University Place  Eric Hooper Badger Astronomers Spanning the Globe  UP838 February 12, 2013    cc >> Welcome to UW Space Place. I'm Jim Lattis, and tonight we have our guest speaker, will be astronomer Dr. Eric Hooper from the UW-Madison Astronomy Department. Eric does a lot of observational astronomy, has worked on some of the biggest telescopes in the world. But Wisconsin astronomers spread out all around the globe, so Eric is going to tell us tonight about Badger Astronomers Spanning the Globe. Eric. >> Thank you, Jim. Thank you, everybody, for coming out and joining us tonight. I appreciate you being here. As Jim mentioned, we're going to talk about several different observatories that UW Madison astronomers are involved in. We're going to mostly just focus on the ones that utilize visible and infrared light and are located on the ground, on the Earth. 

We also use quite frequently telescopes that involve other types of light, other wavelengths of light. That's a whole other discussion. We can have that another time. And we also utilize telescopes that are in space. So the cornucopia of instruments that are available for doing our research is even more than we're going to talk about tonight, and yet we have plenty to go through just sticking with the ones on the ground. Now, you may wonder why in the world have telescopes that are in Arizona, are in Chile, and are in South Africa, why not right here in Wisconsin? And the truth is we do have some observatories and some instruments that are here in Wisconsin. There's the venerable Washburn Observatory on UW-Madison campus. There's also Pine Bluff Observatory outside of town. Why aren't those enough? In fact, you could go back even farther in history. What I have here is a replica, a modern replica of Galileo's telescope. 

So this is how big it was. This is what he used for all the revolutionary discoveries when he just took this simple device and looked up into the sky. So what was good enough for him is not good enough for us. Why not? This is easy to use. It's portable. You can take it anywhere in the world. What's wrong with this? So we're going to go through and discuss some of the desiderata, some of the aspects of telescopes and their instruments that are particularly important for modern astronomy. And we can ask, why isn't Galileo's telescope enough for all of us today? Why isn't any one of our telescopes, either in Arizona or Chile or South Africa, good enough for everything we want to do? So, to begin this discussion, let's talk about the perfect telescope. If we had the perfect telescope, we would only need one. And here are some of the features of that perfect telescope. 

Starting from the top there. Large size aperture, I'll talk about that a little bit more in a second, but the bigger the aperture, the bigger the opening that lets light through, the better the telescope is in the sense that it can collect more light. You can see fainter objects. You can see objects of the same intrinsic brightness that are farther away. It's very important. And already poor Galileo's telescope is falling down here. As you'll see as we go through this discussion, modern research telescopes are much, much bigger than this. The apertures are much larger. So it would serve Galileo very well for revolutionary discoveries. It's just too small for us today. 

As we go on down the list here, the next one, clear skies all of the time. Well, this would be handy for it because if the skies aren't clear where you are, you just put it under your arm, walk to where the skies are clear or ride a horse or take a car now. So that's one advantage this has. Third, excellent image quality. With all due respect to the lens makers in Galileo's time, and even the modern ones who produced this, the image quality through here isn't quite up to snuff. Want to be able to see all wavelengths of light or all different colors of light, and that's true. With this, we can see all of the visible light colors, the ones we're used to seeing with our eyes, because the instrument on the back end of this telescope is our eyes. Any color we can see with our eyes, we can see with this telescope. But there's a lot more than visible light out there. There's infrared light. 

There's radio light. There's ultraviolet light. X-rays. All these different types of wavelengths of light that are not accessible to this because we're using our eye for our instrument. See the entire sky. Well, we can see the northern sky just fine with this from here right outside the parking lot, but we can't see the far southern sky. For that we'd have to go to the southern hemisphere. So that's another reason why you want more than one telescope. One in the north, one in the south, at the very least. And yes, you could do that with this. 

You could carry this to the southern hemisphere, but again, we're seeing it has some of these other limitations. You'd like to be able to put all different types of instruments on here. Instruments are devices that allow you to analyze, record, and study in great detail the light that's coming through the telescope from a source up in the sky. The simplest instrument is just a camera. Actually, even simpler than that, the simplest instrument is our eye, and that's what Galileo was using. He was able to just look through here, but beyond that, he couldn't change out his instruments. He didn't have spare eyes that could see an infrared light, for example. He didn't have an extra set of eyes that could see in radio waves. So he was stuck with just what he could see through his own eyes there. Modern telescopes, as you'll see, have a cornucopia of different instruments on them that allow us to analyze the light that's coming through in a variety of ways, kind of amazing ways. 

I wish I'd thought of a lot of these things, but I didn't. People were more clever than I to figure that out. You want to have a telescope ideally that's easy to access and easy to work on. Well, this one certainly wins there. What kind of telescope would not win there? Let's think about it. Easy to access and easy to work on. If it's on Earth and it's not too far away, you could do that. If it's very far away, say in South Africa, that's a little harder. It takes a day to get there with all the airline connections along the flight. If it's in space, it gets harder still. 

Very expensive, takes a long time and a big effort to get up there, and that's only if it's in the Earth orbit. A lot of modern space telescopes are away from the Earth orbit and are not accessible. We can't get to them. So, as to this point, the easy access and the ability to work on it, space telescopes pretty much you cannot do that at all. Then you want vast amounts of observing time for everyone. That's a little hard. Astronomers tend to be a bit greedy. If there's only one of these, that's a problem. So you want to have access to more than one kind of telescope that has different kinds of instruments on it so people who are interested in some things can use one telescope, others who are interested in other things can use a different telescope. And finally, ideally, you want it cheap. 

You don't want to pay a lot for this. This one certainly wins in that, but again, because of the other limitations, we've gone on to bigger telescopes with more modern instruments on them, and those aren't so cheap. So it's this combination of all of these characteristics here that we're trying to do to get a perfect telescope. And as we've talked about, and you can imagine a lot of other different scenarios, you just can't get all of these completely optimized. And that's the fundamental reason for having more than one telescope.  Let's start on a little tour of various telescopes that UW-Madison astronomers have direct access to. Again, we're going to confine ourselves to the Earth. And as we start heading there, I actually am going to talk about a space telescope here just as an example on the way to our tour, and that's one of the criteria that we discussed was the size of the aperture. How big is it. Here's a person for scale. 

This is the Hubble Space Telescope. I put these up there because these are well known. A lot of people have heard of these. This is the size of the primary mirror on the Hubble Space Telescope right here standing next to this person. You can see in comparison, this is the next generation space telescope known as the James Webb Space Telescope. This is a schematic of the mirror over here. One of the things I want to point out is that you actually have an advantage that might be more than you would expect. The new generation mirror is a little bit more than twice as big across, twice the diameter, as this one. You can imagine you could plop that over there. You would see one of them here, another one there, maybe 2.5 times larger. 

But you get a lot more than that in total collecting area. In fact, the collecting area goes up as the square of the diameter of the mirror. And by square I just mean if you have a mirror that's twice as big as another one, the amount of collecting area you have is two times two, or four times larger. If the mirror is three times as big, then it's three times three, or three squared, and nine times larger. So you very quickly build up a lot more collecting area the bigger the mirror you have. And that was one of our big criteria, if you remember, is we want a large collecting area to gather a lot of light to be able to see faint things or to see bright things in finer detail. Another one is the quality of the images. You would like to have sharp images, all else being equal. And here's a comparison to give you a sense of a difference in image quality. On the left is one of the great de facto standards of modern astronomy. 

It's the Hubble Space Telescope. It takes incredibly sharp images. It's because it's above the atmosphere. The atmosphere is turbulent. It jumbles up the light that is coming down to the mirror and jumbles the images. If you've ever looked out across a hot car hood or a parking lot on a hot day, you can see wiggles in the air. There's turbulence in the air. That's happening all the time. Even above us. Even on a cold night. 

It's hardly perceptible except for the twinkling of the stars, but it's there. That messes up the images from the ground. So this is an image taken from the ground of the same pair of galaxies that are interacting. It's about the same size telescope mirror. This mirror from the Sloan Digital Sky Survey, which uses a telescope in New Mexico, it's about the same size as the Hubble Space Telescope, and look at the difference in the clarity. That's due to the lack of atmosphere in space. The Hubble Space Telescope does not have to look through the atmosphere, and the one from the ground does. And different sites on the ground have different levels of image quality, and that will be part of our story. Some of our observatory sites have excellent image quality, even from the ground. Others have more modest, more standard image quality. 

So we have to utilize other strengths of those telescopes. And before we get too far into this, I just want to remind people a little bit at a fundamental level how images are made. When we talk about images, when we talk about pictures, in the modern sense with a digital camera, and basically the telescope cameras, the detectors on telescopes, are just really fancy versions of everyday digital cameras. There's just a lot more expensive and have a little more capabilities, but it's fundamentally the same idea. And to build up an image, like this, this is the same galaxy. We had the pair there. I just isolated one of them. Here's an image, this is the Hubble Space Telescope image, and I'm zooming in here in the center. Zoom in there, go to here. So you can see some of the same features. 

Again, it's just zoomed in. Zoom in a little bit farther. Even with HST things are starting to look a little bit fuzzy. Zoom in even more and you get down to the level of what are called pixels or picture elements. Each of these little squares is a pixel. And it's a digital, a numeric representation of the amount of brightness at that particular position. So what's underneath that square, what's inside the computer, is a number. It's a position on the image and a number. The number tells you the brightness. That's it. 

That's fundamentally all there is to digital imaging in the modern age, whether it's your digital camera or whether it's the detectors on the Hubble Space Telescope. So, bare this in mind, as we're going through and talking about all these different cameras, all these different instruments, I'll be showing you data, some of it raw, some of it processed, it all boils down to a detector like this. So we begin our tour now out in Arizona. This is Kitt Peak. It's a famous observatory site. It's not just our telescopes there. There's a lot of them there. Here are just a few of them. Look, it's a city of telescopes there. Look at all these domes. 

One there, one there, one there, one there, one there. This is taken from the side of the mountain that's near out telescope looking over to the other side. If you went to that far side and looked back, you'd see even more telescopes. So it's just a thicket of telescopes up in Kitt Peak in Arizona. We get back to one of the criteria I mentioned. You want clear skies. Kitt Peak often has clear skies. But you also want dark skies. And there's a growing issue with Kitt Peak. It recently had its 50th anniversary. 

When it was first put up there, Tucson, Phoenix, the nearby cities, Casa Grande, were all much smaller than they are now. They have grown. There's been urban sprawl, and even though the population centers, the counties, the towns around there have been very proactive and very aggressive about containing the light pollution, there are lighting ordinances in these areas to try to keep the light down to preserve the observatories, not only at Kitt Peak but all around Tucson, despite that fact, there's a lot of light. You just can't avoid it. You have millions of people living near an observatory, and you have some bright skies. So this picture down here in the lower left is a perfectly clear sky. There's a little bit of haze on the horizon. This is a nighttime shot. There's stars in here. There's a few of them right there. 

There's one. And the haze is lit up. We're looking to the north. Those are the lights of Casa Grande and Phoenix. And here is a situation that's a little bit worse. There's a little bit of cloud. There's thin cirrus there. Still stars up here, but there's thin cirrus. You can see how bright it is. Granted, this is a time exposure, but it's still quite a bit of light pollution there. 

So that's one of the drawbacks of that site. It's a trade-off. Yes, it's clear most of the time. It's in the desert. Nice skies. But you do have a fair amount of light pollution. Getting on to our telescope. It's called WIYN. It's an acronym. Astronomers use acronyms all the time. 

We have acronyms made up of acronyms. In fact, here's one of them. WIYN stands for Wisconsin, Indiana IU, Yale University, and the National Observatory. So here's the acronym within an acronym. The National Observatory is actually called NOAO for the National Optical Astronomy Observatory. You can see why I didn't write all that out. And these are just a few pictures of the telescope. In the front here is a smaller one. This is also part of the same consortium so UW astronomers have access to that. It's less than a meter, its mirror is less than a meter in diameter. 

Now, that's big compared to Galileo's telescope, but it's pretty small compared to the one behind it. So I'm going to spend most of my time talking about the one behind it, which is this one right here. When we typically refer to the WIYN telescope, this is mostly what we're talking about. This is it here. It's the outside of the dome. These garage door-like structures open up to let air flow through. These big barn doors open to let light come in, and the telescope is inside there. And this is a little bit difficult to see. Probably only some of the people near the front will be able to see that, but this is a nighttime shot showing the same thing. And if you squint hard, you can see here's the zodiacal light. 

This is looking west. Here's the Milky Way going up like that in a V shape.  Some shots from the inside. To give you a sense of scale here, this is one of our undergrad students who was up there with us. This is the back end of the telescope. Look at all this. There's a mess back there of mechanical actuators, hydraulics, electronics. This is a very actively controlled mirror. Most telescopes' mirrors, you just put them there and let them sit. They warm up, they cool down with the changing from day to night. 

And as they do that, their shapes change. If the shape of the mirror changes, it can mess up the quality of your image. Go back to our criteria for the perfect telescope. One of them was image quality, image sharpness. And if your mirror is bending around with temperature changes, that's not very good for your image sharpness. And this site is one of those that I referred to earlier that happens to have excellent natural image quality. So the turbulence in the atmosphere above this site is really good. There's not much turbulence. So you can get very, very good images here. Not as good as in space, but really good. 

But that doesn't do you any good if your mirror is warping and bending and twisting as the temperature changes throughout the night or it's sagging under its own weight. So all of this in here is an active support for it. It actively pushes and pulls all the little actuators to try to keep the mirror surface lined up. There's the primary mirror, the main mirror that collects the light. This is 3.5 meters in diameter. It's pretty big. Again, bigger, collecting more light. And this is an image of the mirror itself. So we got right up where Ryan is here. I got up there and took a picture down in there. 

You can see the mirror reflecting some of the struts here, and these are holes for the light to go through because the light hits the primary mirror, goes up to a second one up here, goes back down through a hole here, and then the instruments are mounted off to the side. The instrument is what actually collect and process the light. Let's talk a little bit about one of those instruments. It's called SparsePak. The name won't mean too much. I just want give it a label, give it a name. It's a really interesting device. It addresses partially a problem that astronomers have. On the one hand, you want to take a picture of the sky and see all the full detail. But on the other hand, you also want to be able to break up the light into its constituent colors because they tell you many different things. 

Separate out the colors very, very finely. Well, that's hard to do because our eyes and our computer screens are used to seeing three colors and the combinations of those. If you want to get finer detail than that, it gets really hard. And astronomers are always trying to find tricks around that. How do you get both the information that's in a picture of the sky and the information that's in the distribution of the colors of the light that's coming from the object? That's a hard thing to do. Well, this is one way to go about doing it. Each of these little circles here is a representation of an optical fiber. Optical fibers are often used throughout the world for transmitting data. It's part of the Internet. They're very good at transmitting data. 

They do it with light. Well, if they're good at transmitting light that contains digital information, they should also be good for capturing light that's coming from the sky, and indeed they are. So the idea here is that there are a bunch of these fibers. Again, these are just representations of them on a picture of the sky. I'll show you what the data actually look like in the next slide. They're representations here. The idea is that each of these fibers gather up all of the light that hits it and sends it down to the instrument, and we can analyze that light separately and individually. And then we can do an independent analysis of the next fiber over. And so we can build up information about these different parts of, in this case a galaxy. We're looking at a distant galaxy that's way outside of our Milky Way galaxy, and we're trying to understand what's going on with the stars there. 

We're trying to understand the history of the stars, how they have formed, how they died throughout the lifetime of the entire galaxy. And the other pictures here, this one right here, is, again I mentioned briefly that we look at other types of light. This is a radio map. So I'm not going to talk about radio telescopes much. I'm just going to say this is from a radio telescope. It's from the Very Large Array in New Mexico, and it's to the same scale. It's showing there's big bubble of radio emission coming out of the center here, the visible image would be out there. So something is going on. What we think is happening is there's a super massive black hole that has been active in the past and blown this big radio bubble out there. So this is part of modern astronomy, trying to understand different components of these objects using different types of light with different telescopes. 

Again, the different types of light tell you different things. You need different telescopes to do them. We get back to why we need more than one telescope. This next one is the same thing again, well actually it's a different galaxy. It's the same instrument but a different galaxy trying to do the same thing. Oops, no it isn't. Let me go... This is in here just to show you an example of natural spectroscopy. Spectroscopy is breaking up the light into its constituent colors. There's a natural one. 

It's a rainbow. This is at Yellowstone Park. That's a geyser, and the water droplets in the air are acting as a natural instrument to break the light up into its constituent colors. And now we go onto the astronomical instrument. And here is a good representation of what I was alluding to initially. We want, ideally, more information than just a few colors, like red, green, and blue. We want more and more and more. Break up the light very, very finely. And what's being shown here on all of these plots, each arrow goes down to one fiber. So remember, these are the different optical fibers looking at different parts of this galaxy, and they go out to a graph. 

The graph shows how bright it is. That's the vertical here, up and down. Higher up, brighter. Lower down, less bright. That's all it is. And along the horizontal axis is the wavelength. I know that the scale is not readable for most people in the room except maybe those up in the very front, but it goes from blue to red. So this is blue light out here, this is red light out there, but the difference is it's very finely chopped up. And you can see discrete features in here. These lines, the trough here. 

Some of these lines right here. This line right there. Those are real features that are coming out of the object and allow us to tell what's going on there. For example, the one in the upper left here is nitrogen. So that tells us nitrogen is there. This is oxygen. We can tell what kind of elements are out there, what kind of molecules are out there, how hot they are, what their pressures are, what their densities are, how fast they're moving, all of this comes from taking the light and breaking it up into this fine distribution of colors. Not just coarse colors, red, green, and blue for example, but this fine distribution of colors. And to do that, you need a specialized instrument called a spectrograph that does effectively what the rainbow did in the previous picture but in much finer detail. Again, if you want to understand the detailed structure of the spectrum of the distribution of light but you also want a picture. 

What I showed you before was one way of doing it. We took an image of the sky and put fibers on there, optical fibers. So we chopped it up into pieces and then spread the spectrum out completely, all the visible light. This next telescope, and this one is in Chile, started out in Kitt Peak in Arizona, went to Chile, this takes the opposite approach. This says I only want to look at one particular spectral feature, one narrow little color from one particular element, doing one particular transition. It's called hydrogen alpha. So we get the Wisconsin Hydrogen Alpha Mapper, or WHAM. And this poster that WHAM produced lives up to its namesake. It's quite a shocking thing when you see it first coming up here, all this stuff going on. Well, what have we got here? I won't take time to go into full detail on all this, but this is a projection of the sky. 

It's a funny way of projecting the sky. It's a map of the sky. It's a map of the sky such that the center of our galaxy in which we live is along here. So it's like a globe of the Earth in a little bit of sense except instead of looking down on the glove we're looking out into space. And instead of the equator of the Earth, this is the equator of the galaxy. This is up, or north, in the galaxy. This is down, or south, in the galaxy. This is along the equator. The brighter it is here, it's been both color coded and brightness coded, the brighter it is, the more of this hydrogen alpha emission line is coming there. It takes a lot of energy to get this line. 

So we are tracking here the energetic processes in our galaxy. And this is a survey of the entire sky. So this is a different operational mode than telescopes typically work in. Most telescopes, the one I showed you before, is primarily used in this mode. An individual astronomer will come and say I want to look at this object or I want to look at that object, and then he or she can command the telescope through a computer, there's an operator to help, and point there and point there, picking out particular objects to study. The galaxies that I showed you in the previous slides with those optical fibers overlaid was an example of that. This one says, all right, instead of doing that, we're just going to look at the entire sky. So why doesn't everybody do that? It takes a lot of time. This is a dedicated telescope. Again, why do you need more than one? This one only does this. 

It's spent its entire lifetime, 15 years roughly now, only doing this. Nothing else. And even after all that time, look what happened. This is the same type of map that we had before but there's a hole in it. I cheated on the last one. We were looking away from the center of the galaxy. This one we're looking toward the center of the galaxy. We're living in a disk. So you can look out along the disk away from the center and then turn around and look toward the center, and I saved us from the dirty little secret is that when we turn and look toward the center there's this big hole here. Why a big hole? It gets back to one of those criteria for the perfect telescope. 

You can observe anywhere in the sky. You can't do that here because the Earth is in the way. This was taken in the northern hemisphere from Kitt Peak. You can't see the entire sky from a place in Arizona. The far southern sky is inaccessible. The Earth is in the way. If you were to see it, you would have to look through the Earth. Now, some type of astronomical detectors can actually see through the Earth in neutrinos, but that's another story. So, since we're not looking at neutrinos, we can't see through the Earth in visible light just like we can't see through the ground here. You have two options. 

You can either build a second one of these in the southern hemisphere or just pick the thing up and move it, and that's what they did. Exactly, yeah, imagine that. You pick up a telescope. Cart it down to Chile. They moved this from Arizona to Chile. Well, that big one that I showed you, that would be really hard to do. This one, however, is kind of small. And you can see here, if you look over on the right side of the image here, these are some fellows down here in Chile, and, there we go, right there, it gives you some scale. This is the telescope right here. This thing is just a trailer with the detectors in here and a whole bunch of computers. 

A lot of stuff. Everything you need to run the telescope is in here. But the telescope itself is pretty small. So, again, you don't necessarily have to have a huge telescope unless there's a reason. This one is able to get away with what it does is it doesn't have very good image quality, deliberately. It has much, much worse image quality than any of the others by design because they wanted to survey the sky relatively quickly. Fifteen years is a long time but still, for the entire sky, it's not bad. And they wanted to be able to collect a lot of light because they didn't have a really big telescope. So there are all of these tradeoffs. So we're starting to see that the perfect telescope doesn't exist. 

You have to trade-off depending on what you want to do. Some work really well for some things but are not going to work very well for others. So you have to have that trait. It's why we have more than one. We've gone from Arizona to Chile, from the northern hemisphere to the southern hemisphere, now let's just stay in the south, go around the world from Chile, to South Africa. And this is another site for one of UW's telescopes. As with all of these, it's not just ours. Remember the one on, well, the WHAM one is, but the one on Kitt Peak, WIYN, Wisconsin, Indiana, Yale, National Observatory, it's not just us. We're in a partnership with many others. This one in South Africa is an even bigger partnership. 

It's called SALT for Southern African Large Telescope. Very imaginative name. And, again, the acronym. We come up with names that are not very imaginative and that are this long so we have to have an acronym to shorten them down because we would drive ourselves crazy saying Southern African Large Telescope all the time. So we just shorten it down to SALT. And yes people have made all sorts of jokes about SALT and pepper. In fact, there's somebody in the room here who I would like to name and who works on instruments for this telescope and would really like to name the next instrument pepper just for that. You get a sense of how international a collaboration this is. I've got the flags of the various partnered countries, and many times within each of these countries there are many institutions. For example, the US is not just Wisconsin, there are other universities. 

Rutgers, for example; Dartmouth, for example; University of North Carolina, for example; Museum of Natural History in New York City. And then there are groups in the UK, Germany, of course South Africa, there's the South African flag down there, Poland, New Zealand, and India. Makes for really interesting meetings and it's a lot of fun. You can travel to these different countries, meet people, it's a cultural mix as well as a scientific mix. So you may be wondering, why South Africa? Well, the reason is because the South Africans were building a telescope there, and it was a good deal. They were building it relatively cheaply. We'll talk a little bit about why they were able to do that. So, again, that criterion, cheap, you want the lowest cost as possible, but they weren't able to do it all themselves and they didn't want to do it all themselves. They wanted some other partners. So, okay, whoever wants to come on in, you can join us, help contribute to the operation and the construction cost of the telescope, and then you get some time on our telescope. 

So that leads to the next question, of course, why did the South Africans want a telescope? And this is one of the more interesting and I think deeply thought out answers to this question, not only in South Africa but in other countries around the world. Mexico is becoming a big powerhouse. These are countries that have typically been known to have had some struggles with their economies. A lot of problems inside the countries in the past. South Africa had its whole apartheid era that it's been recovering from. So why are they doing this for astronomy? Well, they are doing it largely for educational purposes. The power of looking at the sky and trying to understand it and understand our place in it can really fire the imaginations of everybody in the country, particularly the youth who can then go on to study mathematics, engineering, science. They may not become astronomers, but from the perspective of the government, that's okay. They'll contribute to the knowledge and engineering and high tech economy of the country And this is a response to the people who said, why do it now? Why not wait? Wait for South Africa to solve some of its problems. And this is the response. 

And this is back quite a while ago when they were first contemplating this telescope, and now they're in astronomy in a really big way. They, in Australia, are sharing the development and construction of the largest radio telescope, again, a different type of light, radio telescope on Earth. It's going to be a completely revolutionary instrument. Stay tuned, it should be operational in 10 years or so. It's a big deal. It takes a while to build. There it is with some of the local wildlife here. These guys are called springboks, and I wondered why they called them springboks. Well, I found out why because in addition to a regular gait, if they get excited, they spring. They bounce across the felt, this area is called the felt here, in the Karoo, that's the name of the region here. 

They spring. They boing, boing, boing. They spring. It's hilarious I wish I had a movie of them because they are really fun to watch. You could easily sit there for hours just watching these guys. They graze all around the telescope there. This is a big telescope. Here are some pictures, as well as schematics. It's busy. This is a busy picture. 

It's because there's so much stuffed into the dome. They try to make the dome as small as they could. Why spend more money? Again, you want to try to keep things as cheap as possible. So, they built a dome just big enough to hold this behemoth, and hence, because of that, when you're inside the dome, it's hard to see what's going on. So let me give you some perspective here. Let's talk about what this is. This is a walkway up here. That's a railing. I don't think there are any people in this picture, but that railing is about that high. You get a sense of scale. 

So imagine you standing there with a railing about that high, and what I was just pointing out there was that railing to walk along here. This is the primary mirror of the telescope. This is what collects all the light. Remember we talked about bigger collects more light, and the amount of area you have to collect light goes as the square of the diameter? The one on Kitt Peak, the WIYN telescope, the big one, was 3.5 meters. That's pretty big. You saw how big it was compared to the person there. This one is 11 meters. So it's roughly three times larger. Three squared, nine times more light. So this collects about nine times more light than the one in Arizona. 

And it's in the southern hemisphere, so what we can't see from the north of the northern sky we can see in the south from the southern hemisphere. Primary mirror there. It's made up of a bunch of different segments. Because there's a big engineering problem with making a big mirror. They break, they crack, they sag if you make them too big. With the older technologies that were around before the 1990s, couldn't build much bigger than about six meters. Now we're building 10-, 11-, people are working on 20- and 30-meter telescopes. Huge. To again give you a sense of size scale, two meters is about this big. That's two. 

This is 11 and going up from there. And one of the ways to do that is instead of making one giant mirror, this is made in a bunch of segments. And you might be able to see, people in the front might be able to see some of the lines between the segments here. The idea here is that you open this up, light comes down, hits this mirror, and goes up to right here. Now, on the other telescope in Kitt Peak, there was another mirror here. It sent it back down through a hole and then another mirror out to instruments at the side. For reasons based on the design of this mirror, that won't work here. So all of the instruments have to be stuffed up here, way high in the sky, hard to get to, remember that was one of the criteria but we don't have any choice, they got to be up there, there's not a lot of room up there, and you can't have a lot of weight up there. It will go crash. You don't want that to happen. 

So you have to build instruments that are very tightly spec'd, very carefully designed, and very carefully built such that they don't get too big for the space and they don't get too heavy for the load that that can carry. And over here is just a cutout of the thing. This is a diagram looking in as though the side of the dome were not there. You get a little better perspective. There's the primary mirror. This big tower up here is for aligning all those segments. And this is a real picture, there's that tower. So this is looking out at dusk. This is where the instruments all live, and you're looking up at that tower which is used to align that mirror. I mentioned it was cheaper. 

Cheap is good. But it's hard to get something for nothing. So how did they get it cheap? One of the ways they got it cheap and big was they sacrificed some, just some, of the ability to see the entire sky. So remember that was another of our criteria. You want to see the whole sky. Everything you possibly can. This one you can't. You can see about 70% of the sky that you could with a normal telescope. What's abnormal about this? To save money, instead of being able to move the telescope up and down, like this, so if my head were the telescope, most of them can go up and down and sideways. This one can go sideways, but not up and down. 

It's stuck looking like that. Well, that's pretty limiting, right? Well, there are a couple tricks you can play. One is that the sky appears to move. Because of the Earth's rotation, what you're looking at one minute is not the same as what you're looking at the next minute even if you're pointing in the same direction. So the apparent motion of the sky itself will allow you to see more than you think you could just by standing in one spot. And finally, there's another little trick, that big instrument platform up there, it actually moves. So it can move around and give you a little bit of ability to point in different parts of the sky. Well, why not move the whole telescope then? Because it's cheaper to move the instrument platform compared to the whole telescope. You save money that way. So, again, it's a tradeoff. 

You want cheap and you want to be able to see the whole sky. You can't get both. So you trade-off seeing, you give up on seeing a little bit of the sky, about 30%, and you're able to actually afford your telescope. If you couldn't afford it, you wouldn't be doing this at all. So, that's part of the tradeoff that happened with SALT there. In this diagram here, the blue line is just a diagram that shows where in the sky it can actually observe. This direction here is east-west. This is north-south. And this is why you can't get everything. This is like latitude on the Earth. 

It's the equivalent of latitude in the sky, and it should go down to minus 90 and it doesn't. You can only see things inside this region here. Some people call it the cosmic doughnut. And what about east-west? It looks like you can only see part of it. What about in here? You can't see here? That's okay. You just wait for the Earth to spin a little bit and whatever was in the middle there then moves over to one side, and you can still see it. So it's clever. I didn't come up with this idea. It's a great idea. Very clever people. 

It's one of the many things I wish I had come up with that. But no, it wasn't me. But a clever way of getting around some of these problems and saving a lot of money without sacrificing too much. So I talked about the instrument package up there. Remember one of our criteria is you want to be able to get at the instruments. You want to be able to change them easily, fix them, tinkering with them. That's kind of hard when the thing is stuffed up inside this package at the top of the telescope, and it's crammed in there. If anybody has ever opened up the hood on a modern small car, you see how tightly crammed everything is in there. You can hardly access anything. Compare that to a car that's like 50 years old. 

You can almost crawl in the engine compartment. Well, this instrument package is like that small modern car. It's beautifully designed, but oh my goodness, is it tight. You can't easily swap instruments out. But we want to swap instruments out. Different instruments do different things. Solution? Try to build them all into one cohesive hole. This is quite a technical challenge. Most astronomical instruments are not designed this way because it is complex, easy to break, harder to fix, but when you are constrained to do this, the scientists, the designers, the engineers sucked it up and did it, and they made a remarkable instrument. They liken this to the Swiss Army knife with the symbol of Switzerland replaced with the symbol for the next generation of this instrument, but it does many different things. 

This can replace many separate instruments on a more conventional telescope. They're all wrapped in there. The disadvantage is it's hard to get everything to work. The advantage is once you get them all working, you can flip between them in seconds. So we can do an instrument change, that would take half a day or a day on another telescope, in 90 seconds. Just push a button on the computer, the thing reconfigures itself, and off you go. And I've listed just a few of these things up here. Let me start with ones we've already talked about. The spectroscopy, breaking the light up into, let me go down here, the simplest one. It's your basic tool. 

Single object spectroscopy. You've got one star or one galaxy and you just want to get a spectrum of that full stop and then you're done. The spectrum again is breaking the light up into its constituent colors. The natural one, think back to the rainbow from the geyser. That's what we're talking about here. So this is one of the most basic operational modes of a telescope instrument. This has been done for over a hundred years, single object spectroscopy. If you have more than one object that you want to look at one time, the old conventional way to do that was you point at one, then you go point at the other, then you go point at the other. Well, if you need two or three hours of exposure time on each one, you're starting to burn up a lot of time. Then you're colleagues get made because you're hogging the telescope. 

So one of the ways around that is you can try to do multi-object spectroscopy. You look at several things at once. And I'll show you the way this telescope and this instrument does it here in future slides. And then there's a really, really multi-object spectroscopy mode. It's a pretty specialized one. And you can do a combination of imaging and spectroscopy. It gets back to this game we were talking about before. You want a picture and you want the wavelength information at the same time. How do you do it? All these different tricks. We talked about the optical fibers as one of them. 

We talked about the WHAM telescope that would look at just one line and take a picture. This is kind of in between those two. It's a neat technology. I'll show it to you here in a second, this is just basic picture taking. This polar imagery looks at polarized light. The best every day analogy? Polarized sunglasses. It utilizes the fact that light has different orientations. And in sunglasses, the reason they work, the polarized sunglasses, is because light that's reflected off the ground is preferentially in one kind of orientation, the sunglasses block that. You get rid of the glare, and you're happy. This contains a lot of information about the objects that are out there. 

So it's of great utility to astronomers. There is quite a mouthful. Spectropolarimetry. You look at polarized light and break it up into its constituent colors. Oh my goodness, that's a mouthful, and that's a hard thing to do. I have never tried this. And then, oh my gosh, you could try imaging spectropolarimetry, and that, you notice, we labeled with a corkscrew here. And then to really complicate things, you can do it both simultaneously. Visible light, which is light we can see with our eyes, as well as near infrared light, which is a little bit too red for our eyes to see. That is coming. 

So, who's the genius who put all this stuff together? And here he is. He is local here. His name is Ken Nordsieck. He's a UW-Madison astronomer. And this is in the control room of the SALT telescope, Southern African Large Telescope. It's way out in the middle of nowhere, and to keep your sanity, everybody there has to have a bit of a sense of humor. This is just one example of that. And this is an instrument configuration interface on the computer, and I was down there with him. We were trying to get the instrument operational. It takes a long time to work out all the bugs on this or any other instrument. 

It's working pretty well. There are a few modes that we haven't finished yet, but it's generally working pretty well. So I mentioned there was this other way, actually there are a couple other ways, of trying to get as much as you can of what's both the picture of the sky and the color information. One is you can just take narrow slices of color. Take a picture in one narrow slice, take a picture in another narrow slice, take a picture in a third narrow slice, or even a fourth and fifth, and then look at them either independently or added up here. And what's shown here is this technique where the colors here refer to, in most cases, specific elements. This is hydrogen alpha. This is the same thing that the WHAM, Wisconsin Hydrogen Alpha Mapper, it's the same element, it's the same spectral line, it's the same color, but it's just taken with a different telescope. This is sulfur. And the other color here is a bunch of colors added together, and you can make this color image here. 

This is off of the SALT telescope, and it's a gas cloud around a dying star. So people can study the structure of the cloud in these different elements, and you can see, just by looking at the colors, there's more of some elements in some places than there are others. That tells you something about how this cloud is structured, and then you can infer how it was formed and what's going to happen to it. Here's the other one. This is kind of the neat one. It's sort of like the WHAM telescope in Chile, the Wisconsin H Alpha Mapper. Remember, we said it just took a picture of the sky at one particular wavelength, one particular color that was tuned to this hydrogen alpha line, this particular line of hydrogen. And what they're doing, this big survey of the sky, that's good enough. They're all set with that. But what if you wanted to look at more than just hydrogen alpha? Or what if you wanted to look at hydrogen alpha that was moving? Because moving things will change the colors slightly. 

What are you going to do then? In the case of WHAM, you have some adjustment to it but not a lot. Part of this instrument on the Southern African Large Telescope allows you to do the thing that WHAM does, take pictures at individual slices of colors, but at very fine steps. So, it's like having the spectrograph that spreads them all out and the picture-taking capability. The cost is time. It takes you more observing time to do that. I mentioned, and we're going to be wrapping up here pretty soon, I'm just going to go through a few other of the interesting modes in this instrument. I mentioned that there was this capability of doing multi-object spectroscopy. Well, how do you do that? One of the ways you can do it is by taking a piece of carbon fiber, which is shown here, you can see somebody's holding it here for scale, and you punch a bunch of holes in it. Actually, a precision laser cutter does this, not a person with an ice pick sitting there. It has to be done very precisely. 

Believe me, you have these things off by a slight amount and you mess with your data. The idea of this is that if you know where all your objects are in the sky, you can program the laser cutter to drill little holes or little slits on every one of those objects. And in each one, light goes down into the instrument and it can be broken up into its colors. You can do spectroscopy on it.  Here's a schematic of it. That last one was a real physical mask. This is a computer display. What's shown here is a galaxy. There's another one down there. And all these little things here are little holes. 

This is a design for the mask. This is a computer design to build one of these masks, and what we do is just decide where on this galaxy we want to put it. So that one right there, for example, will let light just from that area, and the light will get spread out in this direction. So the rainbow of colors will go this way. That's why you can't have them overlapping. And then this one, you have another one. There's another rainbow of colors there. And here there's another rainbow of colors. And here there's another one. So you can look at the spectra, the distribution of colors, at all these different positions on any of these galaxies. 

Multi-object, more than one at a time. To try to do this in the old traditional way, you look at one spot, you look at another spot, you look at another spot, good grief, you'll be there forever. These are what the raw data look like. This comes right off the instrument. Each of these little bands is from one of those little holes, those little slits. So think back, in fact we can go back here, see all those little slits that were here. Each one of these will spread light out this way, perpendicular to where the slit is, and this next one shows that light spread out. So each of these bands here is the spread out light from one of those little slits. And there's a lot in here. Whoops, I wasn't supposed to do that! Come on. 

There we go. So, we are now seeing light coming through each of those slitlets. The vertical lines are from the night sky. The night sky glows. It produces a lot of light. If you're ever out on a dark site, get dark adapted, ever wonder why you can still see your hand? It's starlight, true, but there's also glowing from the atmosphere. The atmosphere itself glows, and that's what these things are, the vertical lines. The horizontal lines are the ones we're interested in. Those are the objects in the sky. Those are the celestial targets whose light is being spread out. 

So this is what the data look like that actually come off that multi-object spectroscopy capability, all right. And I just wanted to show a couple little travel log pictures here as we finish up here at the end. This is the Great Karoo. It's an arid region of South Africa. This is what it looks like. This is after a night of observing on the SALT telescope, Southern African Large Telescope, and I just felt like going out and taking some pictures. It was a beautiful dawn out there. You might think, well, if you escape Wisconsin and go to Africa, you're going to be able to escape the snow. But no, alas. Nothing like we've had here in the last week, nothing like the ice that we've had around here recently, but you do actually get snow occasionally in the deserts of South Africa. 

And here's proof in the pudding. We were down there, obviously, in the winter, and this is, over here on the right, this is the hostel. This is where everybody stays. And then you drive up to the telescope to utilize it. There's some future work coming on this telescope. I mentioned this briefly that there would be a joint visible light infrared light capability. So all of that myriad of capabilities that I showed in the Swiss Army knife diagram, that was for visible light, all of those capabilities are coming in infrared light. In fact, the leader of this project is in the audience tonight, so afterward, when the talk is done, we can chat with her if you'd like and hear more about that. And I just have one very complex looking plot. I won't spend a lot of time on this, but just to show you briefly here. 

It's hard to do this. So, pay attention just mostly to the blue lines here. This, again, is color, but this is now in the infrared. This is blue. Blue. That's actually redder than our eyes can see. Remember, we're in infrared, beyond the red that our eyes can see. So this is, down here on the left, is the blue side of infrared, and then you get to redder and redder as you go out to the right here. And all of these spikes in here are bright skylines. I told the sky glows. 

It really, really glows in the infrared, and it also is not very transmissive. The blue line here shows how much the atmosphere transmits. You want it to transmit a lot. Some regions it doesn't transmit much at all. So it's actually a lot harder to do astronomy there. And only brave people will try to build instruments here. It can be done. It's successful, but it's hard to do. Now, we're going to end where we began. What makes a perfect telescope? I just want to put this up here. 

These were some of the criteria again. There is no perfect telescope. You can't have a perfect telescope. You can't combine all of these different features in one telescope. And even if you could, even if you could get all of them except... You would still have this one. You want vast amounts of observing time for everyone. You can't do that with one telescope. So even if we could get everything else into a single telescope, there are too many astronomers clamoring to use it, and therefore, we would need more than one even with that. But the flip side of this is yes you have to have more than one telescope, yes, Wisconsin has shares in telescopes in Arizona, has a telescope in Chile, has a share of a telescope in South Africa, utilizes national and international facilities and radio and other bands of light, both on the Earth and in space, all these resources, yes we have to have all these things, but the advantage is that then you can tailor them like we've talked about. 

They can have different instruments. They have different strengths and weaknesses. The Arizona site had excellent native image quality. The Southern African site had this very extensive suite of instruments so you can easily change between them. So it allows you a lot of flexibility and allows you some tailoring. So that, basically, is why Wisconsin astronomers have telescopes spread throughout the world and also on the ground and in space. And with that, thank you very much, and I look forward to seeing everybody next time here at Space Place when I'm back. [APPLAUSE]