The Moon in Radio Colours - Dr Natasha Hurley Walker’s

[Talks Archive Prerecorded intro]  You're listening to the Western Australian Museum Boola Bardip talks archive. The museum boulevard. It hosts a series of thought-provoking talks and conversations tackling big issues, questions and ideas. The talks archive is recorded on Whadjuk Nyoongar Boodjar. The Western Australian Museum acknowledges and respects the traditional owners of their ancestral lands, waters and skies. 

Boola Bardip Facilitator: Good evening everybody and welcome to the WA Museum Boola Bardip and this To The Moon and Lunar Lounge exhibition. Before we get started with our guest speaker this evening, I'd like to just take a moment to acknowledge, acknowledge the lands on which we are gathered and learning on here tonight. The lands of the Whadjuk people of the Nyoongar nation. 

May we pay respects to Elders, past and present, and extend those respects to any First Nations folks here with us tonight.  

So we have a very fascinating talk tonight. It is Moonlight Radio and our guest speaker, please make them feel welcome, is Associate Professor Natasha Hurley- Walker.  

Associate Professor Natasha Hurley- Walker: Hello, everybody and thanks so much for coming out tonight. It's great to see so many fans of the Moon and we appreciate it.  

So as you can see, I'm dressed on theme tonight. This is Dangerfield. Very beautiful. And, as you can see, this is, this is called, it's a phase, which is, you know, delightful at one point but there is a little quiz at the end. There's something terribly wrong with this jumper.  

So I'm going to hang it here and in case you get completely lost or distracted at any point during my talk, you can just look at my jumper and see if you can work out what's wrong with it. So just.  

Oh, it's gone silent in the meantime. Exciting.  

There we go. the Moon fans already can see what's terribly wrong with this jumper.  

Okay, so thank you all for coming out. I'm a radio astronomer, so this talk tonight is going to focus around the Moon and what, how it interacts with radio astronomy in all sorts of delightful and surprising ways. 

 The Moon is our friend for the most part, in radio astronomy. 

I work at the International Centre for Radio Astronomy Research, which is a large group of radio astronomers. There's actually about 300 of us now here in Perth and, we're a joint venture between Curtin University, where I work, and the University of Western Australia.  

And we're all here because we are building, here in Western Australia, the world's largest radio telescope, the Square Kilometre Array. 

And we have been working toward this for many, many years. It's going to be the biggest, most sensitive instrument. It's going to peer back into the cosmic history. It's going to maybe look for life on distant planets, all sorts of exciting things.  

And, it's being built up in the Murchison Shire, of Western Australia.  

So this is a picture of me [referring to picture in slides]. We did a documentary that showed here last year maybe the year before called Beyond The Milky Way. Maybe some of you saw it, all about this beautiful observatory. So this is Inyarrimanha Ilgari Bundara, the CSIRO Murchison radio astronomy observatory.  

One of the most radio quiet locations on Earth and we have indigenous land use agreement with the wonderful Wajarri Yamaji.  

We have a representative here tonight as well so they have made us feel very welcome and it's a delight to use their beautiful landscape and, and have a telescopes there.  

So the reason that we built it in Western Australia was so far away from, you know, many other population centres is because all of these electronic devices that we're holding now are emitting radio waves and the signals that we want to tune into in the cosmos are some of the faintest in the universe. 

And so, you know, my phone, my computer, all of these things around us would completely, swamp any signal. So we've built our telescopes up there.  

Now, this picture is of the Murchison Widefield Array [Referring to slides]. It's a telescope I've been using for over ten years. I love it. It looks very… not like a telescope, right? It looks like a, series of small spiders sitting on the ground. 

That's okay. Radio telescopes come in lots of shapes and sizes. And this one, turns into some of the lowest frequencies, of light. And I'll show you some pictures that it made a bit later. But first we want to get on to the main event, which is the Moon.  

Now I'm going to start with a wavelength you're probably more familiar with. This is optical [referring to slide]. This is what a radio astronomer would call an optical image. Everyone else would just call it an image and you can see I've picked the prettiest optical image that I can. The Moon commonly is displayed as a sort of black and white image but actually, it is ever so subtly, slightly colourful. 

And if we up the contrast on our colour photographs, we can actually see different mineral composition all over the Moon. That's very cool. Not the subject of my talk, but very pretty.  

Now, light is part of the electromagnetic spectrum, and the wavelengths that we can see with our eyes these optical wavelengths are, is part of that spectrum. 

So when we're doing radio observations we're going down to the longer wavelengths. So we'll take a little journey down through the longer wavelengths. This is an infrared image of the Moon.  

Nowadays you can get these wonderful infrared cameras. I don't know if any of you had a play. They sometimes have them in museums, tell you your body temperature. They look pretty cool. 

If you look at this, the Moon, normally with an infrared camera, if the sun is shining on it, it's unbelievably bright because the sun is heating up to the Moon and making it very hot and that makes it emit a lot of infrared radio, infrared radiation.  

What the photographer has done here, which is quite clever, is they've taken an image of the Moon in infrared during an eclipse. 

So what we're seeing is the subtle, pattern of thermal radiation, so heat coming off the Moon, and you can see that some of the areas that were dark before are now light.  

And a little subtle. Point I just want to point out here. These photos were taken in different locations around the Earth. So we're seeing the moon from ever so slightly different angles but we are still seeing the same face of the Moon. 

 So the moon is locked to the Earth and it always points at us with the same face. If you want to look just behind you, the side with the darker patches, that's the near side of the Moon, and that's the side of the Moon that you'll see, whenever you go out at night and the Moon is up, whereas the other side is very strange. It's actually quite an unfamiliar view. And that's the far side.  

Anyway, let's continue our tour. So this is the infrared view [refers to slides]. Now let's go to a longer wavelength. So let's go to the, the wavelengths that I'm excited about. This is the radio view of the Moon [refers to slides].  

You might think I've just made a mistake and I've just gone back to the optical, but I've got, like, an eclipse or something. No, this is this is what the radio Moon looks like. And I've done something subtle here.  

I'm looking at a particular kind of radio light, and this is called polarized light. I'll explain a little bit more in a middle… a minute, but it is a little bit of an old view. Right. You've got this, this bright light around the Moon and then it's dark in the middle. You can kind of make out some of the craters.  

And this one was made with the Meerkat radio telescope [refers to slides], which, is being built in South Africa, where the other half of the Square Kilometre Array will be located. So we're kind of doing a big square kilometre array intro in this talk. 

All right. So this this image of the Moon is a little bit strange, right? Well, what are we seeing here? With, with infrared, we’re seeing the thermal radiation. With optical , we were seeing the reflected sunlight. So is this maybe one of those things? That's a little unclear.  

Before I tell you the answer, I want to show you an even more beautiful radio image. And this one was made with the Australian SKA Pathfinder, which is another radio telescope near the Murchison Widefield Array. 

It's so colourful [refers to slides]. It's really pretty. Now, in this view, the Moon looks like, a beautiful soap bubble, right? It's, it's a really beautiful colour and if you notice, the colours are really symmetric, right? And this is because what I'm plotting here is the angle of the radio waves.  

So if you look really carefully, you'll see that the colours are all symmetric on either side and that's because they are coming in at a certain angle. So I'm going to put it all together. Now you've, you've actually seen this phenomenon every time you go to the beach you'll have seen polarized light.  

If you go to the beach, if you've got a good pair of sunglasses, I'm, you will look like very professional people. I'm sure you have very nice sunglasses, you get that terrible glare of the ocean right where it's really rippling. It really catches you in the eyes and the sky is almost why it's so bright. 

Put on a polarized pair of sunglasses and it just instantly becomes dark blue. The sky becomes this gorgeous shade. That's because those polarized sunglasses have a little filter that blocks all of the light that is being reflected, that has that particular angle.  

Works wonders if you're driving in wet weather as well, right? Because the light comes in and it gets reflected at certain angles. It has a certain polarization. What we're doing with the telescope is really similar. We can pick out the polarization.  

So this view is actually looking at that. And what we're finding is that the radio waves get reflected off the Moon and they all end up coming in a certain angle. 

The ones that are not at that angle just get absorbed. So you end up with this really, really polarized view of the Moon, which is quite cool.  In the same way that lights are reflecting off waves at the ocean, radio waves reflecting off the Moon and coming to us.  

Well, that sounds very academic, right? It's just a pretty picture. 

It actually is incredibly useful. And this is part one of my toolkit of how the Moon helps radio astronomers. So we have lots of distant things in the universe. This is a galaxy that you can see with your eyes, well, okay, a really good telescope, and it's actually filled with cosmic magnetic fields with electrons whizzing around them and generating radio waves, which is very cool for astronomers like me. 

The problem is that those magnetic fields, we have absolutely no idea what that orientation is. They’re generating polarized radio waves but we can't measure the angle because we don't know what that angle is. Our telescopes can't really tell us without having an idea of what the angle should be. 

The cool thing is we always know where the Moon is, so we always know the angle of these radio waves. So we can use that to work out what the magnetic fields look like in distant galaxies. 

And that is a really cool technique. Like, we would not be able to do this nearly as well without the Moon. So already the Moon is proving extremely helpful to radio astronomers.  

Now, that's probably the most technical thing I'm going to include in this talk, but I hope you all come away with a neat impression of the radio Moon. 

All right, so the next stage of my talk, I want to talk about something that you probably a little bit more familiar with. I want you to cast your mind back to the heady days of April 2023, when here in Western Australia, we got the view of a cosmic spectacle which is a real once in a lifetime opportunity. I am, of course, talking about the total solar eclipse. 

Did anybody go up to Exmouth and see the… oh, I got a few here. Yes. I'm sure you had the best view, like the 20,000 other people here on this crystal clear day of watching the Moon pass in front of the sun. And when it does that, you know, you see all these gorgeous prominences. It's a fabulous view. 

I couldn't make it. I had little kids. They got in the way. But that was fine. we ran a really nice community event down here in Perth, from my local neighbourhood. We did a partial solar eclipse viewing. So the moon is partly blocking the light from the sun.  

If you're ever, lucky enough to know there's a partial solar eclipse going on, and you don't have a pair of eclipse glasses to hand, you can use a colander. You get a really nice view through a colander at the bottom left. It's quite nice.  

And, yeah, we had a solar telescope. We had hundreds of people show up. It was really nice.  And so because we were a little bit lower latitude, the moon didn't perfectly cover the sun for us. But it was it was still very cool. 

Now, where is she going with this? We're talking about the radio Moon. I’m getting back to it. I'm getting back to it.  

Okay, so, radio telescopes lie about halfway between Exmouth and Perth and so they got a good view of the eclipse as well. A little bit of in-between view. Not a total solar eclipse and not the 72% partial that we had, but about an 85% on 90%. 

And so this is a view of the radio sun being eclipsed by the Moon [refers to slides]. Now the sun is staggeringly bright. Right. And the reason that this image is constantly changing is because it's very active. It has these big magnetic fields coming up. Big prominences. They can sometimes shoot, massive, plasma bubbles at us and that's caused some beautiful aurora in the last couple of months. 

And so that radio emission makes it very, very variable.  When the moon passes in front of it, that all gets eclipsed. Well, this is all very cool. Again, looks a little bit academic, right? But once again, I'm going to show you how this can be extremely useful to radio astronomers and therefore to all of us, because that helps us explore the universe. 

We're going to cast our minds back now even further, not just to last year, but to the 1960s. I find it difficult to imagine this because I wasn't there but, maybe some of you might remember this from childhood memories, I don't know.  

So in the 1960s, we still didn't really understand the structure of the universe. We didn't really understand a lot about the cosmos. 

That's because we were mostly just using optical telescopes here on Earth. We hadn't cracked the space race, right? We hadn't launched people up there. We hadn't put powerful satellites in orbit and we were still using just this tiny part of the electromagnetic spectrum.  

And what we were seeing was some weird things that we didn't really understand. We could see stars, we'd see what were called nebulae at the time, we didn't really understand galaxies very well at that point.  

But there were these very, very weird stars that were very, very, very bright and they had very, very strange spectra. Their colours were also sort of strange colours. It didn't really make sense. And some of them had these strange little fuzzy jets coming out of them, which again, didn't really make sense. You know, people couldn't work out what these things were.  

At the same time, we were inventing radio astronomy. And, Australia was one of the pioneering countries that did really incredible work. in, in radio astronomy. So this is our first big national facility, the Parkes radio telescope. We needed to make a quick movie to make some money.  

Anyway, So the dish is incredible. It's built in a sheep paddock, in New South Wales, and it's been working hard for us for over 50 years, giving us a beautiful view of the cosmos.  

So, all right, we've got this weird puzzle. Let's point the foremost Australian national facility at the puzzle, Okay. Not great. Right?  

The problem with radio telescopes is unless you join a lot of them together, if you just have one big dish, very poor resolution. This is about what Parkes would see when looking at that system [refers to slides]. It doesn't really tell you anything. There's a blob there. Thanks, Parkes. 

So here is where the Moon comes in. I know you're thinking, where is she going with this? All right. Just yesterday, there was a fabulous photo, on astrophotography interwebs about an occultation which is where two objects in the solar system line up. This is Saturn and the Moon. 

I couldn't get an image that would really look great here. So I have made my own, time lapse using the technology to which I have access, which is called PowerPoint and we're going to watch, this very not to scale Saturn go through an occultation with the Moon.  

[watches PowerPoint with audience] All right. There we go. 

That was a beautiful occultation. I'm sure you'll agree.  

So it's it's all seriousness though this is very useful for astronomers because if you imagine what's happening when Saturn goes behind the Moon, if you're just looking at Saturn, it appears to be bright and then it appears to be dim, and then it comes out the other side and it's bright again. 

Cool. If you didn't have the beautiful resolution, this is a Hubble Space Telescope image of Saturn, then you could actually use that change in brightness to measure its shape. So in 1963, using the Parkes radio telescope, that is exactly what some of Australia's really thoughtful, clever radio astronomers figured they could do. They took the fuzzy blob that would have been the Parkes image, and they waited with the telescope poised at the limb of the Moon at exactly the right moment, and watched it get occulted by the Moon. There we go. That's my, it's my diagram, it's great, right. So this is a kind of, zoomed in view of what they saw. So as the source comes out from the side of the Moon, you see a little lift in brightness, and then a minute later you see another lift. 

So it's actually made of two components. Don't worry, I'm not going to make you do all of the math in your head. They've done it for us. So this is an image from the 1963 paper in Nature that showed, for the very first time that, these objects are very, very tiny, but very, very, very bright in radio and they consist of a core that is exactly over the top of that bright spot, and then a big, long trail that comes outward.  

That was 50 years ago,  60 years ago now, and ten years ago this is a modern radio telescope image of the same system. And you can see it is spot on. Using a telescope that had no more resolution than your thumb held out at arm's length they were able to probe the tiniest details on the sky, again using the Moon. Very cool.  

Okay, again, why is she telling us these academic things? Well, it is actually one of the most fundamental discoveries that, humankind has ever made. That picture, that's not a star. With the radio, you can work out, that is actually a black hole. That was the first detection of a black hole in our universe. And not only was it a black hole in a distant galaxy, you know, a billion solar masses, it's spitting out a jet that moves at nearly the speed of light. It challenged and changed our understanding of astrophysics forever.  

And nowadays there are thousands of us astronomers all working on these kinds of galaxies. It's a really exciting field of research and we would never have been able to do it without the Moon.  

So that's my second toolkit, item in my toolkit, of how the Moon is useful.  

All right. I'm gonna get on to the third stage of the talk. Has anyone worked out what's wrong with this jumper yet? Yeah, a few people are nodding, right. What? When you look at, when you realize you're like, oh my God, what were they thinking? What's that? What's, what's happened? Okay, tell me at the end.  

All right. So the, the third stage of my talk, brings me back to my favourite telescope, the Murchison Widefield Array. I'm going to show you beautiful vision of galaxies billions of light years away to the MWA. They look like blobs [Laughing]. So those, every single one of those little dots there, is one of those amazing supermassive black holes, right. Okay. Our telescope doesn't have that much resolution. It, they look like little dots, better than Parkes, better than Parkes, but they’re still like little dots. And what I'm showing here is the Moon zooming through the image, this is slightly sped up, and you can actually see the dots winking out as the Moon passes them. So this is another kind of eclipse. We're actually eclipsing distant radio sources. But there's also this blob in the middle, right. And that wasn't in the first image I showed you. What's happening? Has the Moon suddenly become a transmitter, so suddenly sending radio signals directly at Earth, we're all going to be annihilated? 

No. That frequency down there is the frequency at which we're observing 98 megahertz. Does that ring any bells to anybody in the audience? In sort of frequencies. How about 99.3? Yeah, that's Triple J. Oh, dear. So what's happening there is the radio equivalent of Earthshine. That Earthshine’s fabulous, all right. Astrophotographers love it. This is when the reflected sunlight from the Earth illuminates the Moon and so you can see this sort of pale shadow of the Moon. It's really, really gorgeous. If you look at, look on a dark night, the crescent Moon, and you can just about make out the Earthshine. That's fabulous. Radio Earthshine, not so fabulous. So we have all of the human race on their cell phones and listening to the radio, sending out radio waves in all directions. 

Some of those radio waves hit the Moon, and then they're reflected back to us. A little bit dimmer obviously, they've had to travel through space and come back to us, but that's why we're seeing the radio brightness on the Moon like that. And so what we're seeing here is a bit like a convex mirror. If you imagine a, no if you took like, mixing bowl, a metal mixing bowl, and you looked at your face in it, you would, you'd see a very strange reflection of your room, right? 

And that's because all the radio waves that are coming from other angles get bounced off in the other direction. But looking straight at the Moon, those ones come straight back. So that's the explanation for what we're seeing. And again, thinking, how could that possibly be useful? It's just a really, really big cosmic selfie. And I've dubbed all of our radio stations mixed together. 

Well, it is useful. Has anybody seen this show? Yeah, a few people. Cool. All right. I just watched it. I thought it was great. I, Oxford does not have a particle accelerator. Also, particle accelerators are different from neutrino detectors, but, right. And they need better physicists on this show. But the show is really cool, right. And mild spoilers, part of the premise of the show is that a radio astronomer a little bit pissed off, a bit more pissed off with the world than I am. Luckily, you're all very lucky, uses this radio telescope to send a message to an alien civilization and says, you know, we're not doing a great job here on Earth. Can you come and run this show for us because I think it would do a better job.  

So she sends that message just using this telescope. Okay. And some really fuzzy solar physics. Well, it's kind of worrying, right? I mean, if you've seen the show, it's not going well. We are constantly currently broadcasting everything. We're broadcasting this show. Right? What if aliens see this? What if they see War of the Worlds, which was broadcast 100 years ago? 

It would be really, really nice if we could know how bright our radio signals are, that are going, when they're going to other planets. Could those aliens be tuning in to all our problems and thinking, yeah, we could do a better job of running this than you guys?  

Well, no surprise, right? The Moon. The answer is always the Moon. The Moon can help us solve this problem. So here we have our distant alien species. The Earth is emitting in all directions. And so those radio waves are going to get there eventually. Well, we can calculate how bright those radio waves would be by looking at the brightness of the Moon’s, of the, of the radio waves reflected off the Moon. 

We can just do some maths because we know the distance between the Earth and the Moon, so we can work out how, how bright they would be to the alien civilization, which is pretty cool. I'm sure you're all wondering [Laughs], do I need to pack my bags and get into my bunker? When do I, when do I panic? When do I start worrying about this? 

Well, luckily, ten years ago, a colleague of mine, Ben McKinley, wrote a lovely paper, we actually did this calculation. We measured the Moon using the Murchison Widefield Array. We worked out that, our civilization, our whole civilization, is 50 times dimmer than the Sun. So if you were looking at our solar system, you'd have to subtract the Sun to find us, which is kind of disappointing. 

But I have to say, do you think that's pretty good? Right? Like, the Sun is a mass of incandescent gas, a gigantic nuclear furnace with hydrogen and helium being fused at temperatures of billions of degrees. No, they might be giant Suns, okay, and we're just like monkeys with cell phones, and we're, we're still, like, 1 or 2% of the Sun,so I think that's pretty cool, if a little bit disappointing.  

All right. So it's disappointing in the sense that I think we could do better, but it's also great because I'm not going to start seeing numbers in front of my eyes anytime soon. So that's my third way in which the, the Moon is helpful.  

I wanted to conclude this talk, with a little bit of a forward outlook, and also, I can finally, you know, get off the stage and stop telling you about all my regolith, all my lunar material.  

All right, to conclude the talk. So where are we going? How can the Moon be helpful to radio astronomy in the future? Well, all of that radio waves that I just showed you, all of them reflecting off the Moon and coming back to us, all the satellites we're putting in orbit could be a bit of a problem. All right, that's making it a little bit harder to tune in to those cosmic signals that we're so interested in.  

So why not build an observatory that's shielded from the radio waves that we're emitting? And early on, I told you, same face of the Moon is always pointing towards us. So I'm sure you're thinking what I'm thinking. Why don't we build an observatory on the other side of the Moon? That would be great, right? People are genuinely thinking about this. Craters are a very convenient shape for a radio telescope, and this side of the Moon would be permanently facing away from the Earth, so no cell phones, no Wi-Fi, clear, unobstructed view of the cosmos. 

All we need to do is figure out how to get several tons of metal to the other side of the Moon, and then when we collect the data, we need to somehow get it back, despite the fact that we're now on the wrong side of the Moon. But I think it would be very cool. I'm not volunteering to go work at this observatory, but I do think it would be really neat if we could build something like this in the future. 

So, with that, that is almost to the end of my talk. I really hope that you enjoyed it very much. If you would like to see any other talks by me, this is the very first time I've given one about the Moon. I didn't know how it, how many things I would have to cover, and I still left things out, but I give a fair few number of talks around Perth. There's more stuff on my website, so if you're interested in hearing more from me, you can check it out there. Or I'll be around, circulating, so feel free to chat to me. And I think I'm going to take some questions as well. So thank you very much and thanks for your attention. 

Cheers. 

[Audience applause] 

Facilitator:  Wonderful. We've got time for probably about three questions if anyone wants to ask anything. Yeah, perfect. I'll bring the microphone over.  

Audience Question 1: You know how you said there's that mobile, all the, right, you know, stuff going out there? Does it ever end? Like, does it, does it die? Or does it just keep going through the Universe? 

NH-W: So it keeps going through the Universe, but it gets fainter and fainter with the square of the distance away from us. So that becomes very faint, very quickly, which is why our civilization is so dim compared to the Sun. That, well, you know, they're both dim, at a distance. So, you know, in a sense, those signals will always be there in the Universe. You can never take away the history that we have broadcast into space, but it would become decreasingly detectable, and you would struggle, really, to tune in.  

The nearest star system, Proxima Centauri, if you built this ten, something ten times bigger than the Square Kilometre Array, you would just about be able to tell that we were here. But, you know, we'll see what we build in the future. Or maybe they'll be a really pissed off radio astronomer who deliberately sends a message (laughs) 

Audience Question 2: How much difficulty is Elon Musk satellites causing? Basically, he put in, like, hundreds of them. Is this causing a lot of problems? Can you subtract that exact radiowave or sort of work around it?  

NH-W: Yeah, a little bit of both. So, what they're working on at the moment is a few different things. 

So we're working with the satellite operators for starters, it's not an antagonistic relationship. They don't want to ruin the night sky either. So that the, you know, for the optical astronomers, they're painting them black and making sure they're not too reflective for us. They're making sure that when they're over the radio observatories, they're not transmitting directly on top of us,  and also there are different frequencies that we use, and there are frequencies if they just stick to those frequencies, we can't see them. Essentially, what's a little bit more uncontrollable is the reflections off the satellites. So we've got that reflection of the moon, you could also get reflections off the satellites. That's a little bit more difficult, it is a really hard problem. 

So, there's a lot of people working on clever software to try and remove those signals. but yeah, it's not a solved problem,  Thanks, it's a great question.  

Facilitator: Any last questions? We’ve got time for one more. Yes, one more at the back. 

Audience Question 3: As a general question, is it possible that, let's say we try to get to further planets and use the moon as a Wi-Fi router for further travel rather than extend our signal for that? Would that be possible. 

NH-W: Interesting point! I guess so, but I also think that if you have the technology to build, a radio relay station on the moon, you would probably just build them in space , free floating, and kind of boost your signal that way. 

Because the problem with, you know, the moon is that you can only get to, like, the surface of it, and then that surface can only point in a certain direction and can't go through the moon. Whereas if you pointed at a free floating transmitter, it could rebroadcast your signal in any direction. 

Off the top of my head, I think of free floating, you know, just freely in orbit, slightly outside the Earth's orbit. I think that would be more useful to people, but maybe I'm just trying to preserve my lunar observatory on the far side of the moon (laughs) and make sure there's no Wi-Fi signals contaminating it. So yeah. 

Thanks. Cool question. 

Facilitator: Fantastic, that concludes our talk for this evening. Please give Professor Natasha Hurley Walker another round of applause.  

N H-W: Thanks all.