1. Astronomy: The Visible and Invisible Universe
I am an astronomer at the National Radio Astronomy Observatory.
First -- and I know you’re all thinking -- what the heck is radio astronomy?
Well, some people study the Universe in visible light (the “what you see is what you get” astronomer). Other people study the Universe in light that you can’t see (like ultraviolet light, infrared light, and the longest waves, which are called radio waves).
So, radio isn’t sound, it’s light. And just like fiber optic cables send signals via light waves that your computer can turn into sound and pictures, on Earth we use radio waves to “carry” signals. But, radio is actually a natural form of light.
Lots of things in space also give off natural radio waves, and we use special telescopes to study these objects.
If you want to make your own radio transmitter, tune an AM radio until you only get slight static. Then tap a nickel to a 9-volt battery. The “popping” sound you here are radio waves from your little transmitter.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

2. A light wave is a light wave, no matter how long...
Just to help you understand about radio and light. This shows that visible light, and microwaves, and X-rays, and radio waves, are really all the same thing. The only difference is how long the waves are.
If you’re very, very energetic, you’re called a gamma ray (it takes a lot of energy to get the waves to be that close together. Think of it as squishing together a spring. The smaller the spring, the more energy it takes to compress it.
To get gamma rays, you need some of the most energetic events in the Universe. Exploding stars, massive black holes, and other things create gamma rays. They’re smaller than some atomic nuclei.
You all have had X-rays, and they’re pretty energetic too. So energetic that they can pass right through skin (but not so easily through bone).
Visible light -- the stuff you see -- is made in pretty energetic places too (like burning wood, or when electricity runs through a wire). The different colors that you see are simply light waves of difference length.
When you get all the way down to the longest wave, you have radio waves. Which can be made by some relatively cool objects. And that’s very good when you’re studying space -- because not everything is lit up by a burning star.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

3. I suppose the most obvious thing that you notice when you look to the sky is the sun.
But, even though the sun is our nearest star, and it is so well studied, we still have much to learn about how it was formed, what is happening on the inside, and what will happen to it in several billion years.
This picture shows that even though we think of the sun as a very constant object, it is actually very violent, and changing constantly. These solar flares, born of the Sun’s immense magnetic fields, can cause serious problems on Earth for communications and electronics.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

4. Here are our neighbors in the solar system
Here are our neighbors in the solar system. From the nearest to the sun, moving out. Though the planets are not to scale, you do see the vast difference in each of them. From the inner “rocky” planets, to the gas giants, to Pluto, which some astronomers don’t even consider a planet at all, but a lost member of the Kuiper Belt -- a region of ice and rock beyond the orbit of the “true” planets.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

5. Home sweet home…
We should point out that we are now able to learn more about our Earth because of astronomy and space exploration. The Earth-orbiting satellites that we use for navigation, defense, television, radio, and on and on were actually first envisioned by science fiction author Arthur C. Clarke. In his book, “Islands in the Sky” Clarke was the first to predict that satellites at 22,700 miles above the Earth could allow for true global communications.
Of course, at the time this book was published, there weren’t sophisticated computers, so Clarke assumed that satellites would have to be floating “islands” with lots of people constantly working to replace all the vacuum tubes that would burn out.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

6. Some Solar System Neighbors
Very near to Earth are some of the ‘leftovers’ from the formation of the solar system. Here we see two of these kind of objects. The first is that of Comet Hyakutake -- perhaps once a member of the Kuiper Belt. The next is something called a NEA -- a near-Earth asteroid. This particular one is shaped like a dog bone.
By studying these objects, astronomers are able to learn a lot about what the solar system was like just when the planets were forming, over 4 and a half billion years ago.
They also remind us that the Earth is part of a very “crowded” solar system. And sometimes traffic accidents do happen…
Doggie Treat
Asteroid
Comet Hyakutake
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

7. What happens when your neighbors get too close...
Meteor Crater, Arizona
Only 50,000 years old
Chicxulub, Mexico
65 million years old
(probably killed the dinosaurs)
Here are just two examples of what happens when these solar system leftovers get caught up in Earth’s gravity.
The colorful image on the left is a large depression off the coast of Mexico. It is a massive crater from an asteroid that hit Earth about 65 million years ago -- the same time that the dinosaurs died out. It might be the “smoking gun” of why the dinosaurs died. There is even evidence that other mass extinctions in Earth’s history correspond to massive asteroid impacts.
To the right is a relatively small crater in Arizona. This one hit only 50,000 years ago -- which “astronomically speaking” is very little time.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

8. Venus -- UV to Radio
Before moving too far from “home” I wanted to point out a few interesting things about other planets in our solar system.
Here you see two very different pictures of the same object (or at least a portion of that object).
On the left, this purple egg thing, is actually an ultraviolet picture of the planet Venus -- the brightest planet in the sky. But, what you’re actually seeing is its thick, toxic, and acidic atmosphere.
For many years, astronomers on Earth thought that there might be a world filled with tropical plants and other life forms under this shroud of clouds. Later studies of the atmosphere and then pictures of the surface revealed a very different place. Today we know that Venus is a hot, hostile planet.
The second image is actually a picture of the surface of Venus made by the NRAO’s Green Bank Telescope -- with a little help from the Aricibo telescope in Puerto Rico. Astronomers “bounced” a radar pulse off the surface. So we actually get to see the surface without leaving Earth.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

9. Mars -- New Views
Since there is continuing speculation on whether or not life ever evolved on Mars, I wanted to show two pictures that demonstrate that now there is at least a little water locked up on its surface.
The first is the image of the whole planet, the second is the northern polar ice cap, composed mostly of water. The cap is roughly 680 miles across.
With studies on Earth that show that bacteria can live in some pretty hostile places -- like inside the rocks in Antarctica or inside boiling hot springs, it’s not unreasonable to think that there might yet be a little life hiding out somewhere on Mars. But, as yet, none has ever been detected.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

10. What’s that little speck of dust?
As we leave our solar system, I wanted to show one last picture. Can anyone here guess what the little speck of dust that you see in this light beam is?
This is the planet Earth -- it is a picture taken by the Voyager spacecraft as it traveled toward the edge of our solar system.
Though Earth may seem like a very big place, it actually contains less than 1-percent of the mass in our solar system.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

11. What do you see in the sky at Green Bank?
As you look out from the solar system, you see some rather peculiar stuff. Here’s an interesting picture that was made of the sky over Green Bank, West Virginia.
The first thing you’ll notice is that there are a number of telescopes on the ground. My question is, what are those things that you see in the sky?
They sure look like stars that you see in the evening sky (with a few other blotches thrown in for good measure). But what you’re actually seeing are radio sources. Every dot, smudge, and bubble in the sky is actually something that emits radio waves. Some are galaxies, some are clouds of dust and gas, others are even stranger things. But, this is what your sky would look like if your eyes could see radio waves.
What that should be telling you is that there are more things in the Universe than can be seen with the eye, or even with the biggest optical telescopes.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

12. A Galaxy of Stars…
As you may know, our solar system is one of many billions of other stars all clumped together in the Milky Way Galaxy. Here’s a picture of another galaxy -- one relatively close to our own, called the Andromeda Galaxy.
The Milky Way was not named after the candy bar. If you go outside on a very clear night, in a very dark area, and look up at the sky, you’ll see a hazy band of light stretching across the sky. Ancient mythology called it the milk of the Goddess Hera shooting out across the cosmos, which is why we call the Galaxy the “Milky Way.” What you’re really seeing are the stars in toward the center of your own galaxy -- looking at it edge-on. Years ago, nearly everyone could identify the Milky Way in the night sky, but now with so many lights from cities and homes, it’s getting harder and harder to see the Milky Way with the naked eye. Many people in the world, in fact, have never seen the light of their own Galaxy, which was as common a feature as the Moon to people years ago.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

13. Same Space -- Different Light
Radio
Infrared
Believe it or not… these pictures are of the exact same thing. What you’re seeing is what the Milky Way looks like in different wavelengths of light. You notice that in the optical image… you see a lot of dust. That an important point, because we can’t see into the center of our own Galaxy in optical light. There’s too much dust in the way.
Radio waves, however, are able to penetrate the dust, and we can detect them here on Earth. That allows us to see what the inside of our own Galaxy looks like.
Optical
X-ray
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

14. Here’s an even more detailed picture of the center of the Milky Way, seen in radio light.
Notice all the interesting bumps and lines. None of these can been seen in optical light. And, right here in the center, in an area called Sagittarius A, is a very, very bright area. That is the very center of the Galaxy, and there’s something there that creating a massive amount of energy.
What we think it is, is a Black Hole. This is the most dense, heaviest object in the Universe. It’s so heavy, that it bends space itself. It has a gravity field that is so strong that light cannot escape.
We cannot -- at least with our current understanding of nature -- ever see into a black hole, but what we can do is study the energy that surrounds this area to learn what it is and what it’s doing to the galaxy.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

15. There are billions of other interesting galaxies in the universe
There are billions of other interesting galaxies in the universe. Some are even doing some unexpected things. Here are -- what once was -- two separate galaxies. You can see that they are colliding, wrapping around each other… sort of like a dance. This particular image is called the “Antennae” because it looks like an intergalactic antenna.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

16. Galaxies also do some interesting things
Galaxies also do some interesting things. The image you have here is something called a “radio galaxy” -- that is, a galaxy that is VERY active at radio wavelengths. The very bright spot in the center is most likely a very massive black hole, and as it’s gobbling up entire stars’ worth of matter and then spewing out these long, powerful radio jets, many light-years into space.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

17. Orion Nebula -- Hubble and VLA/GBT
So… where do you get stars? Right here you can see an interstellar cloud of dust and gas. We call it the Orion Nebula. It’s in the constellation Orion, and you can actually see it very easily from Earth.
This is a very typical area for making stars. You get a lot of dust and gas in one area, and when you get enough gravity, the dust starts to condense -- or collapse. As this stuff collapses, it starts to spin and collect into clumps. Just like a skater pulling in her arms, the more mass closer to the center of gravity, the faster the spin.
If you get enough matter in the center, the hydrogen atoms begin to fuse and form helium atoms, then a star is born. The rest of the stuff in this proto-planetary disk is swept up by the larger clumps, eventually forming planets. Some small and rocky, like Earth, others massive and gassy -- like John Madden -- or Jupiter.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

18. All good things must come to an end…
Well, we talked about where and how stars are formed. But all good things must come to an end. For some stars -- something about as big as our own Sun -- that usually means a brief period of growing very big and very hot, something called a Red Giant. Of course, we have many billions of years until that happens. After that, the outer layers of the star shoot off into space, and you’re left with a white dwarf star.
If a star is bigger… you might get a really explosive ending and have a supernova. This is a spectacular and cataclysmic event. What’s left is a shell -- like the one you see here. Inside, often, there will be a pulsar -- the lighthouse of the Universe.
And finally, if the star is REALLY bigger -- hundreds of times bigger than our Sun, it collapses into a black hole. As mentioned, we can’t see the black hole directly, but we can infer where it’s at and what it’s doing.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

19. The Wanderer…
This graphic shows one such black hole, as it goes roaming around the Milky Way Galaxy. The black hole is on the top of the galactic plane, and that little yellow dot is you and me.
Just goes to show you never know who’s going to drop by for a visit.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

20. Other weird stuff... Dark Matter Gamma Ray Bursts SETI
Talking about the Universe… I could be here for the next ten years and not even start to cover all that’s going on. But, to leave you with this thought… there are weirder things going on in the Cosmos than I or other scientists can possibly explain right now -- though we’re trying.
What is Dark Matter -- everything that we see is only a small fraction of what really makes up the Universe. In fact -- matter as we know it, that is matter made out of atoms -- is only a small fraction of the mass in the Universe. What’s the rest? No one knows…
What are Gamma Ray Bursts -- The second most powerful thing in the Universe after the Big Bang are Gamma Ray Bursts. They may be happening at the edge of the known Universe. They may be much closer. And exactly what they are remains a mystery.
SETI -- Are we alone? To date, there has never been a message received from outer space, but there are scientists who still keep listening.
Any questions?
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.