You might know the name "Hubble" because of the Hubble Space Telescope. But this phenomenal observatory was named after one of the most influential astronomers in modern history. Hubble discovered that galaxies are speeding away from us in all directions, leading to our current understanding of an expanding Universe. Let's learn about the man behind the telescope.

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Launching a rocket into space requires a big effort on the ground. Space agencies have built up huge infrastructures to store, prepare and launch rockets. Let's take a look at what's involved on the ground at a place like Cape Canaveral. What happens before, during and after a launch.

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Every now and then, the Moon destroys the Sun. Okay, not destroys, covers. Well, not really covers, but from here on Earth, sitting inside the shadow of the Moon, that's what it sure looks like. These events are called eclipses, or more precisely, transits and occultations. They occur whenever one object passes in front of another from a 3rd perspective. They're beautiful and exciting, and deliver a tremendous amount of science as well.

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Astronomers have been searching for the mysterious Planet X for hundreds of years. It was the search for a theoretical planet beyond Uranus that turned up Neptune, and then again for Pluto. And even now there are some astronomers who think there's a more distant planet out there. Oh, and there are a bunch of pseudoscience cranks trying to freak people out about the end of the world. Don't worry, we'll make time for them too, but first let's start with some real science.

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Imagine an object with the mass of the Sun, crushed down to the size of Manhattan. Now set that object spinning hundreds of times a second, blasting out powerful beams of radiation like a lighthouse. That's a pulsar, one of the most exotic objects in the Universe.

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Did you know there are 88 constellations in the night sky? Let's learn about the constellations and other star formations, their history, their connection to the zodiac, and how to find some of them.

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This week we're going to talk about famous stars. But not those boring human ones you read about in People magazine. No, we're talking about those hot balls of plasma across the distant Universe. The close ones, the bright ones, the massive ones, the giant ones. Let's get to know some famous stars.

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We think we live near an average star, but that's not the case at all. Compared to most stars in the Universe, the Sun is a giant! Let's look at the small end of the stellar spectrum, to stars with a fraction of the size and mass of our own Sun. There are many ways that a star can get small, and they lead dramatically different lives and deaths.

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This week we step away from our regular programming to bring you a live show from Dragon*Con in Atlanta. Pamela shares the stage with SETI researcher Seth Shostak. Together they discuss the technology and science of searching for intelligence, And answer questions from the audience.

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If you live in a city, it's possible that you've never seen the Milky Way with your own eyes. To really appreciate everything the night skies have to offer, you've got to get out of the city, away from the lights, where the skies are really dark. But those places are getting harder and harder to find. Let's talk about what you can do to find dark skies, fight to make the skies darker, and how to make the most of wherever you live.

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Did you know that our Solar System is a rarity with its single star. Astronomers believe that most star systems out there actually contain 2 or more stars ? imagine seeing a sky with 4 suns. These binary and multiple star systems are a great target for new astronomers, and the dynamics of multiple stars keep astrophysicists busy too. Let's take a look at what it would be like to live on Tatooine.

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Take a quick breath. There, that's what we're going to talk about today ? the atmosphere. And not just the Earth's familiar atmosphere, but the strange, exotic and deadly atmospheres we find in the Solar System and surrounding extrasolar planets.

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We've explained how to get into astronomy and buy your first telescope. Now we're going to take things to the next level and get you drooling about bigger and better telescopes. If you're serious about astronomy, what kinds of telescopes will give you the best bang for big bucks?

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It's been more than 40 years since humans first set foot on the Moon. But plans are in place to return humans to the surface of the Moon, and maybe even to asteroids and the planet Mars. New rockets, landers and flight technology are all under development. Humans are pushing out into space again, and this time we're going to stay. Let's take a look at NASA's new Constellation Program. What's been developed so far, and what's coming up.

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Astronomy is one of the scientific fields that have been completely shaken up by new media. The Internet has enabled communication between researchers in a dramatic new way, creating new collaborations, removing obstacles, and drawing in an army of enthusiastic volunteers to help with research. Let's take a look at how new media is helping change astronomy, and how you can get involved.

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For those non-scientists trying to get their original ideas accepted by the scientific community, you've got to have thick skin. It might seem like there's a vast conspiracy, or a general attitude that drives away original, but unorthodox ideas. But that's not true, the reality is that great ideas in science come from everywhere, even amateurs. In this episode we'll help you understand what scientists will be looking for, and the best ways to be taken seriously.

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Have you ever wondered how astronomers do their research? How do they go from idea or question, to gathering their data, to publishing the research. What are all the hoops they have to jump through, the paperwork to fill out, and the cool toys they get to use along the way?

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In science fiction it's easy to hop into your spaceship and blast off for other stars. But the true distances between stars, and the limits of relativity make interstellar travel almost impossible with our current technology. What would it really take to travel from star to star, exploring the galaxy?

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What will we eventually be able to see on extrasolar planets? What does an infinite Universe mean? And what's down there, inside a black hole? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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If you want to travel into the Solar System, you have to get off the Earth. Traditionally, that meant blasting off in a rocket. But there's another strategy for escaping the Earth's gravity. Climb to the top of an extremely tall tower, and just jump away. That's the idea behind space elevators. Theoretically possible, but practically unfeasible, space elevators have gotten new life thanks to new, super strong materials.

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Why was there a difference between the amount of matter and antimatter at the beginning of the Universe? Mathematics lets us travel faster than light speed, so why can't we? And are there stars forming around black holes? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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We know there's life in the Universe. We see it all around us here on Earth. But is there life anywhere else? By studying the extremes that life can take here on Earth, scientists are learning just how hardy and adaptable life can really be. And if you consider other ways that life might function, the options open up considerably. This week we'll discuss the study of life - extreme life here on Earth, and the possibility of finding life on other worlds.

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Why are black holes black? Can a huge mass of humanity make the Earth wobble? And what's so bad about space pollution anyway? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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The surface of the Earth feels solid under your feet, but you're actually standing on a plate of the Earth's crust. And that plate is slowly shifting across the surface of the Earth. Over geologic timescales, plate tectonics has totally resurfaced our planet, bringing continents together, and tearing them apart. We know we have plate tectonics here on Earth, but what about other worlds?

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Will robots be able to avoid the heat death of the Universe? Can galaxies orbit each other like binary stars? And what are the dangers of space radiation to astronauts on the Moon? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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You're familiar with volcanoes, eruptive vents where hot magma escapes the Earth's interior ? sometimes with disastrous effects. But did you know that volcanoes have shaped many of the planets and moons in the Solar System, not just our own Earth? And just in the last few years astronomers have discovered there are cold volcanoes on some of the icy objects in the outer solar system.

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How can you get a Galileoscope of your very own? What happens to time inside a black hole? And what exactly is energy anyway? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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One of the most amazing aspects of quantum mechanics is quantum entanglement. This is the strange behavior where particles can become entangled, so they're somehow connected to one another ? no matter the distance between them. Interact with one particle and the other reacts instantly; even if they're separated by billions of light-years.

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What starting telescope equipment does the Astronomy Cast team suggest? How much energy does a black hole generate? And how do we measure time outside the Earth? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Last week we took a peek into the tiny world of quantum mechanics, and its unintuitive, but very accurate mathematical predictions. And although we all appreciate the physics lesson, you're probably wondering what this all has to do with astronomy. Well, today we bring it all home and explain how quantum mechanics has given astronomers one of the most powerful tools they have to study the nature of the cosmos.

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What would happen if the Moon wasn't tidally locked to the Earth? What happens to all that mass and energy disappearing into a black hole? And how can we explain the space station's crazy orbit? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Quantum mechanics is the study of the very tiny; the nature of reality at the smallest scale. It's a science that defies common sense, and delivers no helpful analogies. And yet it delivers the goods, making scientific predictions with incredible accuracy. Let's look into the history of quantum theory, and then struggle to comprehend its connection to the Universe.

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Are new stars dark until their photons reach the surface? How fast do neutrinos travel? And what?s the story with Hawking Radiation? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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This week we?re going to think big. Bigger than big. We?re going to consider the biggest things in the Universe. If you could pull way back, and examine regions of space billions of light-years across, what would you see? How is the Universe arranged at the largest scale? And more importantly? why?

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How do planets get their atmospheres? What would happen to the Earth if the Moon just disappeared? And what?s that strange glow we see after sunset? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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And now we reach the end of our tour through the electromagnetic spectrum. Last stop: gamma rays. These are the most energetic photons in the Universe, boosted up to incredible energies in the most violent places in the Universe. Gamma rays are tricky to catch, but they can reveal the most dramatic events in the Universe.

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Can our Sun generate a solar flare that would wipe out life on Earth? Has the Large Hadron Collider answered any questions about the Higgs boson? And what would happen if you shined your flashlight out the front window of a spaceship going almost the speed of light? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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If you've ever broken a bone, X-rays are a part of the electromagnetic spectrum. Doctors use X-rays to study the human body, and astronomers use X-rays to study some of the hottest places in the Universe. So let's put on our X-ray specs, and see what we can see.

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Pamela was lucky enough to attend the NorthEast Astronomy Forum, and while she was there she held a live questions show. And now you get to join in an hear the interesting questions, and Pamela's interesting answers. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Our next visit in this tour through the electromagnetic spectrum is the ultraviolet. You can't see it, but anyone who's spent a day out in the hot sun without sunblock has sure experienced its effects. Ultraviolet radiation is associated with the birth of stars and some of the hottest places in the Universe.

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Optical astronomy; now this is the kind of astronomy a human being was born to do. In fact, until the last century, this was the only kind of astronomy anybody ever did. Now we've got the whole electromagnetic spectrum to explore, but our heart still belongs to optical astronomy. Of course, with bigger telescopes, better optics and more sensitive detectors, even optical astronomy has come a long way.

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If there was enough mass to cause a big crunch, would inflation go backwards too? How do spacecraft know that hydrogen is bonded to water? And why can't we see everything that's ever fallen into a black hole? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Today we continue our unofficial tour through the electromagnetic spectrum, stopping at the infrared spectrum - you feel it as heat. This section of the spectrum gives us our only clear view through dusty material to see newly forming planetary systems and shrouded supermassive black holes. And infrared lets us look out to the most distant regions of the observable universe, when the first building blocks of galaxies came together.

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Last week we examined the largest wavelength in the electromagnetic spectrum: radio. This week we get a little smaller? but not too small! And look at the next step in the spectrum, the submillimeter. Astronomers have only recently began exploiting this tiny slice of the spectrum, but the payoff has been huge.

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This week we wonder if you can made a black hole by accelerating a mass, but then can you un-make it again? Will the Earth ever be tidally locked to the Sun? And can dark matter crush an unsuspecting space ship? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Astronomers are very resourceful, when it comes to light, they use the whole spectrum - from radio to gamma rays. We see in visible light, but that's just a tiny portion of the spectrum. Today we're going to celebrate the other end of the spectrum; the radio end, where photons really stretch out their wavelengths.

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This week we wonder if the Universe is going to collapse and then expand again, how satellites can have such different velocities, and the size of the observable Universe. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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When it comes to telescopes, bigger is better. But bigger is more expensive. Way more expensive. To keep the costs reasonable while improving the sensitivity of their instruments, astronomers use an amazing technique called interferometry. Instead of building a single huge telescope, you can merge the light from several telescopes to act like a much larger telescope. It's a technique that has already revolutionized Earth-based observing - but just wait until it gets into space...

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This week we find out how hard it is to hit the Moon with a laser, and if scientists lose contact with the Mars rovers when they go behind the Sun. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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You can't make a Solar System without a whole lot of dust. And that's the problem. This dust has blocked astronomers views into some of the most fascinating parts of the cosmos. It shields the galactic core, enshrouds newly forming stars and their planets, and blocks our view to churning supermassive black holes, actively feeding in distant galaxies. But new telescopes and techniques are allowing astronomers to peer through this dust, and see these events like never before.

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You?ve heard us talk about capsules, you?ve heard us talk about space suits, well today we take a look at the only currently in use reusable space craft. It?s a not a bird, its not a plane ? It?s the US Space Shuttle. And to make it interesting ? we?ve sent Scott Miller, Astronomy Cast student web developer, down to watch the launch so he can bring us back us first hand story.

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Orbiting black holes generate gravity waves. This week Bob Novella of Skeptics Guide to the Universe is going to pepper Pamela with questions, testing her ability to leap from tides to gravitational waves to Higgs bosons. We'll see where this takes us on this skeptical journey through what is known and what we're trying to learn about this universe.

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Dreaming up new planets is a favorite pastime of science fiction writers, but the universe often has them beat ? coming with planets in place and forms that we had quite thought to imagine. Today we know of 228 stars orbiting alien stars, and in this episode we will look at the diversity of these worlds, from Mushy Lava covered planets to Icy Giants to the hottest of hot Jupiters.

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This week we find out if moons around other planets could support life, if there's anything out there between galaxies, and whether stars form rings. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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The space capsule has been around for almost 50 years, when Yuri Gagarin headed to space in 1961. There have been many programs that used capsules by both the Americans and the Russians, and even the Chinese are using them now for their spaceflight program. Let's take a look at this rugged, dependable space vehicle that going to making a comeback in the next decade, when NASA sends humans back to the Moon.

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As astronomers discovered that we live in a great big universe, they considered a fundamental question: is the universe the same everywhere? Imagine if gravity was stronger billions of light years away? Or in the past. It sounds like a simple question, but the answer has been tricky to unravel.

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We did a wildly popular three part series about the center, size and shape of the Universe. But every good trilogy needs a 4th episode. This week we look at age of the Universe. How old is the Universe, and how do we know? And how has this number changed over time as astronomers have gotten better tools and techniques?

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This week we find out when stars get torn apart from gravity, how we can see supermassive black holes, how liquid water could have existed on Mars in the past, and much more. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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As we've mentioned before, the Universe is trying to kill you. And for astronauts, that's truer than ever. One step out into the vacuum of space would be a world of hurt for an unprotected astronaut: the freezing cold temperature, the lack of atmospheric pressure, and the deadly radiation, just to name a few hazards. That's why the smart astronaut always puts on a spacesuit first. Let's take a look at the smallest spaceship around.

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With Christmas just around the corner, we thought we'd investigate a mystery that has puzzled historians for hundreds of years. In the bible, the birth of Jesus was announced by a bright star in the sky that led the three wise men to his birthplace. What are some possible astronomical objects that might look like such a bright star in the sky? And were there any unusual events that happened at that time?

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This week we find out the difference between an astronomer, an astrophysicist, and a cosmologist, the search for the stars that shared our nebula, hidden objects in Lagrange points, and much more. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Space is totally inhospitable. If the freezing temperatures don't get you, the intense radiation will kill you. Or the vacuum, or the lack of breathable atmosphere, or meteoroid impacts. Well? you get the idea. That's why most space exploration is done by hardy robots. They don't need to eat, drink or breathe. They get their energy from the Sun, and they've proven they've got the right stuff to explore every planet and major moon in the Solar System. Let's hear it for the space robots.

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This week we find out the distance between Betelgeuse and Bellatrex, how astronomers measure distance between objects, the possibility that an object could mess up the orbit of Earth, and the reason for different sizes of stars.

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In the old days, astronomers had to beg for telescope time. They'd put together a proposal, convince observatories to gather data for them, crunch that data and release the results. No telescope, no results. But everything's different now. Fleets of robotic telescopes constantly scan the skies, building up a vast database of raw data about the Universe. Anyone who wants can access the information through the Internet, download what they need to do real science. No telescope necessary. Let's look at the development of sky surveys, and how they're changing how astronomy gets done.

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Today, time rules our lives. We live each day with the moments broken up into hours, minutes and seconds. We never seem to have enough time. But can you imagine not being able to tell time at all, where the movements of the Sun and the stars was the only way to know what time it was? Let's learn about the history of time, methods of telling time, and Einstein's historic discovery that time isn't as fixed as we thought it was.

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As part of her trip to England, Pamela had a chance to sit down with Oxford astrophysicist Chris Lintott and record an episode of Astronomy Cast. From the first stars to the newest planets, molecules and the chemistry that allows them to form affects all aspects of astronomy. While most astronomers group molecules into three bins of hydrogen, helium and everything else, there are a few who do proper chemistry by studying the sometimes complex molecules that form between the stars.

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It's time for a third lunar chapter. We've talked about the physical characteristics of the Moon, and the exploration. Now we're going to talk about the plans to return to the Moon. From the upcoming lunar reconnaissance orbiter to the plans to have humans set foot on the Moon again, for the first time in more than 50 years.

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This week we explore galactic spiral arms, seismic quakes on the Sun, and our picks for astronomy gear. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Let's continue on our journey to the Moon. Last week we talked about the physical characteristics of the Moon, its appearance in the sky and how it interacts with the Earth. This week we're going to take a look at how scientists have expanded our understanding of the Moon. From ancient astronomers using nothing more than their eyes and the first telescope observations of Galileo to the exploration by robotic spacecraft. And of course, the first tentative steps by the human explorers of the Apollo program.

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Another week, another batch of questions. If ice disappears in your freezer, how can it last in space? How can the Universe be expanding faster than the speed of light? And what is the risk from a coronal mass ejection in an airplane? All this and even more questions. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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Hey, here's a topic we haven't gotten around to yet... the Moon. Today we look at our closest astronomical companion: the Moon. What impact does the moon have on our lives, where did it come from, who walked on it, and are we ever going to walk on it again? We're going to learn about the phases, the tides and even a little bit about NASA's plans to return to the Moon.

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We're back to a themeless questions show. We're right across the Universe this time. Why are the planets lined up in a nice flat plane? Why are there no green stars? And is the Oort Cloud contaminating our understanding of the cosmic microwave background radiation? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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We say it all the time here on Astronomy Cast: the Universe is trying to kill us. This week, Pamela is joined by Dr. Phil Plait to discuss his new book, Death from the Skies. Phil and Pamela talk about asteroid strikes, solar flares and gamma ray bursts.

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Everyone loves a theme. And this week we've collected together some of your questions about relativity. More light speed spacecraft, twin paradoxes, and the mixing up of gravity, time and mass. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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When you think about the best pictures in astronomy, almost every one is a nebula; the pillars of creation in the Eagle Nebula, or the complex Helix Nebula - or my personal favorite, the Ring Nebula. They're beautiful, wispy clouds of gas and dust that signify both the birth and death of stars. Today we give tribute to nebulae.

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Another week, another roundup of your questions. This week listeners asked: what is galactic dust anyway, and where does it come from? Why can photons move at the speed of light? And how can astronomers know what happened right after the Big Bang? And there's even more. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

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You know what this show needs? More aliens. Since we don't seem to have any visiting right now, we're going to have to find some. SETI is an acronym. It stands for the Search for Extraterrestrial Intelligence. But there's more to SETI than just putting up a radio telescope and hoping to catch a glimpse of an alien television broadcast.

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Another week, another roundup of your questions. This week listeners asked: are we all going to die in 2012 when the solar system passes through the galactic plane? Did Venus make the Moon? And what will extraterrestrials see when the Sun is dead and gone? And there's even more. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show.

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Last week we looked at the complete life of the Sun, birth to death. But stars can be smaller, and stars can get much much larger. And with a change in mass, their lives change too. Let's start the clock again, and see what happens to the smallest stars in the Universe; and what happens to the largest.

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Another week, another roundup of your questions. This week listeners asked: if forces are communicated through particles, can we run out? If you were traveling at light speed, when would you know to stop? And there's even more. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show.

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We've talked about the Sun before, but this time we're going to look at the entire life cycle of the Sun, and all the stages it's going to go through: solar nebula, protostar, main sequence, red giant, white dwarf, and more. Want to know what the future holds for the Sun, get ready for the grim details.

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Another week, another roundup of your questions. This week listeners asked: will reaching light speed destroy the Universe? When is Andromeda going to look really, really cool with the unaided eye? Why didn't dark matter all turn into black holes? And there's even more. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show.

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Look around you. Breathe in some air. Everything you can see and feel was formed in a star. Today we'll examine that long journey that matter has gone through, forged and re-forged in the hearts of stars. In fact, the device you're using to listen to this podcast has some elements formed in a supernova explosion.

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As you know, we wanted to answer listener questions regularly, but we found it was taking away from the regular weekly episodes of Astronomy Cast. So we've decided to just split it up and run the question shows separately from the regular Astronomy Cast episodes. If this works out, you might be able to enjoy twice the number of Astronomy Cast episodes. So if you've got a question on a topic we cover in a recent show, or you just have a general astronomy question, send it in to info@astronomycast.com. Either by email, or record your question and email in the audio file.

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At the earliest moments of the Universe, there were no separate forces, energy or matter. It was all just the same stuff. And then the different forces froze out, differentiating into electromagnetism, the strong force and the weak force. Today we'll look at the problem that has puzzled physicists for generations: is there a single equation that explains all the forces we see in the Universe. Is there a theory of everything?

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This is our forth installment in our series of student questions shows and these questions come to us from Leelanau High School.

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After a quick Dragon*Con break, we're back to our tour through the fundamental forces of the Universe. We've covered gravity and electromagnetism, and now we're moving onto the strong and weak nuclear forces. We didn't think they'd really need to be separate episodes, so we're putting them together. And then we'll cap the whole series with the quest for the theory of everything.

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Pamela left Fraser behind (with sorrow) and took on Dragon*Con and the facts (or lack there of) in Science Fiction. Helping her out were special guests Phil Plait and Kevin Grazier.

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Our series on the basic forces of the cosmos continues! Last week we discussed gravity, and this we'll handle electromagnetism. Electricity and magnetism are just two aspects of the same force, and you can't talk about astronomy without understanding these two keys aspects of physics.

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You seem to like a nice series, so here's a new one we've been thinking about. Over the course of the next 4 weeks, we're going to cover each of the basic forces in the Universe. And this week, we're going to start with gravity; the force you're most familiar with. Gravity happens when masses attract one another, and we can calculate its effect with exquisite precision. But you might be surprised to know that scientists have no idea why gravity happens.

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Last week we talked about rockets. How they work and their limitations. This week we're going to look at the future of propulsion systems. From the ion engines that are already working to explore the Solar System to the prototype solar sails to futuristic technologies like magnetic sails, and bussard ramjets. This is how we'll travel to other stars.

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To move around in space, you need some kind of propulsion system. And for now, that means rockets. Let's learn the underlying science of rockets, and how they work. And learn why a rocket will never let us reach the speed of light.

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The Milky Way is our home. An island of stars in a universe of other galaxies. But you might be surprised to learn that astronomers have only known the Milky Way's true nature for just a century. Let's learn the history of discoveries about the Milky Way, and what today's science tells us. And let's peer into the future to learn the ultimate fate of our galaxy.

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Last week we talked about galaxies in general, and hinted at the most violent and energetic ones out there: active galaxies. Quasars have been a mystery for half a century; what kind of object could throw out more radiation than an entire galaxy? A black hole, it turns out, with the mass of hundreds of millions of suns performs this feat. Let's trace back the history of quasars, how they were first discovered and puzzled astronomers for so long. And let's look at what we know today.

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This week we're going to look at some of the biggest objects in the Universe: galaxies. It was the discovery of galaxies in the early 20th century that helped astronomers realize just how big the Universe is, and how far away everything is. Let's learn how galaxies formed and how they evolve and change over time, merging with the neighbors. And what the future holds.

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And now we reach the third part of our trilogy on the human exploration and colonization of Mars. Humans will inevitably tire of living underground, and will want to stretch their legs, and fill their lungs with fresh air. One day, we'll contemplate the possibility of reshaping Mars to suit human life. Is it even possible? What technologies would be used, and what's the best we can hope for?

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After astronauts make the first tentative steps onto the surface of Mars, a big goal will be colonization of the Red Planet. The first trailblazers who try to live on Mars will have their work cut out for them, being in an environment totally hostile to life. What challenges will they face, and how might they overcome them?

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We're learned about the failed missions to Mars in the past, and the current spacecraft, rovers and landers currently exploring the Red Planet. But the real prize will come when the first human sets foot on Mars. Robots are cheaper, but nothing beats having a real human being on the scene, to search for evidence of water and life.

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I know last week was a bit of a dry history lesson, but we wanted to give you some understanding of past efforts to explore Mars. Now we'll look at the missions currently in orbit, and crawling around the surface of Mars, and help you understand the science that's happening right now.

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With last month's safe arrival of the Phoenix Mars Lander, Mars enthusiasts breathed a collective sigh of relief? phew. Now it's time to search for evidence of organic molecules in the ice at Mars' north pole. But this is just the latest in a long series of missions sent to the Red Planet. Let's have a history lesson, and look back at the missions sent to Mars, successful and unsuccessful.

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With the successful touchdown of the Phoenix Lander, NASA is continuing its quest to find evidence of past and present water on Mars. This week we discuss the geologic history of Mars, and explain why NASA thinks the story of water on Mars is so important. And how this ties into the search for life on the Red Planet.

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You've heard us say it 90 times: "How we know what we know." But how do we know how we know what we know? So astronomers like all scientists use the scientific method. Without the scientific method we'd probably still think the Earth is flat, only a few thousand years old and the center of the universe. But with the scientific method everything changes. From biology, to chemistry, to physics, to astronomy it is impossible to count the number of changes that have happened to human society because of changes brought about from the scientific method. In this episode we tell you about what the scientific method is, how you can use it to improve your life, and discuss why gravity isn't just a theory.

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Since the dawn of humanity, astronomers have wished to destroy the atmosphere. Oh sure, it's what we breathe and all, but that stupid atmosphere is always getting in the way. Since destroying the atmosphere is out of the question, astronomers have figured out how to work with it. To distort the mirror of the telescope itself though the magic of adaptive optics.

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Our understanding of the cosmos has been revolutionized by the Hubble Space Telescope. The breathtaking familiar photos, like the Pillars of Creation, pale in comparison to the astounding amount of science data returned to Earth. Hubble's getting old, though, serviced several times already, and due for another mission later this year. Let's relive the historic observatory's amazing life so far, and see what the future holds.

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Hopefully you've all recovered from part 1 of this set, where we make you sad about the future of the humanity, the Earth, the Sun and the Solar System. But hang on, we're really going to bring you down. Today we'll look far far forward into the distant future of the Universe, at timescales that we can barely comprehend.

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This is a show we wanted to do since we started Astronomy Cast but we always thought it was too early. We wanted you to know that we're positive, happy people with enthusiasm for astronomy and the future. It's time for some sadness. It's time for a grim look to see what the future holds for the Universe. This week we stay close to home and consider the end of humanity, the Earth, the Sun, and the entire Solar System. Next week we'll extend out to the very end of the Universe.

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Our senses can only detect a fraction of the phenomena happening in the Universe. That's why scientists and engineers develop detectors, to let us see radiation and particles that we could never detect with our eyes and ears. This week we'll go through them all, so you can understand how we see what we can't see.

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Have you ever wondered what it takes to get a spacecraft off the Earth and into space. And how managers at NASA can actually navigate a spacecraft to another planet? And how does a gravity assist work? And how do they get them into orbit? And how do they land? So many questions?

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Have you ever heard that photons behave like both a particle and a wave and wondered what that meant? It's true. Sometimes light acts like a wave, and other times it behaves like a little particle. It's both. This week we discuss the experiments that demonstrate this, explain how scientists figured it all out in the first place. What does wave/particle duality have to do with astronomy? Well, everything, since light is the only way astronomers can see out into the Universe.

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We're polluting every corner of our own planet, so it only makes sense that we'll take our trashy habits out into space with us. This week we look at the myriad of ways we're messing up space, from the trash orbiting the planet to the radiation we're leaking out into space.

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As predicted we got a lot of questions from people about our trilogy of shows on the size, shape and centre of the universe. Today we'll do our best to clear them all up.As always, if you're still confused drop us an email to info at astronomycast dot com.

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Pamela's attending the 39th Lunar and Planetary Sciences Conference, and you know what that means: the Moon? and planets! When you think of the Moon, you think of craters. In fact, that's a big theme this week at the conference, so Pamela took it as inspiration. Here you go, the week we drove the show into a crater. Wait? there's got to be a better way to describe this.

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We?re ready to complete our trilogy of discovery about the universe. We?ve learned that it has no center; rather everywhere is its center and nowhere. We discovered that the universe seems to be flat. It not open, it is not closed, it is flat. If that doesn?t make any sense, you need to listen to the previous show because there?s no way I could give that an explanation. So now we want to know: ?How big is it?? Does it go on forever or is it finite in scale? How much of it can we see?

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Some of the biggest questions in the universe depend on its shape. Is it curved? Is it flat? Is it open? Those may not make that much sense to you, but in fact it?s very important for astronomers. So which is it? How do we know? How did we figure it out? Why does it matter?

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There are some people ? I?m not naming names ? who think the universe revolves around them. In fact, for most of humankind, everybody thought that. It?s only been in the last few hundred years that scientists finally puzzled out that the Earth isn?t the centre of the universe at all. That begs the question: where is the centre?

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Gravity is always pulling you down, but there are places in the solar system where gravity balances out. These are called Lagrange points and space agencies use them as stable places to put spacecraft. Nature is on to them and has already been using them for billions of years.

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This is our second installment in our series of student questions shows and these questions come to us from Curtis High School.

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After the big bang, all we had was hydrogen, a little bit of helium, and a few other trace elements. Today, we?ve a whole periodic table of elements to enjoy, from oxygen we breathe to the aluminium cans we drink from to the uranium that powers some people?s homes. How did we get from plain old hydrogen to our current diversity? It came from stars, in fact successive generations of stars.

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Sometimes, we don?t get to decide what our show?s about. So many threads come together at the same time driving the decision for us. This is one of those situations. We?ve gotten so many questions from listeners in just the last week about antimatter that our show had just been chosen for it. You command, we obey. Let?s talk about antimatter.

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We?ve been so crazy following our own whims through the universe that we?ve neglected your questions. That ends today. It?s time to dig deep into our overflowing email box to retrieve the puzzling questions our listeners have sent in.

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We?re going to return back to a long series of episodes we like to call: Radiation that Will Turn You Into a Superhero. This time we?re going to look at cosmic rays, which everyone knows made the Fantastic Four. These high-energy particles are streaming from the Sun and even intergalactic space, and do a wonderful job of destroying our DNA, giving us radiation sickness, and maybe (hopefully!) turning us into superheroes.

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When he put together his theories of relativity, Einstein made a series of predictions. Some were confirmed just a few years later, but scientists are still working to confirm others. And one of the most fascinating is the concept of gravitational waves. As massive objects move in space, they send out ripples across the Universe that actually distort the shape of matter. Experiments are in place and in the works to detect these gravitational waves as they sweep past the Earth.

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Just a couple of shows ago, we showed you how to get a career in astronomy. Now that you've got your career in astronomy, obviously the next goal is to win a Nobel prize. We're here at the American Astronomical Society meeting in Austin, which is just one tiny step that a person has to take before you get that Nobel prize. Before you get that call in the middle of the night from Sweden, you're going to need to come with an idea, do some experiments, write a paper, get published and a bunch of other stuff. This week, we'll tell you all about it.

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Thanks to GLAST, Astronomy Cast is now able to provide equipment to send to high school teachers who want to Pamela and Fraser to do a special questions show just for their class. We will be making this shows available on the feed on days other than Monday (that's still reserved for your regularly scheduled Astronomy Cast). This is the first one available and comes with questions from Farmersburg School.

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When it was first developed, the standard model predicted a collection of particles, and thanks to more and more powerful colliders, physicsists have been able to find them all except one: the Higgs-Boson. It's an important one because it should explain how objects have mass. The European Large Hadron Collider should have the power and sensitivity to find the Higgs-Boson.

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This week we're going to study some of the most ancient objects in the entire Universe; globular clusters. These relics of the early Universe contain hundreds of thousands of stars, held together by their mutual gravity. Since they formed together, they give astronomers a unique way to test various theories of stellar evolution.

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With all the enthusiasm that?s being generated with astronomy, it?s had a bit of a strange side-effect. We?ve been causing some of our listeners to have midlife crises about their careers. We?ve had other people who just want advice ? they?re moving into college for the first time and they want to direct the courses they?re going to be taking into astronomy. Some other people already have skills that are very useful and have wondered how they can help up or even change their career to be working in the field. We thought we?d try and answer everyone?s questions all at once and just run through the major career paths you can take that relate to astronomy and space, and the kinds of things you?ll need to do to actually make yourself a good candidate for that field.

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Astronomy is one of the few sciences where amateurs make meaningful contributions to discoveries. Many professional researchers work hand-in-hand with teams of amateurs to make discoveries that just wouldn't be possible without this kind of collaboration. In fact, Pamela regularly relies on dedicated enthusiasts for her data on variable stars.

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All good things come to an end - we now find ourselves in the outer reaches of the solar system where our Sun is hard to distinguish from the other bright stars in the sky. But we're not done with the solar system, there's some stuff that's leftover. This week, we look at the outer reaches of the solar system and how it interacts with the rest of the universe.

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It's been a long journey, 64 episodes, but now we're back where we began: Pluto. Last time we talked about how Pluto lost its planethood status, so we won't go over all that again. This time we're going to talk about Pluto, its moons, the Kuiper belt, and the other icy objects that inhabit the outer Solar System.

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We?ve reached Neptune, the final planet in our tour through the solar system ? but don?t worry! The tour?s not over, but after this week we?ll be all out of planets. Neptune has a controversial story about its discovery, some of the strongest winds in the solar system and some weird moons.

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This week, we're on to the next planet in the solar system. We don't know a whole lot about this blue gas planet, but today we'll cover some of the neat stuff we do know, including it's faint rings, sideways axis of rotation and its rocky core - a first in the gas planets we've encountered so far in our tour.

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We know that delaying this show one more week would be too dangerous, so here you go: Saturn's moons. These are some of the most interesting objects in the Solar System, from the spongy Hyperion, to the geysers on Enceladus, to the rainy, misty, oceany Titan. They've kept Cassini busy for years, and scientists will likely be pondering them for decades.

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It's about time for a question show again, so we'll have one last interruption to our planetary tour, to deal with the questions that arose from our inflation show.So if you still don?t understand inflation, take a listen to this week's show and as always, send us your questions.

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Returning to our journey through the solar system, let's voyage away from the largest planet to the second largest, Saturn. Once again, we'll break up our visit because there's lots to talk about. This week, we talk about Saturn and its famous rings. Next week, we'll discuss its many moons.

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We interrupt this tour through the solar system to bring you a special show to deal with one of our most complicated subjects: the big bang. Specifically, how it's possible that the universe could have expanded faster than the speed of light. The theory is called the inflationary theory, and the evidence is mounting to support it. Einstein said that nothing can move faster than the speed of light, and yet astronomers think the universe expanded from a microscopic spec to become larger than the solar system, in a fraction of a second.

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Last week we talked about Jupiter and we could sense right away it would be too much to handle. This week, we'll talk about Jupiter's moons - how many are there? What makes them so interesting? Is it true that the most likely place in the solar system to find life (other than Earth) is actually on one of Jupiter's moons? Hang on tight. We're going to cover a lot.

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Last week we talked about rubble, this week we're going to dig into the largest planet in the Solar System: Jupiter, but will it all just be hot gas? There's so much to talk about, we've decided to break this up into two shows. This week we're going to just talk about Jupiter, and then next week, we're going to cover its moons.

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In the last few weeks we've had many emails saying that our tour of the solar system would not be complete without a show on the asteroid belt. Your wish is our command! We talked about Mars in episode 52, and now that we're back on track our next stop is the asteroid belt.

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It's been a while, so let's catch up with the listener questions. We've got some easy ones, some hard ones and probably some impossible ones. We talk about our universe as a black hole, tidal locking of planets like Uranus, colours of stars at different ages, our universe's birthday and more.

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This is a very different episode of Astronomy Cast. As we mentioned last week, Pamela recently attended the Dragon*Con science fiction convention in Atlanta, Georgia. While she was there, she participated in a special live edition of Astronomy Cast with special guest Dr. Kevin Frazier. Kevin is a NASA scientist, and the science consultant for the TV shows Battlestar Galactica and Eureka. He and Pamela work through physics and astronomy in popular science fiction. What they get right, and what they get wrong... so very wrong.

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As a reward to the all the dedicated fans who completed our demographic survey, we released this special episode of Astronomy Cast. As promised, we're now releasing this episode to all of our subscribers. Panspermia is a controversial theory that life on Earth originated? out there. Maybe it started out in a cosmic dust cloud or originated from another planet, but somehow the very first lifeforms made the trip through the vacuum of space and colonized our home planet.

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Today we consider Mars, the next planet in our journey through the Solar System. Apart from the Earth, it's the most explored planet in our Solar System. Even now there are rovers crawling the surface, orbiters overhead, and a lander on its way. It's a cold, dry desert, so why does this planet hold such fascination?

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So, another week, another planet. Last week we discussed Venus, and that means this week it is time for our home planet - Earth.

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Last week we talked about Mercury, so this week our planetary parade proceeds to Venus. It's the brightest object in the sky, the hottest object in the solar system, and it's probably one of the most deadly places to go and visit.

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We're still digging through the thousands of comments and suggestions from the listener survey but we hear your requests and suggestions, and now you get to start reaping the benefits. Today we start our survey of the solar system with Mercury. What mysteries is it hiding from us? How similar is Mercury to the other rocky planets? How much do we really know about this first rock from the Sun?

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Last week we talked about tidal forces within our solar system. This week we're going to expand our view and encompass the entire universe. Some of the most dramatic events originate from tidal forces caused by gravity: other worlds, galaxies, black holes and even entire clusters of galaxies are under this influence.

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Consider the following: we've got tides here on Earth, the Moon only shows one face to the Earth, we've got volcanoes on Io, and ice geysers on Enceladus. All these phenomena originate from a common cause: the force of gravity stretching across space to tug at another world.

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We've discussed star formation in the past, but now we wanted to talk about the different kinds of stellar nurseries we see across the Universe. We know where our Sun came from because we can look out and see different stellar neighborhoods at every stage of development. It takes a village of gas and dust to raise a star.

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This week we wanted to give you a basic physics lesson. This isn't easy physics, this is a lesson on the basic numbers of the Universe. Each of these numbers define a key aspect of our Universe. If they had different values, the Universe would be a changed place, and life here on Earth would never have arisen.

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If you remember way back to Episode 9, we covered Einstein's Theory of Special Relativity. Well, that's only half of the relativity picture. The great scientist made an even more profound impact on physics with his theory of general relativity, replacing Newton with a better model for gravity.

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It's time to answer the questions again. And this time we've got some doozies. Is the Universe rotating? Is space something, or is it nothing? Is dark energy evenly distributed? What would happen if an astronaut went out the airlock, without a spacesuit. Want to know the answers? Well, you've got to listen.

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You probably don't realise it, but magnetic fields are everywhere. We're not talking about the magnets in your speakers, your electronic equipment or on the fridge door. We're talking about the gigantic magnetic fields that surround planets, stars, galaxies and some of the most exotic objects in the Universe.

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The last decade has been the golden age of astronomy, with new observatories and space telescopes pushing out our understanding of the Universe. We can see billions of light years away, watch dynamic events unfold in almost real-time, and see into every corner of the electromagnetic spectrum. Just you wait: things will only get better. Here come the supertelescopes!

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Once again, Pamela does her duty as an astronomer and joins her colleagues at the American Astronomical Society's meeting, held in May, 2007 on Honolulu, Hawaii. With all that sand, surf and sun, how did anyone get any science done? Pamela tracked down the interesting stories, and brought them back so we could analyze them.

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While Pamela's away at the American Astronomical Society meeting, we brought in a special guest to help debunk some of the pseudoscience that people mistake for astronomy. Dr Steven Novella from the Skeptic's Guide to the Universe gets to the bottom of astrology and UFOs, and why they're not real science.

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Huge stars become black holes, and small stars become white dwarfs. But medium-sized stars can become neutron stars; exotic objects that overcome the nuclear force holding protons and electrons apart. What was once the size of a star is compressed down to only a few dozen kilometres across.

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Astronomers are always trying to get their hands on bigger and more powerful telescopes. But the most powerful telescopes in the Universe are completely natural, and the size of a galaxy cluster. When you use the gravity of a galaxy as a lens, you can peer right back to the edges of the observable Universe.

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Gamma ray bursts are the most powerful explosions in the Universe, releasing more energy in a few seconds than our Sun will put out in its lifetime. It's only been in the last few years that astronomers are finally starting to unravel the cataclysmic events that cause these energetic explosions.

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We know there's matter, and we know there's anti-matter. If there's dark matter, is there an anti-dark matter? How come gravity can escape from a black hole? Do black holes capture dark matter? Can a moon have a moon? Can a planet have two stars? If you've had any of these questions, you'll want to listen to this week's show.

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What a week! Astronomers announced the discovery of an Earth-sized planet orbiting the nearby star Gliese 581. We talk about the technique used to discover the planet, the possibilities of finding even smaller planets, and what the future holds for finding another Earth.

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Buying your first telescope can be a nerve-wracking experience filled with buyer's remorse. This week we discuss the basics of purchasing your first binoculars and telescope. What to look for, how to clean older equipment, and how to use it for the first time. Let's make sure your first investment in this wonderful hobby is money well-spent.

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Trillions of neutrinos are produced in our Sun through its nuclear reactions. These particles stream out at nearly the speed of light, and pass right through any matter they encounter. In fact, there are billions of them passing through your body right now. Learn how this elusive particle was first theorized and finally discovered.

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We get questions every week about string theory and topics popularized by science fiction. Here's the problem. There's just no evidence. Each of these is based on wonderful and well-formed mathematical equations, or wishful thinking, but they're very hard (if not impossible) to test in the real Universe.

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It's Spring in the Northern Hemisphere, and that means the Sun is back. But it's more than just a free heat lamp for your garden, it's an incredible, dynamic nuclear reaction complete with flares, coronal mass ejections, twisting magnetic fields and the solar wind. Put in your headphones, head outside and enjoy the sunshine while you listen to this week's podcast.

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This week we're talking about asteroids. And not just any asteroids, but Near Earth Objects. How do astronomers find these things, why are they buzzing around the Earth, what are the chances we'll actually get hit, and what would happen if we did get hit? How could we stop them?

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Come on, admit it, you've had this question. If the Universe is expanding from the Big Bang, what is it expanding into? What's outside the Universe? Ask any astronomer and you'll get an unsatisfying answer. We give you the same unsatisfying answer, but really explain it, so your unsatisfaction doesn't haunt you any more.

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The questions are piling up, so it's time to get through them. We've got a great collection this week. How can our eyes collect so many photons? What's the speed of gravity? Shouldn't the light from the cosmic microwave background radiation passed us by?

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This week we continue the story of galaxy formation, learning how groups of galaxies come together to form the biggest structures around - galaxy superclusters. And when you look at the Universe at this scale, environment is everything.

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Our Milky Way is a complex and majestic barred spiral galaxy. But 13.7 billion years ago it began, like all galaxies, from the elementary particles formed in the Big Bang. How did our galaxy grow from nothing to the hundreds of billions of stars we see today?

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We live in a mind bogglingly big Universe filled with countless stars. We know intelligent life evolved here on Earth. It must be common across the Universe, right? But if there's life out there, how come we haven't been visited by aliens yet? Why haven't we even picked up signals from alien television stations? Where's all the life?

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If you're wondering how many extraterrestrials there are in our galaxy, you just have to use a simple equation developed by astronomer Frank Drake in 1961. Just find out how many stars there are, how many support life, how many advanced societies form, and a few other details and we'll be set.

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Our Sun has been around for billions of years, and will last for billions more. We're lucky, it's pretty stable and regular as stars go, only changing in brightness a little now and then. But there are stars out there that change dramatically; astronomers call them variable stars, and they demonstrate just how bizarre and dangerous the Universe can be.

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Our episode on black holes generated many many questions from listeners. We dip into this bottomless pool of questions and start dealing with them. Are really big black holes like the Big Bang? How can black holes evaporate? What would it look like to stand on a black hole? And just how large would a rock have to be before its gravity is so strong that a human can't escape?

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It's astronomical society get together time, and we send Pamela to investigate and record. Hear the latest news that will make your text books out of date. Find out where all the dark matter is collecting, the identity of Kepler's supernova, and new insights into the closest, brightest supernova in recent memory.

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The sudden brightening of Comet McNaught has reminded us what a treat it can be to see a comet with the unaided eye. A diffuse ball with a long tail stretching across the sky. There's nothing else in the night sky that can compare to a bright comet. But what are these objects, where do they come from, and what can they tell us about the formation of the Solar System?

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We're finally ready to deal with the topic you've all been waiting for: Schwarzschild swirlers, Chandrasekhar crushers, ol' matter manglers, sucking singularities - you might know them as black holes. Join as as we examine how black holes form, what they consume, and just how massive they can get.

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We take the Moon for granted, but its effect on the Earth is very important; possibly even critical for the formation of life. But where did it come from? Did the Earth and Moon form together? Or did the Earth capture a wayward Moon? Or was there a more catastrophic cause to this lunar mystery?

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We see the Universe in visible light with our photon detecting eyes. We can feel infrared heat with our photon detecting hands, and we get sunburns with our ultraviolet photon detecting skin (ouch). But there's a whole spectrum of photons out there, from radio waves to gamma rays that astronomers use to understand the Universe. It's time to see the whole picture.

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We finally get organized enough deal with several listener questions: isn't dark matter just regular stuff we can't see? how can parts of the Universe be expanding faster than the speed of light? what will Betelgeuse look like when it explodes as a supernova? what's the speed of gravity? All these and more questions are answered.

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No more suspense. This week we blow the biggest stars up. Kaboom. Want more details? Then you've got to listen.

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We've celebrated the birth of new stars, but the stellar lifecycle doesn't end there. Stars like our Sun will spend billions of years fusing together hydrogen and pumping out energy. And when the fuel runs out, their death is as interesting as their birth. This week Fraser and Pamela trace out this stellar evolution, and explain what the future holds for stars, large and small.

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Most parents have had that uncomfortable conversation with their children at some point. Mommy, Daddy, where do stars come from? You hem and haw, mumble a few words about angular momentum and primordial hydrogen and then cleverly change the subject. Well, you don't have to avoid the subject any longer. Pamela and Fraser describe formation of stars, large and small, in a tasteful manner, using only understandable and scientific language.

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The discovery of dark energy was one of the biggest surprises in astronomy. Instead of a nice, predictable expanding Universe, acted on only by gravity, astronomers turned up a mysterious repulsive force accelerating the expansion of the Universe. Fraser and Pamela explain the evidence for a dark energy, and a few possible theories for what could be providing this repulsive force

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You hear distances all the time in astronomy. This star is 10 light-years away; that galaxy is 50 million light-years away; that Big Bang over there happened 13.7 billion years ago. But how did astronomers actually figure out how far away everything is? It's not a single measuring stick. Instead, astronomers have built up a series of overlapping measuring tools (yes, we're calling supernovae and variable stars tools), which take us from right around the corner to very ends of the Universe. Get out your ruler... no, the bigger one... never mind... just listen.

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It's all relative. How many times have you heard that? Well, when you're traveling close to the speed of light, everything really is relative; especially the passage of time. This week, Fraser and Pamela give you the skinny on Einstein's Special Theory of Relativity. After listening to a few thought experiments, you too should be able to wrap your head around this amazing theory.

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Dress warmly, gather some friends and family, and head outside to watch sand burn in the upper atmosphere. There's nothing like a good meteor shower. Fraser and Pamela explain this beautiful phenomenon: what causes them, the best storms and showers to watch for, and different types of meteors you might see.

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Got your eye on that $40 telescope at Walmart? Wait, hear us out first! Fraser and Pamela discuss strategies for getting into amateur astronomy - one of the most worthwhile hobbies out there. We discuss what gear to get, where to look, and how to meet up with other astronomy enthusiasts.

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Last week's episode started out with a bang- a Big Bang. This week we continue our discussion into the beginning of everything. We present three additional lines of evidence that have led astronomers to the conclusion that our Universe started out as a singularity 13.7 billion years ago, and has been expanding ever since.

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As a tribute to John Mather and George Smoot, the two leaders of the Cosmic Microwave Background Explorer (COBE) satellite science team, and winners of this year's Nobel Prize for Physics, we head back to the beginning of everything- the Big Bang. Follow as we trace the Big Bang's discovery, and one of the most important lines of evidence: the cosmic microwave background radiation which was predicted by theory and then discovered by accident.

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Dark matter . . . What is it? Nobody knows for sure, but it's definitely there. Or maybe it's not there, and we just need some redefinition of gravity at vast scales. Join Fraser and Pamela as we discuss the discovery, detection, and possible explanations of dark matter.

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You have lived on the Earth all your life, so you'd think you know plenty about planets. As usual though, the Universe is stranger than we assume, and the planets orbiting other stars defy our expectations. Gigantic super-Jupiters whirling around their parent stars every couple of days; fluffy planets with the density of cork; and Earth-sized fragments of exploded stars circling pulsars. Join us as we round up the latest batch of bizarro worlds.

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Look down at your feet. There... you're looking at a planet. Now look into the night sky and you should be able to spot a few more. After that, spotting additional planets becomes really hard, especially when you're trying to find them orbiting other stars. This week we discuss the techniques astronomers use to locate distant worlds.

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Pluto. It's a planet, then it's not. This week we review Pluto's history, from discovery to demotion by the International Astronomical Union. Learn the 3 characteristics that make up a planet, and why Pluto now fails to make the grade.

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