Ep. 559: The Surface of the Sun

Posted on Feb 11, 2020 in Astronomy, podcast, Solar System, Stars | 0 comments


A brand new telescope has completed on Maui’s Haleakala, and it has just one job: to watch the Sun in unprecedented detail. It’s called the Daniel K. Inouye telescope, and the engineering involved to get this telescope operational are matched by the incredible resolution of its first images.

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Fraser:                         Astronomy Cast Episode 559 – The Surface of the Sun. Welcome to Astronomy Cast, a weekly facts-based journey through the cosmos where we hope you understand not only what we know, but how we know what we know. I’m Fraser Cain, 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?

Pamela:                        I – I’m doing well and I’m so pleased to say that since our last episode when we said that we’re looking for help with CosmoQuest’s Open Source Project, I’ve had a number of Astronomy Cast people show-up on CosmoQuest’s Discord and we’re pulling together a great group of humans. So, thank you all the humans out there interested in helping us with CosmoQuest.

Fraser:                         And, let’s say a person didn’t hear that first call for – for help and may still want to throw some code into the, I don’t know my analogy is falling apart here.

Pamela:                        GitHub, falling into the GitHub, yeah.

Fraser:                         Into the GitHub, yeah. Throw some code at the GitHub. How can people get involved?

Pamela:                        The – the best thing that you can do is go over to cosmoquest.org, click on the Discord link, and say, “Hi” in the volunteers reporting for duty channel. And, we will add you to our Coder’s group, add you to the GitHub repo, and off we shall fly, open-source away.

Fraser:                         That sounds great. Alright, so a brand new telescope has been completed on Maui’s Haleakala. And, it has just one job, to watch the Sun in unprecedented detail. It’s called the Daniel K. Inouye Telescope. And, the engineering involved to get this instrument operational are matched by the incredible resolution of its first images. And, I think we need to apologize in advance to everyone who is listening to this episode conveniently as a Podcast because I’m probably gonna be showing some pictures. We are gonna be talking about one of the most incredible images of the Sun that has ever been taken.

And so, I think the hope here is that the listeners are already familiar with this image and now they’re waiting for their favorite astronomy explainers to follow-up and give them some – some context to what it is. But, if you don’t, I’m sure we’ll have a link in the Show Notes. Search for Sun surface picture on Google and you will have this incredible picture. If you get hungry for Caramel Corn, you are – you are looking at the right image.

Pamela:                        And – and, if you go find it on YouTube, you’re just gonna want to stare at the Sun’s surface, with this telescope not with your eyeballs, kinda forever.

Fraser:                         Yeah, yeah. It’s so beautiful. That’s a – that’s a Bug’s Life reference. Okay, so let’s talk about this picture.

Pamela:                        Okay.

Fraser:                         Let’s talk about this telescope. Where should we start?

Pamela:                        Let’s start with the telescope.

Fraser:                         Okay.

Pamela:                        Well, it’s hard to talk about an image when you know nothing about the telescope. One of the things that we’ve brought up over and over and over on this show is you can get higher resolution images by using telescopes with a larger diameter. You can do this with interferometry. You can do this with larger collecting areas. And today, we’ve never gone too gung-ho collecting light from the surface of the Sun because the Sun is a giant, hot, boiling ball of plasma and its light can melt things.

Fraser:                         Yeah, and then when you concentrate it with a mirror as we have seen with what you do when you have a magnifying glass –

Pamela:                        Yeah.

Fraser:                         You – you turn the sunlight into a laser beam.

Pamela:                        I – I have inadvertently started fires twice with telescopes, looking at the Sun.

Fraser:                         Yeah, I have merely destroyed a telescope. Yeah.

Pamela:                        Oh, I – I’ve been very good about not destroying telescopes; it’s just the things around them I keep setting on fire.

Fraser:                         Yes. I’m not sure which one is worse. I’m gonna say that what you’ve done is worse than what I’ve done. I’ve merely destroyed a $200.00 telescope; you’ve tried to light a house on fire.

Pamela:                        A piece of paper and some carpeting, but.

Fraser:                         Yeah, that’s funny. Right, so trying to magnify the light from the Sun is madness, and yet –

Pamela:                        And yet –

Fraser:                         In order to see detailed images of the surface of the Sun, you wanna magnify the image. How can this be done? What wizardry?

Pamela:                        Very – wizardry is the correct answer. So, every single aspect of this telescope is designed to make this system as safe as possible and to prevent any excess heat. This means that the dome has a unique design. Where instead of having the normal roll-up slit that leaves this big stripe of opening into the dome, they have a circular annulus that –

Fraser:                         Right.

Pamela:                        Opens up that is matched to only let in enough sunlight to illuminate the entirety of the 4-meter mirror that’s on this telescope. So, they start by restricting how much light gets into the dome. Now –

Fraser:                         Yep. So, they – they – and, to just – before you continue on a four, I think, it’s like a what? A 4.2-meter mirror –

Pamela:                        Yeah.

Fraser:                         That’s – it’s – that’s a big mirror. I mean it’s –  

Pamela:                        And, it’s super thin, it’s 75-millimeters thick.

Fraser:                         Right.

Pamela:                        So, this is a system that they can do adaptive optics with and –

Fraser:                         Yeah.

Pamela:                        It’s also thin so that it doesn’t overheat.

Fraser:                         Right.

Pamela:                        This is one of the amazing mirrors that came out of the Mirror Lab in Arizona.

Fraser:                         Right. And so, it’s got these actuators underneath the surface of this, of the primary mirror that allow it to – to make minor distortions and – and try to compensate for the atmosphere that’s above it. So, you’ve got this – this enormous amount of light going into this – this 4-meter, 4.2-meter hole on the side of the – this observatory, bouncing off of this primary – getting focused and –

Pamela:                        Now, now I do have to step back and say that while the mirror is more than 4-meters in size, they’re only utilizing 4-meters of the mirror.

Fraser:                         Uh-huh.

Pamela:                        This – this is, a design where they’re not going all the way out to the edge when they use it.

Fraser:                         Yeah.

Pamela:                        And, they also are focusing it in a kinda crazy way which is also part of why they’re not using the entirety of the mirror. They didn’t wanna have to put anything in the path of the sunlight.

Fraser:                         Right.

Pamela:                        So, they have the light coming in through that exactly sized hole in the dome of the telescope. The sunlight goes through that hole, hits the mirror which is tilted and shaped ever so slightly to direct the light out of the side of – of the incoming light. So, the light comes in, bounces sideways –

Fraser:                         Right.

Pamela:                        Gets focused onto a secondary liquid-cooled metal donut of a system.

Fraser:                         Yes. Yeah, they call this the heat-stop.

Pamela:                        And, this incredible system eliminates 95% of the heat.

Fraser:                         Right.

Pamela:                        This –this prevents them from melting anything further down.

Fraser:                         Right. And, I think that the thing that’s really important, so a couple things there, as you were saying, right? With a traditional solar telescope you put your, the block, whatever you’re gonna use to decrease the brightness of the Sun, you put that at – in front of the main hole on the telescope.

Pamela:                        Yes.

Fraser:                         So, if you’ve got a Newtonian Telescope, you put it in front of the entire, before the light can even get inside your telescope, you’ve already shaded it.

Pamela:                        They’re not doing that.

Fraser:                         And, and – and they’re not doing that. They’re – they’re waiting. And so – and so, – the – and the reason, if I understand is that they don’t wanna have even slight problems with whatever filter they would have to put in front of it. That would decrease the quality of the image.

Pamela:                        So, their goal is to remove anything that might create contrast issues, remove anything that might create optical aberrations, remove basically, anything extra that they don’t absolutely, have to have. The light comes in; they have 95% of the light from all 44-meters of the telescope going up to this donut. So, they’re keeping the resolution and throwing out unnecessary light so they can still do all the science they want, and get maximal-resolution out of their detector.

Fraser:                         Right.

Pamela:                        Now, at this point, it starts to act more like a normal telescope. They’re shooting the light down to what’s called a coudé focus. This is where you have some sort of a split that takes the light and moves it from that room that your telescope is living in and generally shoots it to the basement somehow.

Fraser:                         Right.

Pamela:                        Lot’s of telescopes do this in different ways. The 107-inch telescope at McDonald Observatory, which I’ve used the coudé spectroscope on, it shoots it through the – the pier of the telescope, down through the floor, and into a different room using mirrors. The Hobberly Eber – Hobby-Eberly Telescope, it uses fiber optics to do this. Lots of telescopes nowadays are accomplishing this with fiber optics. They pickoff the light, move it through the cables, get it into their big basement room. Now, the reason you’re using this big basement room is so that you can have massive instruments to spread the light out to create spectra, do all sorts of amazing stuff.

And, normally you have some sort of rotational system to keep things fairly aligned, but you’re looking at stars. You’re not looking for too long and you’re not worried about rotation too much. They’re looking at the Sun, the entire day.

Fraser:                         All day long. Yeah.

Pamela:                        Yeah. And so, they do what I consider to be one of the most crazy, awesome things I have ever seen done with a coudé room. They’re rotating the whole darn room.

Fraser:                         The whole room just turns – 

Pamela:                        Yes, yes.

Fraser:                         To keep the instruments it – aligned with the – with the telescope and everything that’s bouncing around.

Pamela:                        This is a 150-ton platform of instrument –

Fraser:                         Yep.

Pamela:                        That they are precisely rotating as they track the Sun. So, their tracking isn’t just moving a 4-meter telescope. Their tracking isn’t just moving very precisely a dome. And, domes normally don’t have to move – move precisely. They have to track the dome precisely, track the telescope precisely, and track the 150-ton coudé laboratory precisely. This is remarkable engineering. I – I can’t imagine what the construction company they went to originally thought when they were asked, “Can you make this entire room track the Sun?” Yes, they could. But, probably not anything anyone expected they’d be doing when they got their mechanical engineering degrees. It’s a feat of engineering that –

Fraser:                         Yeah, it really is. One of the other feats of engineering is just temperature control.

Pamela:                        Yes.

Fraser:                         I mean, again, you’re bringing in I think it’s like 12 kilowatts of energy nonstop, continuously just bringing in enormous amounts of energy into this enclosed space. And, you have to get rid of it.

Pamela:                        Yeah. And – and, they do this through a variety of ways. They have, first of all, extra gaps, in this case, rooms between the dome floor. And then, when you get down to the instrumentation, having extra rooms, well it’s sort of like having storm windows in your house. Those air gaps provide a place where heat gets dumped and then doesn’t get transferred. And then, they are just coolant-ing everything. That donut, I’m just gonna be in awe for a while.

Fraser:                         Yeah, yeah. So, they – if you look at the outside of the – of the actual shutter, of the outside of the dome, they’ve got these – these flappy shutters –

Pamela:                        Louvers.

Fraser:                         Yeah, that are all across the outside of it. And so, they can do a lot of really, sort of high and quick, quick – very – quick response temperature control. They make ice in the observatory at night when it’s cooler on the top of this mountain and then they pump it through. They use this as a way to – to run coolant through the entire system. There’s like seven kilometers of coolant piping throughout this entire instrument. So again, and as you said, they have all this air gapping inside that – that they can then also use to – to try to – to maintain the tee.

And so, the goal is just to, that every single part of this entire telescope, from the mirror to the instruments, all the way down to the ground level, the whole thing is precisely the same temperature all the time.

Pamela:                        And – and, that is really the key. And, this is a problem that we’ve been trying to solve with telescopes for a while now. Once our telescopes got good enough, we realized air is the enemy, because if you have temperature variations in the air, each of those temperature variations will bend the light. Air can act like a lens, its super annoying. Now, with a regular everyday telescope, you open the dome, you turn on some fans, you make sure all the doors are open, and you’re good enough. But, as we’ve started building bigger and bigger telescopes, we’ve had to start figuring out how to add all of these basically, Venetian blind systems that open up and circulate all the air.

So, all day long inside these nighttime telescopes, you run air conditioning to try and keep the room at the temperature you expect the nighttime to be. Well, here they’re flipping that on its head and they’re trying to keep everything the temperature it’s going to be during the day and not have any greenhouse effect going on. So, just like our – our cars will heat up in the sunlight, domes will heat up in the sunlight.

Fraser:                         Yeah.

Pamela:                        And, that would be death to the system’s accuracy.

Fraser:                         And, you’re bringing in all that heat.

Pamela:                        And, you’re bringing in heat.

Fraser:                         Yeah.

Pamela:                        So, essentially they’re bringing in heat and they have to constantly prevent that heat from heating up the air. And, it’s not easy and they have figured it out.

Fraser:                         Yeah.

Pamela:                        And, this is where I think we should start talking about these amazing images.

Fraser:                         Let’s do that. And so, again if you – if – if you need to pause the Podcast, go get yourself in front of a browser, and take a look at the pictures that, that this – this – this incredible telescope has – has taken. And so, now assuming that you have done this or you’re kinda familiar or you’re just gonna sort of follow along with us. Tell us, and I’m gonna show the picture for the people who are watching this as the Livestream, but tell us kinda what we’re looking at.

Pamela:                        So, the – the image that the – this telescope produced is a series of hot cells that are yellowy in the center, fade-out, and then are surrounded by inky black darkness. Now, the crazy thing is that inky black darkness is still super bright. What – what we’re seeing is slight temperature variations in the surface of the Sun where convective cells of hot gas are rising-up. And then, through the center, they’re rising up and then cascading down as they give off their heat to outer space.

And, because luminosity causes temperature to the fourth power, the very small temperature variations from the center of these convective cells out to the cool edges of these convective cells, well they have amazing differences in luminosity. That, because of the limiting contrast of what we can do with images and eyeballs, we perceive as dark out – outlines around bright cells.

Fraser:                         And – and – and so, sorry, so like the bright parts that we’re seeing.

Pamela:                        Uh-huh.

Fraser:                         Those are the hottest parts, the parts where the Sun is, actually blobbing out its convective material from the interior. And then, the darker regions are still insanely hot.

Pamela:                        Yes.

Fraser:                         Just less hot than the actual bright surface.

Pamela:                        And – and, what makes these particular images so remarkable is each of these convective cells is roughly the size of France or Texas, which are remarkably about the same size, but Texas is bigger. These convective cells on the Sun are the size of France or Texas. And, we can make them out, not just as a few pixels across but as gazillion, not literally gazillions –

Fraser:                         Yeah.

Pamela:                        But, as a lot of pixels across, because this instrument can resolve features that are just 12 miles or 20 miles in – 12 miles or 20 kilometers in size.

Fraser:                         Yeah, yeah. So, the little – if you zoom in on the image and you can see individual pixels, these are on the order of 12 – as you say, like 20 kilometers across. And, when you think about the fact that we’re seeing these images from 150 million kilometers away, it’s just an incredible feat of – of engineering in astronomy to be able to do this.

Pamela:                        And, the entire field of view for this telescope is – is measured in arcseconds. This is an extremely high-resolution system. We’re never gonna get Full-disk of the Sun. Heck, there may be Sunspots that come up that are bigger than this telescope can see.

Fraser:                         Yeah.

Pamela:                        But, with this kind of resolution, even now in its engineering phase, we’re seeing things that when you try and look up information on them, current publications say, “Can’t be resolved. Not well understood. Bright things.” Faculae are what I am thinking of here, we know that there are magnetic effects that occur in those dark boundaries between individual convecgive – convective cells and these bright magnetic effects aren’t well understood. And, this may be how we finally are able to understand them. This telescope is still in the process of being commissioned. We’re talking about it now because we’re getting amazing images off of it.

And, the time is right to say, “Photosphere here we come.” The top 50 miles of the surface of the Sun is about to be ours to understand in detail.

Fraser:                         So then, what is the point? Now obviously, it’s incredible to see these high-resolution images of the Sun. But, what is it good for? How does this make my life better?

Pamela:                        Well, it’s hopefully gonna help us better understand solar weather, better be able to make predictions of what’s going on. The top layer of the Sun, while generally kind of ignored because it’s not as striking as the – the higher up layers, this – this photospheric layer, it varies from hot spot to cold spot between about 4,500 degrees and 6,000 degrees Kelvin, that’s 4,200 to 5,700 Celsius. And, the effects that occur at this level, lead into bigger and bigger effects as you go up in the Sun’s atmosphere. The faculae that we see as bright nothings at the surface of the Sun, at the photosphere, end up growing into bigger and bigger things called flages as you get higher up in the atmosphere.

These can end up forming coronal loops that in the outermost layer of the Sun, these are the big magnetic loops that we see that when they let loose can blast particles our direction, that take out communication satellites.

Fraser:                         Right. And, – and that’s like if you want the real practical advantage for observing the Sun at this level of detail, advance-warning of a solar storm that’s going to cause a serious disruption to our modern interconnected human society is – is the benefit that you enjoy, is some advance-warning. Like, right now, what do we get? Like two hours of notice that there’s a significant solar storm inbound because –

Pamela:                        Yeah.

Fraser:                         We’re starting to detect the first particles smashing into the earth.

Pamela:                        Hitting Solar Dynamic Orbiter. Well, we also, so this is where Solar Dynamic Orbiter has so far played such an important role. This little spacecraft that can is sitting out balanced between the gravity of the Earth and the Sun, close enough to the Sun that particles hit it. And, thanks to the speed of light being so much faster than the speed of particles, it can go, “Earth, there’s stuff coming.”

Fraser:                         Yeah.

Pamela:                        And, we can safety things. We can send astronauts for cover if we need to.

Fraser:                         Yeah.

Pamela:                        And, that early warning is amazing. Now, what would be even better is – is, predictive models. This is the – the difference between looking at radar right now and seeing a tornado on radar heading towards your house and having satellite images that allow you to predict a potentially dangerous storm is brewing.

Fraser:                         Right, yeah.

Pamela:                        Right now we use spacecraft to predict weather on Earth. Well now, we’re gonna use Earth-based telescopes to predict weather on the Sun more effectively than we can do with spacecraft. And, I love this inner play of how we need all these different kinds of observations to make sense of what we’re learning. 

Fraser:                         And, the hope here is that we’ll get of couple days of notice. That astronomers will see these features on the Sun, see them brewing, see a – a burp forming on the Sun.

Pamela:                        Yes.

Fraser:                         That’s going – and – and understand how all of these – these pieces are connected, right? When you look at that picture of the – of the roiling, bubbling surface of the Sun, how do you know that any, one of those areas is about to cause a – a coronal mass ejection? It’s just, you just don’t. And so, but being able to sort of trackback and use as you say these predictive models of the Sun, we’ll get to this point where suddenly now astronomers can look at all these regions and go, “Okay.”

Pamela:                        Yeah.

Fraser:                         “It – you wouldn’t have known before but now we do know that this region right here that is slowly rotating towards the Earth, like the Death Star, is about to let off a blast that could cause us a problem. And so, unplug the electronics that you care about.”

Pamela:                        And, what’s more, as we’re looking to start putting human beings in space outside of the Earth’s magnetic field, Moon, Mars, wherever. We may only have a small volume of space that is adequately protected from radiation that they can stay healthy if their spacecraft gets hit by a burst of energy from the Sun. Having this kind of predictive model will tell them perhaps ahead of time, “Hey, maybe you wanna come back to the Earth a few days earlier if you’re on the Moon. Hey, get ready to go into hiding as you’re on your way – way to Mars.” We are lucky to have our magnetic fields. And so, we first of all need to be afraid, just like you say of, of another, what we call a Carrington Event, a massive burst of energy from the Sun capable of doing bad things to our power grid, to our satellites, to our astronauts, and lower Earth orbit. We also need to be able to predict what’s gonna happen at the Moon, at Mars. All of these things are necessary to keep the science flowing and the humans alive so.

Fraser:                         Well, and I wanna know when I should go and see auroras.

Pamela:                        Well, yeah. That’s true too.

Fraser:                         But, right now all we get is we get a couple hours of warning that there’s auroral activity. Not even, we get there’s auroral activity right now. Well, it’s too late for me to book my trip to Iceland. But, if I could get two days’ notice that’s there’s gonna a big storm coming, then I can book my trip to Iceland and go and enjoy powerful auroras.

Pamela:                        I was gonna say road trip to Canada, but sure.

Fraser:                         Sure, that place, yeah. It’s a big country. It’s easier to fly to Iceland than to road trip in Canada.

Pamela:                        That’s probably true.

Fraser:                         And, it’s much better equipped than, Northern Canada is a – is a hard place to be. While, I gotta say, being in Iceland is a – is a, quite the luxurious experience. I quite liked it, even in the wintertime, right? Wintertime in Iceland is delightful compared to wintertime in Canada.

Pamela:                        Still on the bucket list.           

Fraser:                         Yeah, yeah. So, I mean this – all we’ve seen right now is the first light images. Chances are you’re gonna bored of because every image is – kinda look like this, just different flavors of variations on roiling plasma on the surface of the Sun. But, we are gonna see Sunspots –

Pamela:                        Yes.

Fraser:                         And other interesting features over time as well. So – so, stay tuned.

Pamela:                        Now, this instrument – this instrument won’t be fully built until this summer. They’re aiming for –

Fraser:                         Yeah.

Pamela:                        Having all the spectrographs, all the polarimeters, all of the devices that will allow us to study even more effectively, the – the outer layers, the temperature, the magnetic fields. This summer, it’s coming. We just have first light.

Fraser:                         Yeah, yeah. So, more instruments coming. So, stay tuned. Right on, I’m – I’m super excited about this and I did a video on my YouTube channel as well. So, if people wanna follow even more information, they can follow that there. Pamela, do you have some names for us this week?

Pamela:                        I – I do. As always, we are brought to you by you. We are so grateful to all of our Patreons.

Fraser:                         That’s very recursive.

Pamela:                        Well, it’s true, it’s true.

Fraser:                         Yep.

Pamela:                        We – we are so grateful to all of our patrons over on patreon.com/astronomycast. If you can support us, please do. If you can’t, we totally get it. Just leave us your review somewhere. Help people find our show, we’re good. So, I really wanna thank this week Jordan Young, Burry Gowen, Frada Tombow, Ramji Enamuthu, Andrew Palestra, David Truog, Brian Cagle, The Giant Nothing, Laura Kettleson, Robert Palsma, Corey Davolli, Paul Garman, Les Howard, Joe Cunningham, Emily Patterson, A Blip in the Universe, Infinitesimal Ripple in Space-Time, and Ed.

Fraser:                         Awesome. Thank you everybody, and – and as always, Pamela thank you for bringing the knowledge. And, we will see everyone next week.

Pamela:                        Sounds great. See you all later.

Fraser:                         Bye-bye.

[No dictation] [00:28:48 – 00:29:18]

Speaker 3:                   Thank you for listening to Astronomy Cast, a nonprofit resource provided by the Planetary Science Institute, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at info@astronomycast.com, tweet us @astronomycast, like us on Facebook, and watch us on YouTube. We record our show live every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 1900 UTC. Our intro music was provided by David Joseph Wesley, the outro music is by Travis Serle, and the show was edited by Susie Murph.

[End of Audio]

Duration: 30 minutes

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