Universe Today Video

Black holes want to absorb all matter and energy in the Universe. It's just a matter of time. So what can we do to fight back? What superweapons have been devised to destroy black holes? Black holes are the natural enemies of all spacefaring races. With their bottomless capacity to consume all light and matter, it’s just a few septillion years before all things in the Universe have found their way into the cavernous maw of a black hole, crushed into the infinitely dense singularity. If Star Trek has taught us anything, it’s that it’s mankind’s imperative to survive against all odds. So will we take this lying down? Heck no! Will we strike first and destroy the black holes before they destroy us? Heck yes! But how? How could you kill a black hole? This... gets a little tricky. For a black hole, any matter entering the event horizon is added to the mass. Shoot bullets at a black hole, and you just make a slightly more massive, slightly more dangerous black hole. Detonate a nuclear bomb inside the event horizon, and you only make the black hole more massive. Fire your forward phasers at the black hole, and that’ll still make it even more massive. Swap those bullets in for lasers and black holes don’t care. Within the event horizon, energy and matter are one, and those very same black holes can convert that energy into mass. So all your projectiles and energy weapons inevitably just make it more dangerous. What if we crashed a star into it? Would that fill it up, or burn it out? Nope. It would just gobble that star up, and go on with its business. If we smashed another black hole into it? Would that tear it apart? The cause is also the cure? Not even maybe. As soon as black holes get within each other’s event horizons, they’ll just merge into a more massive, and even nastier, meaner black hole. Number 1, it’s time to bring out the big guns. Reverse the particle flow, flood the dilithium chamber with exotic particles and route it through the main deflector dish, and construct your own black hole out of antimatter. Then kamikaze this new antimatter black hole right into a the black hole you want to destroy. Would that do it? Would that solve our problem? As you probably know, when you crash matter into antimatter, you get an explosion of pure energy. It’s the most perfect energy weapon we can envision. Unsurprisingly, this brings its own set of complications. It’s not entirely clear you’ve still have antimatter in your antimatter black hole. It’s possibly been converted into a regular flavour black hole. Still, if you *could* crash an antimatter and regular matter black hole together, you would get an incomprehensible explosion. Converting that entire dense and gigantic mass into pure energy, as calculated by Einstein. As soon as you did, all that energy would be immediately converted... into more black hole. Nothing, not even light itself can escape a black hole. That includes all your magnificent explosion energy from your antimatter impact. You wouldn't even see it happen. You’d just end up with a black hole with twice the mass. And that might be just what it wants. As we learned in a previous episode, we can extract angular momentum from a black hole. By dropping material into the event horizon, we can remove energy and slow its rotation. We can even bring it to a stop. So we can slow down its spin, but that won’t make it go away. So, is that it, are we out of options? Good news, we have one last strategy, and it’s so crazy it just might work. According to Stephen Hawking, black holes can actually evaporate over enormous periods of time. Virtual pairs of particles are constantly popping into existence all around us. Then they recombine in a flash and disappear from the Universe. When one of these particle pairs appears right on the edge of a black hole, one particle falls into the black hole, and the other is free to fly off into space. And here’s the amazing thing.

The Earth has a single moon, while Saturn has more than 60, with new moons being discovered all the time. But here’s a question, can a moon have a moon? Can that moon’s moon have its own moon? Can it be moons all the way down? First, consider that we have a completely subjective idea of what a moon is. The Moon orbits the Earth, and the Earth orbits the Sun, and the Sun orbits the center of the Milky Way, which orbits within the Local Group, which is a part of the Virgo Supercluster. The motions of objects in the cosmos act like a set of Russian nesting dolls, with things orbiting things, which orbit other things. So maybe a better question is: could any of the moons in the Solar System have moons of their own? Well actually, one does. Right now, NASA’s Lunar Reconnaissance Orbiter is happily orbiting around the Moon, photographing the place in high resolution. But humans sent it to the Moon, and just like all the artificial satellites sent there in the past, it’s doomed. No satellite we've sent to the Moon has ever orbited for longer than a few years before crashing down into the lunar surface. In theory, you could probably get a satellite to last a few hundred years around the Moon. But why? How come we can’t make moons for our moon to have a moon of it’s own for all time? It all comes down to gravity and tidal forces. Every object in the Universe is surrounded by an invisible sphere of gravity. Anything within this volume, which astronomers call the “Hill Sphere”, will tend to orbit the object. So, if you had the Moon out in the middle of space, without any interactions, it could easily have multiple moons orbiting around it. But you get problems when you have these overlapping spheres of influence. The strength of gravity from the Earth tangles with the force of gravity from the Moon. Although a spacecraft can orbit the Moon for a while, it’s just not stable. The tidal forces will cause the spacecraft’s orbit to decay until it crashes. But further out in the Solar System, there are tiny asteroids with even tinier moons. This is possible because they’re so far away from the Sun. Bring these asteroids closer to the Sun, and someone’s losing a moon. The object with the largest Hill Sphere in the Solar System is Neptune. Because it’s so far away from the Sun, and it’s so massive, it can truly influence its environment. You could imagine a massive moon distantly orbiting Neptune, and around that moon, there could be a moon of its own. But this doesn't appear to be the case. NASA is considering a mission to capture an asteroid and put it into orbit around the Moon. This would be safer than having it orbit the Earth, but still keep it close enough to extract resources. But without any kind of orbital boost, those tidal forces will eventually crash it onto the Moon. So no, in our Solar System, we don’t know of any moons with moons of their own. In fact, we don’t even have a name for them. What would you suggest?

NASA’s Galileo spacecraft arrived at Jupiter on December 7, 1995, and proceeded to study the giant planet for almost 8 years. It sent back a tremendous amount of scientific information that revolutionized our understanding of the Jovian system. By the end of its mission, Galileo was worn down. Instruments were failing and scientists were worried they wouldn't be able to communicate with the spacecraft in the future. If they lost contact, Galileo would continue to orbit the Jupiter and potentially crash into one of its icy moons. Galileo would certainly have Earth bacteria on board, which might contaminate the pristine environments of the Jovian moons, and so NASA decided it would be best to crash Galileo into Jupiter, removing the risk entirely. Although everyone in the scientific community were certain this was the safe and wise thing to do, there were a small group of people concerned that crashing Galileo into Jupiter, with its Plutonium thermal reactor, might cause a cascade reaction that would ignite Jupiter into a second star in the Solar System. Hydrogen bombs are ignited by detonating plutonium, and Jupiter’s got a lot of hydrogen.Since we don’t have a second star, you’ll be glad to know this didn't happen. Could it have happened? Could it ever happen? The answer, of course, is a series of nos. No, it couldn't have happened. There’s no way it could ever happen… or is there? Jupiter is mostly made of hydrogen, in order to turn it into a giant fireball you’d need oxygen to burn it. Water tells us what the recipe is. There are two atoms of hydrogen to one atom of oxygen. If you can get the two elements together in those quantities, you get water. In other words, if you could surround Jupiter with half again more Jupiter’s worth of oxygen, you’d get a Jupiter plus a half sized fireball. It would turn into water and release energy. But that much oxygen isn't handy, and even though it’s a giant ball of fire, that’s still not a star anyway. In fact, stars aren't “burning” at all, at least, not in the combustion sense. Our Sun produces its energy through fusion. The vast gravity compresses hydrogen down to the point that high pressure and temperatures cram hydrogen atoms into helium. This is a fusion reaction. It generates excess energy, and so the Sun is bright. And the only way you can get a reaction like this is when you bring together a massive amount of hydrogen. In fact… you’d need a star’s worth of hydrogen. Jupiter is a thousand times less massive than the Sun. One thousand times less massive. In other words, if you crashed 1000 Jupiters together, then we’d have a second actual Sun in our Solar System. But the Sun isn't the smallest possible star you can have. In fact, if you have about 7.5% the mass of the Sun’s worth of hydrogen collected together, you’ll get a red dwarf star. So the smallest red dwarf star is still about 80 times the mass of Jupiter. You know the drill, find 79 more Jupiters, crash them into Jupiter, and we’d have a second star in the Solar System. There’s another object that’s less massive than a red dwarf, but it’s still sort of star like: a brown dwarf. This is an object which isn't massive enough to ignite in true fusion, but it’s still massive enough that deuterium, a variant of hydrogen, will fuse. You can get a brown dwarf with only 13 times the mass of Jupiter. Now that’s not so hard, right? Find 13 more Jupiters, crash them into the planet? As was demonstrated with Galileo, igniting Jupiter or its hydrogen is not a simple matter. We won’t get a second star unless there’s a series of catastrophic collisions in the Solar System. And if that happens… we’ll have other problems on our hands.

Forget Mars, the place we really want to go looking for life is Jupiter's moon Europa. Dr. Mike Brown, a professor of planetary science at Caltech, explains what he finds so fascinating about this icy moon, and the potential we might find life swimming in its vast oceans. "I'm Mike Brown, and I'm a professor of planetary astronomy at Caltech. I study anything you can do in the solar system with telescopes, mostly the outer solar system." Why Europa? "I find Europa one of the most fun bodies in the solar system, mostly because if you were just looking around the solar system looking for an object that was interesting in some way, interesting in the sense that it has a lot of liquid water. You would look at the Earth and say, yep, a lot of water there, that's pretty cool. The next place you would look is Europa - it has the most amount of liquid water of anywhere in the solar system. So it has to be an interesting place, simply by virtue of having that much liquid water. And one of the things I'm most interested in is trying to understand what else is in that ocean besides the water. What is the chemical composition of the salts in that ocean? An understanding the composition leads you to understand things like if the conditions are the types of conditions that might be conducive to life. I'm not going to say that they tell you if there is life or not, but they are the sorts of things that can tell you that it's chemically rich that life might enjoy or if it's kind of a sterile environment. And we've been learning about the composition of the ocean by looking at the surface of Europa where, in cracks or geysers or some way the ocean gets onto the surface and evaporates, and the salts get out on the surface, and we study those salts to tell what's there." How do we get under the ice? Exploring underneath the ice of Europa is hard, but one of the nice early steps would be that you can just land on the surface and the surface has stuff from the ocean, so you can just scrape it off the surface and take a taste of it and see what the ocean is like. But if you really want to get down below and swim around in the ocean and explore, and who wouldn't? In the proposed missions that I've heard, and in the only one that seems semi-viable, you land on the surface with basically a big nuclear pile, and you melt your way down through the ice and eventually you get down into the water. Then you set your robotic submarine free and it goes around and swims with the big Europa whales." Is there a specific chemical they should be looking for? It's hard to imagine that you could find anything even a chemical signature inside the ocean that would really push the idea that there must life under there making it happen, and the reason that it would be hard to find something that would make it so obvious is that we know so little about the core composition of Europa and it's interaction sea water. And many different things could be going on to cause all sorts of disequilibrium chemistry, and that's sort of what you're always looking for - chemical species that shouldn't be there if everything was just in regular equilibrium. And there's so many reasons that you might have it on Europa - you have interactions with the core, a strong radiation environment - that it would be very difficult, I think, to come up with a really sound chemical fingerprint that life must exist there."

You've probably heard the saying “everything’s relative”. When you consider our place in the Universe, everything really is relative. I’m recording this halfway up Vancouver Island, in the Pacific Ocean, off the West Coast of Canada. And where I’m standing is about 6,370 kilometers away from the center of the Earth, that way. From my perspective, the Sun is over there. It’s as large as a dime held at arm’s length. For me it’s really, really far away. In fact, at this exact time it’s further away than any object I you can see with the naked eye.I’m about 150 million kilometers away from the Sun, and so are you. We’re carving out an elliptical orbit which takes one full year to complete one whole trip around. You, me and the Earth are all located inside our Solar System. Which contains the Sun, 8 planets and a vast collection of ice, rocks and dust. We’re embedded deep within our galaxy, the Milky Way. It’s a big flat disk of stars measuring up to 120,000 light years across. Our Solar System is located in the middle of this galactic disk. And by the middle, I mean the center of the galaxy is about 27,000 light years that way, and the edge of the galaxy is about the same distance that way. Our Milky Way is but one galaxy in a larger collection of galaxies known as the Local Group. There are 36 known objects in the local group. Which are mostly dwarf galaxies. However, there’s also the Triangulum Galaxy, the Milky Way, and the Andromeda galaxy... which is by far the largest, most massive object in the Local Group, It’s twice the size and 4 times the mass of the Milky Way. But where is it? From me, and you, Andromeda is located just an astronomically distant 2.5 million light years that way. Or would that be just short 2.5 million light-years that away? I’m sure you see where this is going. The Local Group is embedded within a much larger group known as the Virgo Supercluster, containing at least 100 galaxy groups and clusters. The rough center of the supercluster is in the constellation Virgo. Which as of right now, is that way, about 65 million light years away. Which certainly makes the 2.5 million light years to Andromeda seem like an afternoon jaunt in the family car. Unsurprisingly, The Virgo Supercluster is a part of a larger structure as well. The Pisces-Cetus Supercluster Complex. This is a vast filament of galactic superclusters measuring about 150 million light years across AND a billion light years long. The middle is just over that way. Right over there. One billion light years in length? Well that makes Andromeda seem right around the corner. So where are we? Where are you, and I and the Earth located in the entire Universe? The edge of the observable Universe is about 13.8 billion light years that way. But it’s also 13.8 billion light years that way. And that way, and that way. And cosmologists think that if you travel in any direction long enough, you’ll return to your starting point, just like how you can travel in any one direction on the surface of the Earth and return right back at your starting point. In other words, the Earth is located at the very, very center of the Universe. Which sounds truly amazing. What a strange coincidence for you and I to be located right here. Dead center. Smack dab right in the middle of the Universe. Certainly makes us sound important doesn't it? But considering that every other spot in the Universe is also located at the center of the universe. You heard me right. Every single spot that you can imagine inside the Universe is also the center of the Universe. That definitely complicates things in our plans for Universal relevance. And all this sure does make Andromeda seem close by....and it’s still just right over there, at the center of the Universe. Oh, and about every spot in the universe being the center of the Universe? Well, we’ll save that one for another episode.

There is nothing in the Universe more awe inspiring or mysterious than a black hole. Because of their massive gravity and ability to absorb even light, they defy our attempts to understand them. All their secrets hide behind the veil of the event horizon. What do they look like? We don’t know. They absorb all the radiation they emit. How big are they? Do they have a size, or could they be infinitely dense? We just don’t know. But there are a few things we can know. Like how massive they are, and how fast they’re spinning. Wait, what? Spinning? Consider the massive star that came before the black hole. It was formed from a solar nebula, gaining its rotation by averaging out the momentum of all the individual particles in the cloud. As mutual gravity pulled the star together, through the conservation of angular momentum it rotated more rapidly. When a star becomes a black hole, it still has all that mass, but now compressed down into an infinitesimally smaller space. And to conserve that angular momentum, the black hole’s rate of rotation speeds up… a lot.The entire history of everything the black hole ever consumed, averaged down to a single number: the spin rate. If the black hole could shrink down to an infinitely small size, you would think that the spin rate might increase to infinity too. But black holes have a speed limit. "There is a speed limit to the spin of a black hole. It's sort of set by the faster a black hole spins, the smaller is its event horizon." That’s Dr. Mark Morris, a professor of astronomy at UCLA. He has devoted much of his time to researching the mysteries of black holes. "There is this region, called the ergosphere between the event horizon and another boundary, outside. The ergosphere is a very interesting region outside the event horizon in which a variety of interesting effects can occur." Imagine the event horizon of a black hole as a sphere in space, and then surrounding this black hole is the ergosphere. The faster the black hole spins, the more this ergosphere flattens out. "The speed limit is set by the event horizon, eventually, at a high enough spin, reaches the singularity. You can't have what's called a naked singularity. You can't have a singularity exposed to the rest of the Universe. That would mean that the singularity itself could emit energy or light and somebody outside could actually see it. And that can't happen. That's the physical limitation of how fast it can spin. Physicists use units for angular momentum that are cast in terms of mass, which is a curious thing, and the speed limit can be described as the angular momentum equals the mass of the black hole, and that sets the speed limit." Just imagine. The black hole spins up to the point that it’s just about to reveal itself. But that’s impossible. The laws of physics won’t let it spin any faster. And here’s the amazing part. Astronomers have actually detected supermassive black holes spinning at the limits predicted by these theories. One black hole, at the heart of galaxy NGC 1365 is turning at 84% the speed of light. It has reached the cosmic speed limit, and can’t spin any faster without revealing its singularity. The Universe is a crazy place.

When astronomers first discovered other planets, they were completely unlike anything we've ever found in the Solar System. These first planets were known as "hot jupiters", because they're giant planets - even more massive than Jupiter - but they orbit closer to their star than Mercury. Dr. Heather Knutson, a professor at Caltech explains these amazing objects. "My name is Heather Knutson, and I'm a professor in the planetary science department here at Caltech. I study the properties of extrasolar planets, which are planets that orbit stars other than the sun, so mostly these are our closest exoplanetary neighbors. We're not talking about planets in other galaxies - we're mostly talking about planets which are in the same part of our own corner of our galaxy. So these are around some of the closest stars to the sun." What is a hot jupiter? "The planets that I've found the most surprising, out of all of the ones I've discovered so far, I guess the sort of classic example, is that we've see these sorts of giant planets which are very similar to Jupiter, but orbit very much closer in than Mercury is to our sun, so these planets orbit their sun every two or three days and are absolutely getting roasted. We know that they couldn't have formed there - they had to have formed farther out and migrated in, so what we're still trying to understand are what are the forces that caused them to migrate in, whereas Jupiter seems to have migrated a little bit but more or less stayed put in our own solar system." What do hot jupiters mean for our understanding our own Solar System? "The implications of these "hot jupiters" as we call them are actually huge for our own solar system, because if you want to know how many potentially habitable earthlike planets are out there, having one of these giant planets just rampage their way though the inner part of the planetary system, and it could toss out your habitable earth and put it into either a much closer orbit or a much further orbit. So knowing how things have moved around will tell you a lot about where you might find interesting planets." What is their atmosphere like? "So, the atmospheres of hot jupiters are very exotic, by solar system standards. They typically have temperatures of a thousand to several thousand Kelvin, so at these temperatures these planets could have clouds of molten rock, for example. They have atmospheric compositions that would seem very exotic to us - they're actually more similar to the compositions of relatively cool stars, so we have to adapt to describe these planets - we actually use stellar models to describe their atmospheres. We think that they're also probably also tidally locked, which is very interesting because it means that one side of the planet is getting all of the heat and the other side is sort of in permanent night. And one thing we do is to try and understand the effect that has on the weather patterns on these planets, so you have winds that are pretty good at carrying that around the night side and mixing everything up, or do these planets have these just extreme temperature gradients between the day side and the night side." How'd they get there? "So, we have a couple of theories for how hot jupiters may have ended up in their present day orbits. One theory is, that after they formed, that they were still embedded in the gas disc where they formed, and maybe they interacted with the disc as such that it kind of torqued and pulled them and so that's kind of an early migration theory. There's also a late migration theory version where when after the disc had gone away, these planets had interacted with a third body in the system, so maybe you had another distant massive planet or maybe you had a planet that was part of a binary star system, and those three body interactions excited a large orbital eccentricity in the innermost planet, and once it starts coming in closer to the star,

The Universe is vast bubble of space and time, expanding in volume. Run the clock backward and you get to a point where everything was compacted into a microscopic singularity of incomprehensible density. In a fraction of a second, it began expanding in volume, and it’s still continuing to do so today. So how old is the Universe? How long has it been expanding for? How do we know? For a good long while, Astronomers assumed the Earth, and therefore the Universe was timeless. That it had always been here, and always would be. In the 18th century, geologists started to gather evidence that maybe the Earth hadn't been around forever. Perhaps it was only millions or billions of years old. Maybe the Sun too, or even… the Universe. Maybe there was a time when there was nothing? Then, suddenly, pop… Universe. It’s the science of thermodynamics that gave us our first insight. Over vast lengths of time, everything moves towards entropy, or maximum disorder. Just like a hot coffee cools down, all temperatures want to average out. And if the Universe was infinite in age, everything should be the same temperature. There should be no stars, planets, or us. The brilliant Belgian priest and astronomer, George Lemaitre, proposed that the Universe must be either expanding or contracting. At some point, he theorized, the Universe would have been an infinitesimal point - he called it the primeval atom. And it was Edwin Hubble, in 1929 who observed that distant galaxies are moving away from us in all directions, confirming Lemaitre’s theories. Our Universe is clearly expanding. Which means that if you run the clock backwards, and it was smaller in the distant past. And if you go back far enough, there’s a moment in time when the Universe began. Which means it has an age. The next challenge… figuring out the Universe’s birthdate. In 1958, the astronomer Allan Sandage used the expansion rate of the Universe, otherwise known as the Hubble Constant, to calculate how long it had probably been expanding. He came up with a figure of approximately 20 billion years. A more accurate estimation for the age of the Universe came with the discovery of the Cosmic Microwave Background Radiation; the afterglow of the Big Bang that we see in every direction we look. Approximately 380,000 years after the Big Bang, our Universe had cooled to the point that protons and electrons could come together to form hydrogen atoms. At this point, it was a balmy 3000 Kelvin. Using this and by observing the background radiation, and how far the wavelengths of light have been stretched out by the expansion, astronomers were able to calculate how long it has been expanding for. Initial estimates put the age of the Universe between 13 and 14 billion years old. But recent missions, like NASA’s WMAP mission and the European Planck Observatory have fine tuned that estimate with incredible accuracy. We now know the Universe is 13.8242 billion years, plus or minus a few million years. We don’t know where it came from, or what caused it to come into being, but we know exactly how our Universe is. That’s a good start.

On the morning of February 15, 2013, people in western Russia were dazzled by an incredibly bright meteor blazing a fiery contrail across the sky. A few minutes later a shockwave struck, shaking the buildings and blowing out windows. 1,500 people went to the hospital with injuries from shattered glass. This was the Chelyabinsk meteor, a chunk of rock that struck the atmosphere going almost 19 kilometers per second. Astronomers estimate that it was 15-20 meters across and weighed around 12,000 metric tonnes. Here’s the crazy part. It was the largest known object to strike the atmosphere since the Tunguska explosion in 1908. Catastrophic impacts have shaped the evolution of life on Earth. Once every 65 million years or so, there’s an impact so destructive, it wipes out almost all life on Earth. The bad news is the Chelyabinsk event was a surprise. The asteroid came out of nowhere. We need to find all the potential killer asteroids, and understand what risks we face. "I’m Ned Wright…" That’s Dr. Ned Wright. He’s a professor of physics and astronomy at UCLA, and the Primary Investigator for the Wide-field Infrared Survey Explorer mission; a space telescope that looks for low temperature objects in the infrared spectrum. "I think the best way to protect the Earth from asteroids is to get out and look very assiduously to find all the hazardous asteroids. Although astronomers have been finding and cataloging asteroids for decades, we still only have a fraction of the dangerous asteroids tracked. The large continent destroyers have mostly been found, but there’s a whole class of smaller, city killers out there, and they’re almost entirely unknown. There are... these dark asteroids that may not be the most dominant part of the population but they certainly can be a very hazardous subset, it’s important to do the observations in the infrared. So you actually, instead of looking for the ones that reflect the most light, you look for the ones that have the biggest area and therefore the ones that are the heaviest and can do the most damage. And so, I think that an infrared survey is the way to go." "In the infrared wavelengths, we can find these objects because they’re large, not because they’re bright. And to really do this right, we need a space-based infrared observatory capable of surveying vast areas of the sky, searching for anything moving." The WISE mission has been offline for a few years, but WISE is actually being reactivated right now to look for more Near Earth Objects, so we’re currently cooled down to 93 K, and when we get to 73 K, which is where we were when we turned off in 2011 we’ll probably be able to go out and find more Near Earth Objects. Note: this interview was recorded in November, 2013. WISE resumed operations in December 23, 2013 But to really find the vast majority of dangerous asteroids, you need a specialized mission. One proposal is the Near Earth Asteroid Camera, or NEOCam because it’d be much better to have a telescope that was slightly colder than the 73 K WISE is with coolant, and you can do that by getting away from the Earth. and so the NEOcam telescope is designed to go a million and a half kilometers from the Earth and therefore it would be quite cold, about 35 K and at that temperature, it can operate longer into the infrared and do a very sensitive survey for asteroids. NEOCam is just one idea. There’s also the Sentinel proposal from B612 Foundation. It’s also an infrared survey and it would go into an orbit like Venus’ orbit, so it would be hundreds of millions of km away from Earth, but not orbiting around Venus, because that would be too hot as well and then with an infrared telescope, it would survey for asteroids. NEOCam and Sentinel would operate for years, scanning the sky in the infrared to find all of the really hazardous asteroids. You wouldn't be able to necessarily find the ones the size of the one that hit Chelyabinsk,

Dr. Andrea Ghez has spent much of her career studying the region right around the center of the Milky Way, including its supermassive black hole. In fact, she helped discover it in the first place. Dr. Ghez speaks about this amazing and dynamic region. "Hi, I'm Dr. Andrea Ghez, and I'm a professor of physics and astronomy at UCLA. I study the center of our galaxy. The original objective was to figure out if there's a supermassive black hole there, and in doing this, we've actually uncovered more questions than answers." What are you looking for at the center of the galaxy? "We are tremendously privileged to be able to study the center of the galaxy, and have this exquisite laboratory to play with, to get insight into the fundamental physics of black holes, and also their astrophysical role in the formation and evolution of galaxies. You can also ask what kinds of phenomena do you expect to see around a black hole, and we have a lot of predictions about our thoughts about how galaxies form and evolve, and our ideas suggest that there's a feedback between the galaxy and the black hole. But many of these models predict things that we simply don't see, which again provides yet another playground." What's it like around the supermassive black hole at the center of the galaxy? "If you could get into a spaceship and get right down to the black hole, it would be a very busy place. Stars would be zooming around, like the sun, but you'd have a very busy day. You wouldn't survive - I guess that would be another problem! You'd get torn apart. It's just a very extreme place. The analogy that often gets made with the center of the galaxy is that it's like the urban downtown, and we live out in the suburbs, so we live in a very calm place whereas the center of the galaxy is a a very extreme place, in almost every way you can describe an environment." What are some of the discoveries? "The observations at the center of the Milky Way have taught us that one, it's really normal to have a black hole at the center of the galaxy. I mean, our galaxy is completely ordinary, garden-variety, nothing-special-about-us, so if we have one, presumably every galaxy harbors a supermassive black hole at it's center. We've also learned that the idea that a supermassive black hole should be surrounded by a very dense concentration of very old stars is not true. And that prediction is often used in other galaxies to find their black holes, because we can't do the kinds of experiments we've done at the center of our own - that you look for this concentration of light, but in our galaxy we're not seeing that, so you have a case where's there's absolutely clearly a supermassive black hole, yet you don't see this collection of old stars. That's a puzzle. "Another puzzle that we've found that's illuminating our ideas about other galaxies is that people predicted that you shouldn't see young stars being formed near a black hole. In fact, in the early 1980's, when people recognized that there were young stars found in the vicinity of a black hole, that was used to argue that perhaps you couldn't possibly have a black hole because of these young stars. And yet again, we have a supermassive black hole - we know it, and those young stars are still exist, and we've even found stars even closer. And it's the tidal forces that make it even more difficult to understand why the young stars should be there. The tidal forces pull the gases apart, and for star formation, you need a very fragile balls of gas and dust to collapse, so something's amiss." How might those young stars get formed? "There are so many ideas about how young stars could form at the center of the galaxy, but the one that has the most support is the idea that, at the time that these stars were being formed, that there was a much denser concentration of gas than there is today, and in that denser concentration you can get the collapse of those little clouds.

Our civilization will need more power in the future. Count on it. The ways we use power today: for lighting, transportation, food distribution and even entertainment would have sounded hilarious and far fetched to our ancestors. As our technology i...

Even though the name is a little confusing, you probably already know that a light year is the distance that light travels in a full year. At speeds of almost 300,000 kilometers per second that gets you pretty far from home. So take that distance and turn it into a cube, each side one light year in length. Imagine that giant volume of space, a little challenging for some of us to get our heads around. How much “stuff” would be in there, and not just “stuff”... how much nothing is in there? There is an answer, but it all depends on where put your giant cube. Measure it at the core of the galaxy, and there are stars buzzing around all over the place. Perhaps in the heart of a globular cluster? In a star forming nebula? Or maybe out in the suburbs of the Milky Way? There’s also great voids that exist between galaxies, where there’s almost nothing. There’s no getting around the math in this one. First, let’s figure out an average density for the Milky Way and then go from there. Its about 100,000 light-years across and 1000 light-years thick. According to my buddy Phil Plait, the total volume of the Milky Way is about 8 trillion cubic light-years. And the total mass of the Milky Way is 6 x 10 to the power of 42 kilograms. Divide those together and you get 8 x 10 to the power of 29 kilograms per light year. That’s an 8 followed by 29 zeros. Is that a lot? It sounds like a lot. Actually, that’s about 40% of the mass of the Sun. In other words, on average, across the Milky Way, there’s about 40% the mass of the Sun in every cubic light year. But in an average cubic meter, there’s only about 950 attograms. Almost a femtogram; a quadrillionth of a gram of matter. Which is pretty close to nothing. Seriously, air has more than a kilogram of mass per cubic meter. In the densest regions of the Milky Way, like inside globular clusters, you can get densities of stars with 100, or even 1000 times greater than our region of the galaxy. Stars can get as close together as the radius of the Solar System. But out in the vast interstellar gulfs between stars, the density drops significantly. There are only a few hundred individual atoms per cubic meter in interstellar space. And in the intergalactic voids; the gulfs between galaxies, there are just a handful of atoms per meter. How much stuff is there in a light year? It all depends on where you look, but if you spread all the matter around by shaking the Universe up like a snow globe, the answer is very close to nothing.

Who knows what the future holds for our Sun? Dr. Mark Morris, a professor of astronomy at UCLA sure knows. Professor Morris sat down with us to let us know what we’re in for over the next few billions years. "Hi, I'm Professor Mark Morris. I'm teaching at UCLA where I also carry out my research. I work on the center of the galaxy and what's going on there - in this fabulous arena there, and on dying stars - stars that have reached the end of their lifetime and are putting on a display for us as they do so." What is the future of our sun? "Well, there's every expectation that in about 5 billion more years, that our sun will swell up to become a red giant. And then, as it gets larger and larger, it will eventually become what's called an asymptotic giant branch star - a star whose radius is just under the distance between the sun and the Earth - one astronomical unit in size. So the Earth will be literally skimming the surface of the red giant sun when it's an asymptotic giant branch star." "A star that big is also cool because they're cold - red hot versus blue hot or yellow hot like our sun. Because it's cold, a red giant star at its surface layers can keep all of its elements in the gas phase. So some of the heavier elements - the metals and the silicates - condense out as small dust grains, and when these elements condense out as solids, then radiation pressure from this very luminous giant star pushes the dust grains out. That may seem like a minor issue, but in fact these dust grains carry the gas with them. And so the star literally expels its atmosphere, and goes from a red giant star to a white dwarf, when finally the core of the star is exposed. Now, as it's doing this, that hot core of the star is still very luminous and lights up through a fluorescent process, this out-flowing envelope, this atmosphere that was once a star, and that's what produces these beautiful displays that are called planetary nebulae." "Now, planetary nebulae can be these beautiful round, spherical objects, or they can be bipolar, which is one of the mysteries that we're working here is trying to understand why, at some stage, a star suddenly becomes axisymmetric - in other words, is sending out is's atmosphere in two diametrically opposed directions predominantly, rather than continuing to lose mass spherically." "We can't invoke rotation of the star - that would be one way to get a preferred axis, but stars don't rotate fast enough. If you take the sun and let it expand to become a red giant, then by the conservation of angular momentum, it literally won't be spinning at all. It'll be spinning so slowly that it'll literally have no effect. So we can't invoke spin, so there must be something going on deep down inside the star, that when you finally expose some rapidly spinning core, it can have an effect." "Or, all of the stars that we see as planetary nebula can have binary companions, that could be massive planets or relatively low mass stars that themselves can impose an angular momentum orientation on the system. This is in fact an idea that I've been championing for decades now, and it has some traction. There's a lot of planetary nebula nuclei, the white dwarves, that seem to have companions near them that are suspect for having been responsible for helping strip the atmosphere of the mass-losing red giant star but also providing a preferred axis along which the ejected matter can flow."

The Universe is always surprising us with how little we know about... the Universe. It’s continuously presenting us with stuff we never imagined, or even thought possible. The search for extrasolar planets is a great example. Since we started, astronomers have turned up over a thousand of them. These planets can be gigantic worlds with many times the mass of Jupiter, all the way down to little tiny planets smaller than Mercury. Astronomers are also finding one type of world that feels both familiar and yet totally alien... the super earth. In the strictest sense, a super earth is just a planet with more mass than Earth, but less than a larger planet like Uranus or Neptune. So, you could have super earths made of rock and metal, or even ice and gas. These planets could have oceans and atmospheres, or made of nothing but hydrogen and helium. The goal, of course, is to find a rocky super earth located in the habitable zone. This is the region where the planets are the right distance from the star for liquid water to be present. The first discovery of a potentially habitable super earth was in the star system Gliese 581. Here, astronomers found 2 planets orbiting within the habitable zone. Gliese 581 c has a mass of 5 times the Earth, and orbits on the overly warm side of the habitable zone and, Gliese 581 d is 7.7 times the mass of the Earth, and is on the cold side of the zone. We've now found dozens of super earths. One recent discovery, Kepler 11-b, has only 4 times the mass of the our planet and just 1.5 times its size. You’re probably wondering about the gravity. The exact gravity depends on the ratio of the planet’s size to its mass. If you could stand on the surface of a super earth, you’d probably feel a higher gravity. Considering these planets can have 5 or more times the mass of Earth. But less gravity than you’d expect. An increase in size makes a big difference. For example, if you could stand on the surface of Kepler 11-b, which is about 1.5 times bigger but a whopping 4 times more massive, you’d feel only 1.4 times the pull of Earth’s gravity. Here’s the big question. Could a super earth support life? Aquatic life would be no problem. Once you’re in the ocean, the effects of gravity are balanced out by the buoyancy of water. How well life could survive on land and in the air depends on the gravity of the world. With higher gravity, plants and animals wouldn't be able to grow as tall. Animals would need thicker legs to support their weight. If the atmosphere was denser, likely because of the higher gravity, flying creatures could move more slowly with larger wingspans. If intelligent life does develop on a heavy gravity world, it will have a much harder time getting into space. Reaching orbital velocity is already tremendously difficult from Earth. Just imagine how much more difficult it would be to launch rockets if everything was twice as heavy. So, a big thank you to the astronomers showing us that there are all kinds of crazy worlds out there. I just wish they weren't so far away.

I’m Fraser Cain, and I’m a sailor. Well, okay, I've got a sailboat that I take out on the water when its warm and the weather’s nice here on Vancouver Island. I think it’s one of the reasons I absolutely love the idea of a solar sail. Here’s how they work: Light is made up of photons. Even though they have no mass at rest, they have momentum when they’re moving, well, light speed. When they reflect off a surface, like a mirror or a shiny piece of metal, they impart some of this momentum to that surface. This effect is negligible here on Earth, but out in space, with forces perfectly in balance, that additional momentum can really add up. A spacecraft flying to Mars gets pushed off course by several thousand kilometers because of light pressure from the Sun.If mission planners didn't compensate for this drift, their spacecraft would miss the planet, or even worse, crash into it. Even though the total amount of pressure per square meter on a solar sail is minuscule, it’s constantly streaming from the Sun, and it’s totally free....And propulsion that you don’t have to carry with you is the best kind there is. This is more than just an idea. Solar sails have already been launched and deployed in space. The Japanese Ikaros satellite unfurled a 14-meter solar sail back in 2010. NASA launched its own Nanosail-D spacecraft in 2011. An even bigger solar sail, the Sunjammer, is planned for launch in 2014. The Planetary Society is working on a solar sail project as well. The closer to the Sun you are, the better they work. In fact, a solar sail would be an ideal vehicle to explore the regions of Mercury and Venus, since they receive so much radiation. But you’re probably wondering how a solar sail could get down to those planets because light is streaming from the Sun in all directions. It’s all about raising and lowering your orbit. If you want to raise your orbit around an object, all you have to do is speed up. And if you want to lower your orbit, you just need to slow down. A solar sail launched from Earth would start out with the same orbital velocity around the Sun as the Earth. To get into a higher orbit, it tilts the sail so that the light from the Sun speeds it up. And to get into a lower orbit, it tilts in the opposite direction, and the light from the Sun acts like a brake. A solar sail might even be the ideal spacecraft to make the journey to another star. An interstellar solar sail could lower its orbit so that it’s just above the surface of the Sun. Then, it would unfurl the full sail and capture the most possible photons. A series of powerful laser beams would then target the sail and increase its velocity to a significant fraction of the speed of light. Of course, you’d need a solar sail thousands of kilometers across, made of a material thinner than a human hair, and lasers putting out more energy than all of humanity. The idea is still intriguing, even though it’s well outside our current technology. Once this technology gets better tested, we’ll to see many more missions employ solar sails as part of their propulsion system.