365daysDate: September 25, 2009

Title: Modern Telescopes and Observation Techniques


Podcaster: Demi, Mark Webb, and Dr. Mark Subbarao of the Adler Planetarium

Organization: Adler Planetarium

Description: From the Hubble Space Telescope to the Sloan Digital Sky Survey, how are we looking at the night sky today?

Bio: The Adler Planetarium — America’s First Planetarium — was founded in 1930 by Chicago business leader Max Adler. The museum is home to three full-size theaters, including the all-digital projection Definiti® Space Theater, the Sky Theater which utilizes a Zeiss optical projector, and the Universe 3D Theater. It is also home to one of the world’s most important antique instrument collections. The Adler is a recognized leader in science education, with a focus on inspiring young people, particularly women and minorities, to pursue careers in science.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the National Radio Astronomy Observatory, celebrating Five Decades of Training Young Scientists through summer programs. Explore the hidden universe in radio at


Demi: Welcome to a special edition of the Adler Planetarium’s bi-weekly podcast, Adler Night and Day. The Adler Night and Day podcast provides listeners with a glimpse of what they can see in the night sky, as well as updates on recent solar weather and riveting conversation. For the 365 days of Astronomy, daily podcast of the IYA, we’ll be focusing on the riveting conversation. Without further ado, I’m your host Demi…

Mark Webb: And I’m Mark, and today we’ll be joined on Adler Night and Day by Dr. Mark Subbarao of the Adler Planetarium. Welcome, Mark.

Mark Subbarao: Thanks for having me.

Mark W: Today we’re going to talk about modern observation techniques. We’ve come a long way since Galileo’s telescope 400 years ago. What are the major advances in optical telescopes, cause that’s what most people think of when they think of telescopes, what are the major advances over those 400 years?

Mark S: Well, of course, like any technology, in 400 years a lot of stuff happens. But with telescopes, I think the main thing really, is that telescopes have gotten bigger. And when you go bigger that enables you to do a lot more, so people think about telescope and they think about magnification, and they think about making tiny things big, and that’s not really what a telescope buys you. The most important things are that they let you see things that are really faint. So, with a big, big telescope we collect more light and we can see things that are much fainter. And what that means is when something is intrinsically real faint or, more than likely, very far away, cause our universe is incredibly big, we can see things that are farther away because they’ll appear fainter. So, by making bigger and bigger telescopes we’re able to see fainter objects and see deeper into the universe. There’s another important thing that telescopes buy you and that’s the ability to see detail. So one way you can see more and more detail is by having bigger and bigger telescopes. There’s actually a mathematical equation that says, as the telescope gets bigger I can make out finer and finer details. If I wanna understand, say a galaxy and make out structures in that galaxy the problem is that Earth’s atmosphere actually prevents that from happening it blurs out the light and so one big advance is that we’ve made with the Hubble telescope and with other space based observatories is to go above the Earth’s atmosphere and that actually allows us to see not only very faint things but actually make them out in more and more detail.

Mark W: Sharper image.

Demi: Everyone is pretty familiar with the optical telescope, what are some other ways we’re observing the sky?

Mark S: Well, well that’s a really interesting question. So, um… astronomy is kind of a difficult thing. It’s a crazy endeavor if you really think about it. We don’t have galaxies in our lab. We can’t, you know, make black holes, even though people are worried about that.

Demi and Mark W: Laugh

Mark S: But what we can do, we can observe distant stuff, we can look at it’s light. And to do that, ya know we’re pretty much… we can only study light that we can detect here on Earth. And that’s a real challenge. Um, so one of the ways that we’ve advanced our knowledge is by looking at different types of knowledge. So it turns out that there isn’t just the type of light we can see. Light comes in different wavelengths part of that we observe in different colors but we can go to wavelengths longer than the longest wavelengths that we can see which is red, we can look into the infrared, and we can look into radio waves. And we can look into wavelengths that are shorter than purple, and we look into ultraviolet and x-rays and gamma rays and doing that we’ve been able to uncover a whole mess of interesting things. Now interestingly, there are a bunch of observations that are just taking place so going into different wavelengths of light, we call that multi-wavelength astronomy we’re just beginning to use things other than light to study the Universe and this is something that’s beginning to be called multi-messenger astronomy. So, it turns out that other stuff comes out of stars and galaxies, they’re particles. And we can actually detect these particles so, um… when we see these particles like protons and electrons, they will actually fly through space and impact our atmosphere. We’ve known about that since the beginning of the century but we’ve never been able to do astronomy with it. One of the reasons why is that these particles are charged particles, they pass though magnetic fields and they’re curved on their path to Earth. So we don’t know where they came from, if you don’t know where they came from you can’t sort of map out the skies. But by looking at extremely high-energy particles, incredibly high-energy particles, particles… a proton that has as much energy as fast ball by a major league pitcher. These guys are actually so energetic that they punch though magnetic fields and go relatively straight. So we’re starting to map those out in the sky. There’s a project in Argentina called the Pierre Auger Observatory that’s doing that. The problem is that they’re very rare. So these particles that we need to do this type of measurement hit the Earth at a rate of one every square kilometer, so that’s a big area. One every square kilometer every century.

Demi: Wow.

Mark S: So, yah… imagine trying to do that study. Say you’re a graduate student, you build your square kilometer detector and you wait and you might… one point in the century you could write a paper, right… so it’s not going to work. But what they done is, um… actually built a huge detector, bigger than the state of New Hampshire, so you have many, many square kilometers. And they’ve been able to detect many some objects and trace them back. It looks like they’re coming from black holes in our galaxy.

Mark W: Oh, wow… that’s pretty interesting

Demi: Interesting.

Mark S: It’s actually a pretty major discovery. Um, and there’s other types of measurements that are just starting to be important. Um, there’s, so… cosmic rays are sort of normal types of particles. Another type of particle we could hope to detect are actually neutrinos. Neutrinos are these extremely light particles that seem to have a little bit of mass but very little. They travel very close to the speed of light, but they don’t interact with anything. So, cosmic rays are coming down, they’re hitting us on the Earth all the time. There is like one passing through you every second or so. But they’re quadrillions of neutrinos passing through you every second. And they not only pass through you, they pass through the entire Earth, most of the time without doing anything. But if we build a detector big enough, occasionally, these neutrinos interact with something and we can figure out where they’re coming from. And so there’s a big experiment going on in Antarctica called Ice Cube, which is actually using the ice as a detector. Because ice, if you go down deep enough, is very clear. And with that we’re hoping to map out neutrinos along the sky. Now they’re making maps… so far they don’t look like anything.

Mark W: Uh-huh…

Mark S: So these new multi-messenger things are really on the edge of what’s possible. And the last kind of new kind of astronomy, the astronomy of the next century, is called something like gravitational wave astrophysics. And this is really crazy stuff and it’s a consequence of Einstein’s theory of general relativity but when you have certain types of gravitational interactions, particularly black holes, a binary pair of black holes coalesce with each other. That’ll actually change the nature of space-time. It will actually send ripples throughout the entire Universe. And what will happen is that space will actually change. Like you and me, if a black hole goes off, you know, across the universe and then this ripple will propagate and for a while you and me will get closer and smaller by a little bit. We can actually measure that using lasers and so there’s an experiment called LIGO, now. Um… there are bigger experiments planned putting actually constellations of satellites in space that would pass lasers between them to try to measure this changing of the nature of space.

Demi: Wow, that’s really interesting!

Mark W: That’s really cool!

Demi: You do a lot of work with visualizations, what exactly is that and what are you trying to learn.

Mark S: Visualization is actually trying to take the data we get and make images and pictures and things that we can interact with. And I think it’s really important, especially as our ability to collect data has improved so much that it’s much more complex, it’s harder to look at. So, um… for instance, if I’m looking at a map of galaxies, if I haven’t mapped very many it becomes very easy. But when I’ve now created millions of them it become much harder so what we do are ways of presenting um, data in a way that we can sort of understand it better.

Mark W: You mentioned a map of galaxies, you’re also part of the Sloan Digital Sky Survey. What can you tell us about that?

Mark S: Thanks, Mark… it’s the, uh… largest project ever to map the Universe. So what we’ve done, and I’ve worked on it for the last decade, is uh, make a three-dimensional map of the position of nearly a million galaxies and so it took a lot to do that. One in which we do that is pick out what galaxies we wanted to map. And so to use that we sort of built what at the time was the best digital camera in the world. And then once we’ve done that we’ve actually determined their distances, um… by looking at the spectra and measuring something called the red shift. That’s the part of the project that I worked on, was writing the software to do that. The result is that if we know where a galaxy is and also how far away it is, we can place it in the three-dimensions, and the resulting three-dimensional map tells us a lot about the universe. What we see is what we’re now calling the cosmic web of the structure. These filamentary structures that are joined together into clusters and that this, the nature of this structure actually, you know, as well as a big sort of map of our universe and letting us know what our universe looks like, but the nature of how clustered the Universe is let’s us know about what it’s made of what it’s future will be, and pretty profound questions like that.

Mark W: That’s pretty exciting. Well, Mark, thanks for joining us on this special episode of Adler Night and Day.

Demi: Thank you

Mark S: My pleasure.

Mark W: I’d also like to thank the listeners of the 365 Days of Astronomy podcast. To listen to full episodes of Adler Night and Day, please visit

End of podcast:

365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by the New Media Working Group of the International Year of Astronomy 2009. Audio post-production by Preston Gibson. Bandwidth donated by and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at or email us at Until tomorrow…goodbye.