And, uh, yeah. There’s so much going on. And – and the next month, we’re gonna have so much stuff to share out. And I just wanna say, if you’re not subscribed to Escape Velocity Space News, which I put out, and you’re not subscribed to all the things that Fraser puts out through Universe Today and on his Fraser Cain YouTube channel, you are going to be missing a ton of news.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
So, go subscribe to both.
Fraser Cain:
Yeah, of expected and unexpected news that is coming down the pike.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
The sun. It’s that ongoing thermonuclear explosion that’s happening right over there. And although the sun is necessary for life on earth, we still have questions. So, NASA has sent the Parker Solar Probe to visit the sun up close to get us some answers. The Parker Solar Probe –
Dr. Pamela Gay:
Yes?
Fraser Cain:
– is one of like several spacecraft and ground-based observatories. The sun is really getting the business now. We’re really focusing our efforts on – on the sun. Um –
Dr. Pamela Gay:
Well, there’s this little thing called solar max coming up –
Fraser Cain:
Yeah.
Dr. Pamela Gay:
– and it turned out a whole bunch of nations simultaneously got the realization, “We should be watching this. We should see what happens.”
Fraser Cain:
Yeah, yeah. Exactly.
Dr. Pamela Gay:
And so, they’re doing the thing.
Fraser Cain:
Yeah. Um, so, let’s talk about the Parker Solar Probe then. What is this spacecraft designed to do?
Dr. Pamela Gay:
Its primary mission is to go into the sun’s outer corona and try and understand why it’s so hot from super up close. It’s looking to measure the position, and it has succeeded in doing this, where the sun stops being the sun and starts being the solar wind. So, there’s this place where particles stop being directly connected to the sun through gravity and electromagnetic forces and actually fly free and out into space to cause beautiful things like the solar aurora that you’ll probably be able to see tonight where you are in Canada. And I’m very jealous, by the way.
Fraser Cain:
Yeah. We got a couple of announcements, yeah. And we’ve got clear skies. We didn’t have clear skies for the last couple of days, but we have clear skies tonight and probably for the next three or four nights. So, um, yeah. I mean, this mystery – this is one of the greatest mysteries –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– in solar astronomy is that if you measure the surface of the sun, it is, what, 5800 Kelvin.
Dr. Pamela Gay:
Mm-hmm.
Fraser Cain:
And then if you just go out into space several hundred thousand kilometers off the surface of the sun, the temperatures rise to millions of degrees.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
And that’s weird, right? That hot gas that’s in this sort of outer atmosphere around the sun is millions of degrees hotter than the surface. How is that possible?
Dr. Pamela Gay:
Well, according to the second law of thermodynamics, it is not.
Fraser Cain:
Yeah, okay.
Dr. Pamela Gay:
Heat should not flow from the cold place to the hot place. This is, just to give you a sense of what’s going on, like imagining a scenario where your lightbulb is able to heat that hamburger what – in whatever cheesy grill you’ve gone to, to a temperature hotter than the surface of the glass on the lightbulb.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
That hamburger does not exist. And – and so, –
Fraser Cain:
Yes.
Dr. Pamela Gay:
– to explain what’s going on, we have to look for some other means. Some force that is moving stuff, that is able to release energy, and it’s that release of energy from something that must be doing the super heating.
Fraser Cain:
Yep. So, the Parker Solar Probe was designed and built to try to answer this and other questions in the solar environment. Now, being close to the sun sounds dangerous.
Dr. Pamela Gay:
It just might be. In fact, this – this mission has a, uh, four and a half inch carbon foam core in its heat shield with two panels of reinforced carbon carbon composite on either side of that shield –
Fraser Cain:
Wow.
Dr. Pamela Gay:
– that is used to – to basically, uh, shield the mission every time it gets close to the sun. And one of the things it does that absolutely floors me is the mission has two different solar panel setups. And it uses the small one when it’s getting super close to the sun, and it actually has to pull in its other one to keep it out of the sunlight because the sun is too powerful –
Fraser Cain:
Right.
Dr. Pamela Gay:
– for the solar panel.
Fraser Cain:
Wow. It’s like, I don’t know, sunglasses. I’m not sure. But, yeah. So, it has a small set with close to –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– just deal with the intense light. And then when it’s far enough away, it can then deploy its – its bigger panels. Uh, but even they are very small. When we think about, say, Europa Clipper that has solar panels that are 20, what, 33 meters long. They are the size of like a football field and the Parker Solar Probe is so close it doesn’t need a lot of solar panels. In fact, cooling is part of the issue. And so, this – this trajectory that the Parker Solar Probe takes around the sun, this is special as well.
Dr. Pamela Gay:
Yes. So, the mission launched in 2018, and it has made multiple rendezvous with the planet Venus. And it keeps changing its orbit to keep it essentially in a low-key resonance with Venus. So, it keeps re-countering the planet. And with each encounter with Venus, it gets a kick that allows it to get closer to the sun as it goes around and shortens its orbit. So, in November, it’s going to be making its closest approach to Venus. It’s going to reach just 317 kilometers from the surface of Venus –
Fraser Cain:
Wow.
Dr. Pamela Gay:
– which is its other science target. It’s – it’s absolutely amazing and it’s going to allow it to drop into an orbit that is just 6.9 million miles from the surface of the sun. It’s gonna be on an 88-day period. And with every orbit, it is setting new fastest human moving object –
Fraser Cain:
Right.
Dr. Pamela Gay:
– in the solar system records. And, um, so – so the next approach is going to be right after this episode comes out. So, September 30th, it’s – it’s going to be making its last approach on the current orbit. Then November 6th, it does this amazing fly-by of Venus. And then it’s on its final five trips around the sun in its primary mission. There’s no reason to think it won’t get extended.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
Um, but what I’m kinda loving is its final planned approach is on my birthday in 2025 on December 12th.
Fraser Cain:
Oh, that’s really cool. Right. And so, it’s kind of amazing to me, you know, like, this is just time accelerating that, as you say, it’s been since 2018 it’s done a ton of fly-bys, getting closer and closer already. And really, it just has a handful left until it reaches the end of its primary mission. But as you said, it can last for a long time, and we should not anticipate that the prime – like it’s gonna just screech to a halt at the end of the primary mission. It’s gonna keep on going. As long as it’s still in good condition, we’ll get a lot more science out of it.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
So, let’s talk about the science. So, what has Parker Solar Probe helped us understand about that big mystery that we talked about at the beginning of the episode? And just like other mysteries in general.
Dr. Pamela Gay:
So, the – the Parker Solar Probe is named after Eugene Parker, who we’re gonna be talking about in detail in our next episode. And he is someone who postulated that non flares are what are transferring energy into the solar corona. Uh, since then, we’ve also seen discussions of Alfven waves, uh, and this is one of those episodes where I have to say I have read more solar science than I have listened to. So, please be gentle if I’m mispronouncing –
Fraser Cain:
Right.
Dr. Pamela Gay:
– this word of many scary letters combined. Um, so – so, Parker Solar Probe has also looked at Alfven waves and it has found the – what’s called the Alfven surface of the sun, which is the point where, uh, energy being transmitted stops being associated with the sun and able to transfer back to the surface of the sun, and instead, is part of the solar wind at that point. It was projected to be somewhere between, uh, 10 and 20, uh, solar radii away from the surface. They found it at 18.8. It’s always great when things we think are true actually turn out to work –
Fraser Cain:
Yeah.
Dr. Pamela Gay:
– with the sun, which we are so wrong about so often.
Fraser Cain:
And you mentioned nanoflares. So, what are nanoflares?
Dr. Pamela Gay:
So, nanoflares are small points where – I mean, I’m holding my hand up as though that were realistic. So – so, we’re used to seeing these massive flares that you can actually see in a four inch telescope in your backyard.
Fraser Cain:
With an appropriate solar filter.
Dr. Pamela Gay:
With an appropriate solar filter or projected onto a piece of paper. Pick one.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
With – with nanoflares, you really need a spacecraft to be able to see them. They were able to see them with Parker Solar Probe. And these are smaller places where magnetic field lines are reconnecting and releasing energy when they do this. So, the question becomes in what way are solar waves – are waves propagating through solar magnetic fields able to release said energy into the solar corona? This is really what it’s coming down to.
Fraser Cain:
Right.
Dr. Pamela Gay:
Alfven waves are where you have a magnetic field line that, for whatever reason, gets a wave propagating and it’s a standing wave. So, it’s moving in mass down the – the magnetic field line. As it propagates down, it’s carrying energy with it, and it has the ability to release that energy into the outskirts.
Fraser Cain:
Right.
Dr. Pamela Gay:
Nanoflares are reconnections of field lines. All these different things, we’re trying to figure out what is the dominant way of releasing energy out into the solar corona that allows an energy to not be heating lower levels.
Fraser Cain:
Right, right.
Dr. Pamela Gay:
Um, yeah.
Fraser Cain:
And it is, like – does it end up being one or the other? Is it really something like a mix of these various features on the surface of the sun that are contributing to this coronal heating?
Dr. Pamela Gay:
We’re still trying to figure out what the dominant cause is, but we do know it’s a multi-pronged answer. It’s expected that there’s gonna be one thing that is like the most big reason for this happening, the largest cause behind this heating. But what’s interesting is, like, Parker isn’t just finding things that – that we knew should exist, which is magnificent, that is so awesome for all the scientists whose work is getting proven true. It’s also out there going, “Nope, this doesn’t work.” So – so, one of the things that – that Parker Solar Probe discovered in its very first pass was there are switchbacks in the magnetic field lines of the sun where – where the lines literally coil back on themselves, making “S” shapes.
Fraser Cain:
Wow.
Dr. Pamela Gay:
And – and so, Parker’s flying through and it’s able to detect all these wild switchbacks in the magnetic field. And there was this moment in time of how – how do these form? How does this work? And are they what’s carrying this energy out? Well, it’s been figured out that the way they appear to form is you have magnetic field lines that are rising up from the convection cells in the sun, and as those convection cells are doing their thing, motions in the convection cell can essentially whip these lines around, creating these switchbacks in the magnetic fields. But it appears as if a paper back in July 2024 that there’s not enough energy in these switchbacks to be what’s heating the corona.
So, we have this super cool thing. It was super promising for a hot minute and then, uh, it turned out that heat was insufficient to heat the solar corona.
Fraser Cain:
Right, right. It – it’s amazing that the sun is as complicated as it is. I mean, when you really just think about it. It is a blob of –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– hydrogen and helium, with a few other metals mixed it, but they are a fraction of the hydrogen and the helium. It’s held together by the mutual gravity of all of the stuff –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– that’s there. And yet, you get layers with the core and the radiative zone and the convective zone. You get blobs of material rising and falling like a lava lamp. You get these magnetic fields that get twisted up and switch places. Polarity every 11 years.
Dr. Pamela Gay:
Mm-hmm.
Fraser Cain:
You get these nanoflares on the surface. You get the – the granules, which are the points where the convective blobs are rising up. These magnetic field lines twist and turn. You get sunspots, which are areas of relative cooler where the – the field lines are breaking through –
Dr. Pamela Gay:
Radiating out.
Fraser Cain:
– the surface of the sun. And then these things are – are combining with waves passing, propagating, down the magnetic field lines that are bunching up and heating up material in the – in the solar atmosphere. And then this material is being driven energetically at, in some cases, hundreds of kilometers per second, out into the solar system where it interacts and creates this bubble around the solar system. And it’s not like there’s external random inputs that are going into this. I mean, when you think about, I don’t know, just like most stuff – like even orbits. Like say, orbits of the moon around the earth. Like, the tides come because of this – this weird interaction –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– the gravitational interaction between the earth and the moon. And if the moon didn’t exist, then we wouldn’t have tides. And if we had a bigger moon or the moon was closer, we’d have different tides. And the ground would be heaving. And if it got too close, it would break up. Like, all these interactions. But the sun is just a blob. Just sitting there doing its thing.
Dr. Pamela Gay:
Yep.
Fraser Cain:
And yet, it leads to all of this complicated emergent process that has baffled astronomers for a century.
Dr. Pamela Gay:
And we keep finding new ways that it’s complicated. So, like, the Voyager probes have finally both made it passed the heliopause. They have left –
Fraser Cain:
Yeah.
Dr. Pamela Gay:
– that outer bubble. But then Parker Solar Probe discovered a new inner bubble where the first 3.5 million miles, or 5.6 million kilometers, from the sun is a no dust zone because the sun – it – its radiative powers have blasted out of existence any dust that tried to exist in that inner layer. So, now we know that there’s this inner sphere that is dust free, thanks to the – the sun’s heat and power. We know that there’s the – the inner parts of our solar system that are safe from a whole lot of cosmic rays that would otherwise be bombarding us. And so, we just keep encountering these different transition zones and what the sun is able to do is it influences its environment.
Fraser Cain:
Yeah. So, what has Parker taught us about Venus?
Dr. Pamela Gay:
That it can actually be seen from outer space. Like, its surface can be seen from outer space. This was one of those things that was like, “How? That can’t be possible. What are you talking about?” when I read about it. It turns out the surface of Venus is so hot that it radiates light in the furthest red of visual and the nearest infrared light. And the Parker Solar Probe has, on multiple passes now, used its wild field camera to observe the nighttime side of Venus. And it can make out the – the geology of the surface and what temperatures are being radiated –
Fraser Cain:
Wow.
Dr. Pamela Gay:
– and – and the geography of the surface by being able to make out where the plateaus and the planes are. And what’s amazing is seeing these visual light nighttime because the planet is glowing images side by side with – with the Magellan radar images. And it’s like, “Oh, I can match these up. I am actually looking through the clouds.”
Fraser Cain:
Yeah.
Dr. Pamela Gay:
It’s – it’s a hot world. It’s a very, very hot world.
Fraser Cain:
It is amazing. When we think about the images of Venus, we’re very familiar with that orange ball picture –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– that has been – and that was taken by the Magellan spacecraft but –
Dr. Pamela Gay:
It was radar.
Fraser Cain:
With radar, right. And so, that’s not, like, the real color. The spacecraft was equipped with a – with a – with a radar system. It was sending pulses down. Watching as the pulses bounced off the surface of the, you know, and back up to the spacecraft. And it detected the distances, and they were able to measure, with pretty low resolution, the surface features.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Like, I think they’re down to like a kilometer –
Dr. Pamela Gay:
Yeah. That’s – that’s about right.
Fraser Cain:
– per pace or something.
Dr. Pamela Gay:
It depends on where the surface it is.
Fraser Cain:
Yeah, yeah. And so, they don’t know a lot about the surface of Venus. And that’s it, as you said. No other – we can’t detect the surface from Earth. We can’t detect the surface with the various – Mariner spacecraft, the – all of the – the Venera probes that fail – like, only when they got down to the surface could they actually see the surface. Until then, it had been this mystery. It wasn’t until Magellan told us that a surface even existed at any, you know, at any kind of resolution.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
And yet, here his Parker Solar Probe, with this not being its primary objective, passing by and going, “Oh, look. I can see mountains. Moving on.”
Dr. Pamela Gay:
To be fair, most missions that were flybys were like, “We should look at the daytime side.” And that was their mistake.
Fraser Cain:
Right.
Dr. Pamela Gay:
It turns out you need to be looking at the nighttime side.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
It’s – it’s just one of those things that is – is truly flooring. And of course, it’s looked at Venus’ plasma tail and helped us map out the plasma tail. And one of my other – to switch topics to another planetary object, one of my other favorite results is Parker Solar Probe has on board equipment to measure electrons, protons, and alpha particles, helium ions. It has on board dust detectors. And – and because it can detect all these different particles, they used it to try and figure out the cause of the Geminid meteor shower. And – and this meteor shower, which occurs every December, again when my birthday is –
Fraser Cain:
Yeah, and it’s the best one.
Dr. Pamela Gay:
It’s the best one.
Fraser Cain:
Yep.
Dr. Pamela Gay:
And – and it’s caused by an asteroid, which is not what is supposed to cause meteor showers. The question has always been is – is this asteroid actually just a dead comet core that’s on an inner solar system orbit somehow? And by looking at the kinds of particles and the speeds of the particles involved, they were able to compare several different models to figure out what kind of activity would have jettisoned those particles, creating the observed meteor shower. And they figured out something violent happened to the asteroid. It wasn’t just like a comet outburst. It was an asteroid got it probably by something else. Probably a smaller asteroid. And that collision, that violence, is what generated the particles that cause every December the Geminid meteor shower.
Fraser Cain:
That’s really cool.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Um, so, how is the spacecraft doing? I mean, I think –
Dr. Pamela Gay:
It’s fine.
Fraser Cain:
It’s fine. Near the sun. Like, flying through the –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– upper atmosphere of the sun. And how’s it doing? It’s good, you know?
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Nothing weird. Nothing – no big disasters have happened.
Dr. Pamela Gay:
My only concern for the mission is the current NASA budget because there – there is currently a lack of funding and a mandate to go to the moon. And the Artemis Program is the great vacuum in the administration at the moment. But as – as long as they can keep going. The latest National Academy study that came out last week really gives me some hope because it called out NASA for, uh, apparently 83% of NASA’s infrastructure has outlived its predicted lifetime, and at some point, that will catch up to NASA.
Fraser Cain:
Right.
Dr. Pamela Gay:
Um, so – so, there was a call to look to the future, to plan for the future. So, I am hoping that part of that plan will include, “Let’s keep LRO going as long as we can. Let’s keep MRO going as long as we can. And let’s keep missions like Parker Solar Probe, solar dynamic orbiter Soho. Looking at the sun, helping us stay safe, and working with us to understand solar weather.”
Fraser Cain:
Yeah. it is kind of ironic that –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– NASA overbuilds and does such a good job, a careful job, with the missions that it builds that they last a lot longer than the original mission was intended. And so, that requires ongoing maintenance and teams to communicate and time on the deep space network and – and we saw, for example, that they’re shutting down Challenger, not because it’s failing but just because –
Dr. Pamela Gay:
Money.
Fraser Cain:
– they don’t have the maintenance budget to be able to maintain the spacecraft. Uh, that’s bonkers.
Dr. Pamela Gay:
And Hubble’s looking at some major cuts and so the question becomes what does Congress allow to happen though? This is the other thing that everyone’s keeping an eye on. Because while NASA an express their desires to cancel programs, a mission’s not over until Congress deallocates its funds.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
And so, right now there’s notes coming from congressional committees that just might provide the grace needed to keep Viper going and to keep Chandra and Hubble going. Chandra was given a brief reprieve. We get to see how long it keeps that reprieve.
Fraser Cain:
Do we know what the final stage for Parker will be? I mean, I love the idea of them continuing to test out its resilience. Like, maybe when they’re – when they’re finally right at the end, they go, “Well, let’s see how close to the sun we can get before we die.”
Dr. Pamela Gay:
So, it would have to have additional Venus encounters. Uh, get those more gravitational assists to get it out of its current 88-day orbit. Um, that’s not impossible. I don’t know what mission planners have done that is the unofficial, at this point, future of the mission should it be granted a continuing chance. Um, but, yeah. In order to get any closer to the sun, it will need to meet up with its good friend, Venus.
Fraser Cain:
Yeah, right, right. But the, you know, with a couple more flybys, who knows how close we could get. I mean, couple of million kilometers above the s – I would love just as – you know, we saw the end of Galileo going into Jupiter. We saw the end of Casino going into Saturn. And I would love to see the end of – of Parker going into the sun, but you know, that’s just me. It’s the hardest place to reach in the solar system.
Dr. Pamela Gay:
It really is.
Fraser Cain:
Yeah, yeah. It would show our technology.
Dr. Pamela Gay:
It’s much easier to fling your enemies out of the solar system than to fling them into the sun. Just saying.
Fraser Cain:
Yeah, yeah. Yeah, when people always say, “Oh, we should just throw our garbage into the sun.” Like, that’s the hardest place to reach in the solar system. You’re kind of like saying, “Why don’t we, you know, throw our garbage to the – throw our garbage on the tops of mountains.” It’s really hard.
Dr. Pamela Gay:
Yeah, please don’t.
Fraser Cain:
Yeah, don’t. Don’t.
Dr. Pamela Gay:
[Laughs]
Fraser Cain:
That’s Mount Everest. That’s how we got Mount Everest.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Anyway. Well, so cool. And, like, I doubt this is the last conversation we’re gonna have about the Parker Solar Probe. There is so much science to be done. So many amazing discoveries. And it is doing great. And so, hopefully we will do a follow on it in a couple years and just give you – because we are all still in this – in the middle of this time when we just don’t know all the answers about how the sun works.
Dr. Pamela Gay:
It’s true.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
And that’s – that’s one of the most amazing things is we have a star right next door, and it is still a mystery that we are learning about.
Fraser Cain:
Yeah. Thanks, Pamela.
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