Universe Today Video

We're familiar with the sky on Tatooine with its twin suns. But could a planet actually orbit two stars at the same time? Could you have a planet in a multiple star system with 4, 6 or more suns? Hey kids, you remember Star Wars right? Tatooine ring any bells? Lots of sand Tusken raiders walking single file. Banthas sweating all over the place like some crazy mammoth-goat breeding experiment gone horribly awry? Tatooine was an arid desert planet, it had 2 suns and 3 moons. It’s not the only fictional planet to orbit multiple suns. In Nightfall by Isaac Asimov, planet Lagash had 6 suns. Could something like this be possible? Interestingly, most stars in the Milky Way are in multiple star systems. You can easily have double, triple, or quadruple systems. There are even star clusters with hundreds or even thousands of stars. Just imagine the crazy chaotic gravitational interactions in a multiple star system. So, could they have planets? Yes. There are circumbinary systems, where stars orbit each other their planets orbit outside, circling them both. Since the stars orbit one another so closely, it’s the gravitational equivalent of a single star. From an orbiting planet, the stars would always appear together in the sky. To date, we have discovered 17 of these systems. Then there are wide binary systems, which are far more dangerous for planets. Here the planets orbit one main star, and there’s another star which maintains a distant orbit much further out. You don’t want to live there. The gravitational interactions are chaotic and lead to mayhem. In simulations, planets which aren't tightly orbiting a star are ejected out of the system, or crashed into other planets or stars. We might already be detecting highly elliptical orbits from disrupted planets just like these. A triple star system was recently discovered in the constellation Cygnus: HD 188753. Here, a pair of stars are tightly bound, and these are in a wide binary arrangement with a sun-mass star. A planet closely orbits the primary star, but all other planets were likely ejected. In the year 2012, a planet was found around Alpha Centauri B, and PH1 was the first quadruple star system to be discovered to have a planet. Kepler 47 is a multi-star, multi-planet system. Two stars orbit one another every 7.45 days. Here, the gas giant Kepler 47c orbits the stars every 303 days and is even located in the habitable zone. This sounds like perfect concept art for a Vin Diesel film, or artwork airbrushed on the side of a van. Finally, In 2011, the Kepler-16 system was found to have a circumbinary planet in the habitable zone. So, two stars, closely orbiting each other and a Saturn-mass, Kepler 16b orbiting the two. Astronomers informally called this a real Tatooine. What do you think? Would you want to live on a desert world like Tatooine or Arrakis? Tell us your thoughts in the comments below.

It feels like you just can't get away from clingy gravity. Even separated by distances of hundreds of millions of light years, gravity is reaching out to all of us. Is there a place you could go to get away from gravity entirely? Fortunately for our space intolerant tissues and terrible oxygen dependency withdrawal symptoms, gravity binds us to our sweet, cozy home with breathable air, the Earth. Its collective mass is trying to accelerate you towards its center, that way, at 9.8 meters per second squared. But the Earth isn't the only one looking to cuddle. You’re also being pulled at by the Moon, and if it weren't for the Earth here, that pull could hurl you far off into deep space, or crash you into its cold dusty surface. In fact, as the Moon passes overhead, you’re being imperceptibly tugged upwards. This possessive tug o war isn't just between the moon, and the earth fighting over you like an older brother keeping a small doll out of reach a younger sibling. The Sun is also in on this shenanigan. Gravity from there is pulling at you from a distance of 150 million km. Well, aren't we popular. So how far would you have to go to escape this gravitational custody battle completely? Even At 2.5 million light years distance, gravity is still reaching out and being a clingy creeper. The Milky Way and Andromeda are pulling towards each other. The gravity between these two bodies is strong enough to overcome the expansion of the universe. Which will result in a galactic smash-up derby a few billion years from now. There’s no end to it. Gravity appears to be madly greedy and long armed. Members of the Virgo Super cluster are connected to each other, and they’re dozens of millions of light-years apart. Objects in the Pisces-Cetus Super cluster complex are even connected to each other by our invisible and obnoxiously possessive friend. And they are hundreds of millions of light years apart... In fact, you’re so popular that you are gravitationally pulled towards even most distant object in the observable Universe. And they, in turn, are linked to you. As a result, without the outward expansion and acceleration of the Universe, everything would fall inward to a common center of gravity. Newton thought that gravity was instantaneous and if the Sun disappeared, the Earth would immediately fly away. Einstein realized that gravity is distortions of spacetime caused by mass. And as it turns out, gravity moves at the speed of light. If the Sun disappeared, Earth would continue to follow the curved spacetime distortion for 8 whole minutes. Interactions between massive objects, like when black holes collide, cause ripples in spacetime called gravitational waves. As a gravitational wave passes through, you get warped in spacetime, like a wave in the water. The amount is so slight we've never seen them directly. However, the decay of pulsar orbits have shown them indirectly. The ground-based LIGO experiment might someday detect a gravitational wave, but there’s been no luck so far. The Space-based LISA experiment should detect gravitational waves with more precision. The first version will launch in 2015, but the real experiment probably won’t be operational until 2030. Everybody wants a piece, and I don’t know about you, I just want to be left alone. Gravity’s is reach is amazingly far. It’s everywhere, all the time, and it’s having none of that. What do you think? If you had the power to remove yourself from Gravity’s pull, what would you do? Tell us in the comments below.

In a Universe that's expanding apart, isn't it strange that Andromeda is actually drifting towards us? Dr. Thad Szabo from Cerritos College explains why this is happening. "I'm Thad Szabo, and I teach astronomy and physics at Cerritos College." Is Andromeda drifting towards us? "The reason that we see Andromeda moving toward us is because it's nearby enough, and the Milky Way is massive enough and Andromeda is massive enough that they're gravity is strong enough that there is not enough space between them that the space was able to expand and push them apart against the force of gravity. So if you take the Milky Way, all of its stars and all of its gas and dust, all of its dark matter, you're looking at something that's a trillion times the mass of the sun. You have the same for Andromeda, and they're less than a mega parsec apart - to Andromeda, its about 2.2 billion light years. And so with that distance and that much mass, that's close enough that gravity is drawing them together. Most galaxies, because they're so distant, you do see them moving away due to the expansion of the universe." "But actually M81, which is about 12 million light years away, is also moving towards the Milky Way. It's the most distant galaxy that doesn't show red shift. So there's enough gravity in this local group - I guess the local group is typically the Milky Way galaxy, the Andromeda galaxy, the Triangulum galaxy, and however many tens of dwarf galaxies that we've either discovered or haven't discovered yet. But there's also a bubble of about ten to twenty major size galaxies extending out to about fifteen million light years or so, and that's kind of right on the border between where the expansion of the universe would drive things apart and where the gravity is strong enough to hold things together."

Spiral galaxies get their name because of their beautiful spiral shape and iconic arms. But why do galaxies have these spiral shapes, and what causes the arms? Galaxies are some of the most beautiful and inspiring structures in the Universe. As you know, they aren’t solid disks, they’re a gigantic spill of individual stars webbed together by gravity. There are a few rough fundamental shapes that a galaxy can have, and the bulk of these are some variation of a spiral. Each one with twisting arms of stars reaching tens of thousands of light years in every direction along a plane, out from a galactic core. So what gives them this characteristic spiral shape? Earliest galaxies didn't have clearly defined spiral arms. They were either two-armed or, had thick irregular chaotic woolly arms with star forming clumps. After 3.6 billion years, however, the chaos had settled down into the shapes we see today. But it took until the Universe was 8 billion years old for these modern multi-armed spirals, like the Milky Way or Andromeda to appear. So where did they come from? These arms are in fact density waves passing through the galaxy, with stars moving in and out of the waves. The arms themselves aren't permanent structures made of the same clumps of stars. Imagine driving down a highway and people are slowing down to gape slack-jawed a crashed alien saucer. Cars will slow down as they reach the saucer and form a clump, and then the car in the lead of the clump will accelerate and proceed down the highway as other cars progress through the clump to take their place. This is a great analogy for movement in a galaxy. As a density wave approaches, stars accelerate towards it. Then they slow down as they move away from it. Just like a comet falling into the gravity well of the Sun. And when the density wave moves through an area, it kicks off an era of star formation. So the material of the galaxy is being constantly stirred and new stars are born as a density wave makes its way through the galaxy. When you picture this, keep in mind that stars closer to the core of the galaxy orbit faster than the spiral arm, and the stars further out go more slowly. Our galaxy, the Milky Way takes about 240 million years to complete a full rotation. But we pass through a major spiral arm every 100 million years or so, remaining in the higher density region for about 10 million years. Astronomers have only recently figured out why these arms exist in the first place. Originally, they suspected it might be like a garden sprinkler, with material fountaining out from the center of the galaxy, or channeled by magnetic fields. They also thought that the arms might be transient features. Appearing and disappearing over time. But new evidence and simulations show they’re long lasting, they believe the arms themselves form as a result of giant molecular clouds of hydrogen. These clouds initiate the arms and keep the shape sustained over billions of years. What do you think? What’s your favorite spiral galaxy? Tell us in the comments below.

When you look into the night sky, you’re seeing tremendous distances away, even with your bare eyeball. But what’s the most distant object you can see with the unaided eye? And what if you get help with a pair of binoculars, a telescope, or even with the Hubble Space Telescope. Standing at sea level, your head is at an altitude of 2 meters, and the horizon appears to be about 3 miles, or 5 km away. We’re able to see more distant objects if they’re taller, like buildings or mountains, or when we’re higher up in the air. If you get to an altitude of 20 meters, the horizon stretches out to about 11 km. But we can see objects in space which are even more distant with the naked eye. The Moon is 385,000 km away and the Sun is a whopping 150 million km. Visible all the way down here on Earth, the most distant object in the solar system we can see, without a telescope, is Saturn at 1.5 billion km away. In the very darkest conditions, the human eye can see stars at magnitude 6.5 or greater. Which works about to about 9,000 individual stars. Sirius, the brightest star in the sky, is 8.6 light years. The most distant bright star, Deneb, is about 1500 light years away from Earth. If someone was looking back at us, right now, they could be seeing the election of the 52nd pope, St. Hormidas, in the 6th Century. There are even a couple of really bright stars in the 8000 light year range, that we might just barely be able to see without a telescope. If a star detonates, we can see it much further away. The famous 1006 supernova was the brightest in history, recorded in China, Japan and the Middle East. It was a total of 7,200 light years away and was visible in the daytime. There’s even large structures we can see. Outside the galaxy, the Large Magellanic Cloud is 160,000 light years and the Small Magellanic Cloud is almost 200,000 light years away. Unfortunately for us up North, these are only visible from Southern Hemisphere.The most distant thing we can see with our bare eyeballs is Andromeda at 2.6 million light years, which in dark skies looks like a fuzzy blob. If we cheat and get a little help, say with binoculars - you can see magnitude 10 - fainter stars and galaxies at more than 10 million light-years away. With a telescope you can see much, much further. A regular 8-inch telescope would let you see the brightest quasars, more than 2 billion light years away. Using gravitational lensing the amazing Hubble space telescope can see galaxies, incredibly far out, where the light had left them just hundreds of millions of years after the Big Bang. If you could see in other wavelengths, you could see different distances. Fortunately for our precious radiation sensitive organs, Gamma and X rays are blocked by our atmosphere. But if you could see in that spectrum, you could see objects exploding billions of light years away. And if you could see in the radio spectrum, you’d be able to see the cosmic microwave background radiation, surrounding us in all directions and marking the edge of the observable universe. Wouldn't that be cool? Well, maybe we can… just a little. Turn on your television, some of the static on the screen is this very background radiation, the afterglow of the Big Bang. What do you think? If you could see far out in the Universe what would you like a close up view of? Tell us in the comments below.

Space is a hostile environment for human beings. No part of it will permit you to survive longer than a minute. But what's the fastest way to die in space? Just in case you were planning to jump out into the vacuum of space without a spacesuit, I urge you to reconsider. There’s nothing but painful suffocation and death. Do not do it. You probably wouldn't be here if you weren't wondering, just how lethal is space? What are all the ways space is trying to kill you? Space has a Swiss army knife of methods to do you in. You won’t be surprised to learn that classic sci-fi usually had it wrong. If you jumped out into the cold deep void without a protective suit, you wouldn't pop like a giant pressurized juicy meat pimple. Your blood doesn't boil, and you don’t flash freeze. The good news is even though there is a pressure difference, human skin is strong enough to keep your body together. The bad news is you just plain old asphyxiate, almost instantaneously. The human body has about 15 seconds of usable oxygen in the blood. Once you run through that oxygen, you’ll take a quick space nap and then die a few minutes later. On Earth, you can hold your breath for a few minutes but this gets much harder in space, as the low pressure forces the air out of your lungs. In fact, it would probably be wise to breathe every last bit of air out before you stepped out, since it’s coming out violently, one way or another. Here's the amazing thing. If you jumped out into space and could get back into a pressurized environment within a minute or so, you probably wouldn't suffer any permanent damage, aside from a little bruising, some hypothermia and a really nasty sunburn. Stay out for any longer, though, and the damage will get worse. Beyond a few minutes and you’ll be done.Which is just fine, as you weren't planning on going out into space without a spacesuit anyway. Unfortunately, even tucked safely in your spacecraft, there are tremendous risks to being away from the comfort of Earth. You've got to be worried about radiation. Once a spacecraft leaves the protection of the Earth’s magnetic field, it’s exposed to the high levels constantly streaming through space. A trip from Earth to Mars and back again might increase your overall risk developing a fatal cancer by about 5%, and that’s a risk most astronauts are willing to take. But there are solar storms blasting out from the Sun that could deliver a lethal dose of radiation in just a few hours. Astronauts would need a safe, radiation-shielded location during these solar storms or they’d expire from acute radiation poisoning. There are many, many other risks from traveling in space. Fire is one of the worst, failure of your oxygen system, access to clean water and food become an obvious problem. Even things we usually don’t think about, like mold building up in the damp environment of a spaceship becomes a problem. Survive all these immediate hazards, just like here on Earth, and the long term hazards will get you. We have no idea if it’s even possible for the human body to exist in microgravity for longer than a few years. Your bones dissolve, your muscles waste away, and there might be other consequences. So far, nobody is willing to run the experiment long enough to find out. And finally, the fastest way space can kill you is likely impact with debris. Even though space is mostly empty, there’s all kinds of material whizzing around. Every spacecraft is pockmarked with micrometeorite impacts. There are holes punched through the International Space Station’s solar panels. These tiny pieces of rock can be traveling at 10 kilometers per second when they impact the spacecraft. Spacecraft have layers of protection to absorb smaller particles, but there’s no way to prevent larger objects from causing catastrophic damage. If those layers weren't there you’d be a short hop skip and a jump from becoming a heavily perforated spongebob spacepants.

Emily Lakdawalla from the planetary society describes one of the mysteries that's currently fascinating her. There are strange structures on Mercury which have been called "hollows". What might they be? "My name is Emily Lakdawalla - I'm the senior editor and planetary evangelist for the Planetary Society." What are the hollows on Mercury? "Well, the Messenger mission has been mapping and orbiting Mercury and they've discovered these new kinds of features that nobody had ever seen before that they were calling hollows - they're these pits in the ground, but they're not impact craters. They look like somewhere where something has evaporated. They look like Swiss cheese - like that terrain at the south pole of Mars where the carbon dioxide cap is evaporating. They look kind of the same, except that this is mercury - there's no carbon dioxide or water ice. It's all gotta be solid rock." "So what exactly is evaporating to create these holes and how it's disappearing from the ground is still a complete mystery. And the Messenger missions - they're following up on the high-resolution imaging, but they still don't have good info for what those hollows are." Are they similar to the caves on the Moon and Mars? "The caves that have been found on the moon and Mars are likely skylights into lava tubes. There's vulcanism all over the solar system - that's how most of the surfaces of most of the surfaces of most of the planets were built - with lava spewing out. And wherever you have lava, you've got often a solid surface on the top and then liquid lava running underneath the surface. Eventually that drains and you get a hollow tube, and then maybe an earthquake happens or something opens a skylight down into the tube. So we've found cave skylights on both the moon and Mars, and of course on Earth. I don't know that we've found any of these on Mercury - I don't think we have."

Since black holes are the most powerful gravitational spots in the entire Universe, can they distort light so much that it actually goes into orbit? And what would it look like if you could survive and follow light in this trip around a black hole? I had this great question in from a viewer. Is it possible for light to orbit a black hole? Consider this thought experiment, first explained by Newton. Imagine you had cannon that could shoot a cannonball far away. The ball would fly downrange and then crash into the dirt. If you shot the cannonball harder it would fly further before slamming into the ground. And if you could shoot the cannonball hard enough and ignore air resistance - it would travel all the way around the Earth. The cannonball would be in orbit. It’s falling towards the Earth, but the curvature of the Earth means that it’s constantly falling just over the horizon. This works not only with cannonballs, astronauts and satellites, but with light too. This was one of the big discoveries that Einstein made about the nature of gravity. Gravity isn't an attractive force between masses, it’s actually a distortion of spacetime. When light falls into the gravity well of a massive object, it bends to follow the curvature of spacetime. Distant galaxies, the Sun, and even our own Earth will cause light to be deflected from its path by their distortion of spacetime. But it’s the incredible gravity of a black hole that can tie spacetime in knots. And yes, there is a region around a black hole where even photons are forced to travel in an orbit. In fact, this region is known as the “photon sphere”. From far enough away, black holes act like any massive object. If you replaced the Sun with a black hole of the same mass, our Earth would continue to orbit in exactly the same way. But as you get closer and closer to the black hole, the orbiting object needs to go faster and faster as it whips around the massive object. The photon sphere is the final stable orbit you can have around a black hole. And only light, moving at, well, light speed, can actually exist at this altitude. Imagine you could exist right at the photon sphere of a black hole. Which you can’t, so don’t try. You could point your flashlight in one direction, and see the light behind you, after it had fully orbited the black hole. You would also be bathed in the radiation of all the photons captured in this region. The visible light might be pretty, but the x-ray and gamma radiation would cook you like an oven. Below the photon sphere you would see only darkness. Down there is the event horizon, light’s point of no return. And up above you’d see the Universe distorted by the massive gravity of the black hole. You’d see the entire sky in your view, even stars that would be normally obscured by the black hole, as they wrap around its gravity. It would be an awesome and deadly place to be, but it’d sure beat falling down below the event horizon. If you could get down into the photon sphere, what kind of experiments would you want to do? Tell us in the comments below.

Have you heard the terrifying news that the Earth's poles are going to flip? What does "flipping" mean? And if the Earth's poles do flip, are we in any danger? Have you heard the startling news that the Earth’s poles might flip? Perhaps in the response to a close pass from the mysterious Planet X? Are you imagining the entire Earth actually flipping over on its side or rotating upside down, possibly while Yakkity Sax plays in the background? When will this happen? Can this happen? First, there’s no secret planet hurtling through the Solar System causing chaos and orbital disturbances. So could the Earth spontaneously physically flip over? Some planets have already been tilted and flipped. Take a look at Uranus. Its orbital tilt is 98-degrees. We assume the planet started with the same tilt as the rest of the Solar System, and some event in the ancient past caused it to fall over. It could have collided with another planet, billions of years ago, or gravitational interactions with other giant planets pushed it over. And then there’s Venus, its axial tilt is 177-degrees. That’s essentially upside down. Venus is turning in the opposite direction from every other planet in the Solar System. Standing on the surface of Venus, you would see the Sun rise in the West and set in the East. Astronomers don’t know why this happened, perhaps it was gravitational interactions or a collision with another planet. To actually flip a planet off its axis would take an event so catastrophic that it would devastate the planet. Don’t worry, as far as we know, those kinds of events and interactions stopped happening billions of years ago. That’s the good news. The Earth isn't likely to just fall over, or get bashed on its side like an office tower under the might of Godzilla Now what about those magnetic poles. On Earth, they can and do reverse on a regular basis. The Earth is often shown like a giant bar magnet, with a north magnetic pole and a south magnetic pole. Over vast periods of time, the Earth’s north pole becomes its south pole, and vice versa. Geologists measure the magnetic configuration of iron particles in ancient lava flows. in one part of the lava flow, the particles oriented with one magnetic configuration, and then in another, the particles were reversed. It turns out the planet reverses its polarity every 450,000 years, and the last reversal happened about 780,000 years ago. Which means it could happen in the next few thousand years. If the Earth’s poles did reverse, what would happen to us? If the magnetic field disappeared entirely, the planet would be bathed in radiation from the Sun, which would likely cause an increase in cancer. But the Earth’s atmosphere would still protect us from majority of radiation. What about mass extinctions? Scientists have wondered if there’s a link between them and magnetic reversals. Fortunately for us, there doesn't seem to be any connection. Whenever geomagnetic reversals happened in the past, it didn't devastate life on Earth. So don’t worry about it. There is a pretty good chance it won’t happen in our lifetime, and maybe not for hundreds of thousands of years. And even if the Earth’s poles flip, it wouldn't be the end of the world. You might need to take a sharpie to your compass though.

Every few dozen million years there's a devastating event on Earth that kills nearly all the living creatures on our planet. Dr. Michael Habib explains how life always finds a way of recovering. "Hello, my name is Michael Habib, and I'm an assistant professor of Cell and Neurobiology at the University of Southern California. I'm a biomechanist and paleontologist." How does life survive a mass extinction? "One of the most amazing things about life on earth is that if you don't kill EVERYTHING, it will eventually recover. Extinction is forever - if you kill a group, you'll never have that group again, but what we find is that often the same ecologies show up again after a major extinction, because other groups end up diversifying to do the same things as groups we'd seen elsewhere." "So the world doesn't end up looking entirely different after a mass extinction, although it would be quite different in a lot of ways. And even the great End Permian extinction killed about 99 percent of all species, or at least all the ones we can measure in the fossil record, and left that one percent, that's all it takes to eventually recover." "Now, I imagine if you took a time machine to the first six months of the Triassic, it would be a very lonely, kinda ugly world. You'd notice that animals and plants were missing. The massive extinction affected all sorts of organisms.But, at the scales we're looking at in the geologic record - tens of millions of years, a time span that's pretty much unfathomable to human experience, you can eventually recover that diversity, with speciation event after speciation event kicks in and eventually creates a new diversity." "But after each mass extinction event, the world looks a bit different. You know, if I were to drop you in a time machine before the End Permian extinction, you'd notice a lot of things different about the world. You'd notice strange large mammal-like reptiles with large saber teeth running around as the large terrestrial organisms. You would see a few of the major groups of vertebrates that exist today, especially marine, but a lot of the terrestrial groups would be very different." "If I jump to after the End Permian extinction, enough that life had recovered, you'll see those ancestors to dinosaurs, those terrasaurs, would show up in the mid to late Triassic. Then you start to see some plant groups that look more familiar to us, like plants that look a little bit more like modern conifers, things like that. So the world would definitely look different, but life does go on."

Come on Betelguese, explode already. Or maybe it'll be Eta Carinae. Which of the billions of stars in the galaxy can we count on to explode next, and when? When a new supernova is discovered, we can take that as a reminder that we live in a terribly hostile Universe. Sometimes stars just explode, and devastate a corner of a galaxy. On average, a supernova goes off twice a century in a galaxy the size of the Milky Way. Since there are potentially hundreds of billions of galaxies out there, dozens of supernovae are detonating every second in the observable Universe. The last bright supernova was SN 1987A, located in the Large Magellanic Cloud, about 168,000 light years away. Even though it was far, it exploded with so much energy it was visible to the unaided eye. That one wasn’t even in our galaxy. The Milky Way’s most recent supernova that we know of was G1.9+0.3, recently confirmed by the Chandra X-Ray Observatory. It would have been visible from Earth about 100 years ago, but it was located in the dusty regions of the Milky Way and obscured from our view. The last bright supernova was discovered in 1604 by the astronomer Johannes Kepler. This was a naked-eye supernova, in fact, at its peak, it was brighter than any other star in the night sky and for a few weeks it was even visible during the day. So, which star is likely to explode next? Can we even know that? We can, and there are even likely candidates. There’s Betelgeuse, the red supergiant star located in the constellation of Orion, only 640 light-years from Earth. Betelgeuse is massive, and it’s only been around for 10 million years. It will likely explode within a million years. Which, in astronomical time, is just before lunch. Another candidate is Eta Carinae, located about 8,000 light years from us. This blue supergiant has roughly 120 times the mass of the Sun, and it’s ready to explode in the next few hundred thousand years. Which, from the Universe’s perspective is any moment now. The closest star that could go supernova is most likely Spica, a short 240 light-years from Earth. Spica has several times the mass of the Sun, it shouldn't go off for a few million years yet. According to Phil Plait, the Bad Astronomer, another candidate is the star IK Pegasus A at just 150 light-years away. If any of these supernovae do go off, they’ll be incredibly bright. Supernova Betelgeuse would be visible during the day, it might even brighter than the full Moon. It would shine in the sky for weeks, possibly months before fading away. These explosions are destructive, releasing a torrent of gamma radiation and high energy particles. Fortunately for us, we’re safe. You’d need to be within about 75 light years to really receive a lethal dose. Which means that even the closest supernova candidate is still too far to cause us any real harm. Which star is set to explode next? Well, in the last second, 30 supernovae just went off, somewhere in the Universe. Here in our galaxy, there should be a supernova in the next 50 years or so, but we still might not be able to see it. And if we’re really really lucky, Betelgeuse or Eta Carinae will detonate, and we’ll witness one of the most awe inspiring events in the cosmos from the safety of the front porch of our galactic suburban home. Any time now. Which star would you like to see go supernova? Tell us in the comments below!

) It's a staple of science fiction, restarting our dying star with some kind of atomic superbomb. Why is our Sun running out of fuel, and what can we actually do to get it restarted? Stars die. Occasionally threatening the Earth and its civilization in a variety plot devices in science fiction. Fortunately there’s often a Bruce Willis coming in to save the day, delivering a contraption, possibly riding a giant bomb shaped like a spaceship, to the outer proximity of our dying Sun that magically fixes the broken star and all humanity is saved. Is there any truth in this idea? If our Sun dies, can we just crack out a giant solar defibrillator and shock it back into life? Not exactly. First, let’s review at how stars die. Our Sun is halfway through its life. It’s been going for about 4.5 billion years, and in 5 billion years it’ll use up all the hydrogen in its core, bloat up as a red giant, puff off its outer layers and collapse down into a white dwarf. Is there a point in there, anywhere, that we could get it back to acting like a sun? Technically? Yes. Did you know it will only use up a fraction of its fuel during its lifetime? Only in the core of the Sun are the temperatures and pressures high enough for fusion reactions to take place. This region extends out to roughly 25% of the radius, which only makes up about 2% of the volume. Outside the core is the radiative zone, where fusion doesn't take place. Here, the only way gamma radiation can escape is to be absorbed and radiated countless times, until it reaches the next layer of the Sun: the convective zone. Here temperatures have dropped to the point that the whole region acts like a giant lava lamp. Huge blobs of superheated stellar plasma rise up within the star and release their energy into space. This radiative zone acts like a wall, keeping the potential fuel in the convective zone away from the fusion furnace. So, if you could connect the convective zone to the solar core, you’d be able to keep mixing up the material in the Sun. The core of the Sun would be able to efficiently fuse all the hydrogen in the star. Sound crazy? Interestingly, this already happens in our Universe. For red dwarf stars with less than 35% the mass of the Sun, their convective zones connect directly to the core of the star. This is why these stars can last for hundreds of billions and even trillions of years. They will efficiently use up all the hydrogen in the entire star thanks to the mixing of the convective zone. If we could create a method to break through the radiative zone and get that fresh hydrogen into the core of the Sun, we could keep basking in its golden tanning rays for well past its current expiration date. I never said it would be easy. It would take stellar engineering at a colossal scale to overcome the equilibrium of the star. A future civilization with an incomprehensible amount of energy and stellar engineering ability might be able to convert our one star into a collection of fully convective red dwarf stars. And these could sip away their hydrogen for trillions of years. Tell us in the comments on how you think we should go about it. My money is on giant ‘magic bullet’ blender” or a perhaps a Dyson solar juicer.

) The Cosmic Microwave Background Radiation is the afterglow of the Big Bang; one of the strongest lines of evidence we have that this event happened. UCLA's Dr. Ned Wright explains. "Ok, I'm Ned Wright, and I'm a professor of physics and astronomy at UCLA, and I work on infrared astronomy and cosmology." How useful is the cosmic microwave background radiation? "Well, the most important information we get is from the cosmic microwave background radiation come from, at the lowest level, is it's existence. When I started in astronomy, it wasn't 100 percent certain that the Big Bang model was correct. And so with the prediction of a cosmic microwave background from the Big Bang and the prediction of no cosmic microwave background from the competing theory, the steady state, that was a very important step in our knowledge." "And then the second aspect of the cosmic microwave background that is very important, is that it's spectrum is extremely similar to a black body. And so, by being a black body means that universe relatively smoothly transitioned from being opaque to being transparent, and then we actually see effectively an isothermal cavity when we look out, so it looks very close to a black body." "And the fact that we are moving through the universe can be measured very precisely by looking at what is called the dipole anisotropy of the microwave background. So one side of the sky is slightly hotter (about 3 millikelvin hotter) and one side of the sky - the opposite side of the sky - is slightly colder (about 3 millikelvin colder), so that means that we are moving at approximately a tenth of a percent of the speed of light. And in fact we now know very precisely what that value is - it's about 370 kilometers per second. So that's our motion, the solar system's motion, through the universe." "An then the final piece of information we're getting from the microwave background now, in fact the Planck satellite just gave us more information along these lines is measurement of the statistical pattern of the very small what I call anisotropies or little bumps and valleys in the temperature. So in addition to the 3 millikelvin difference, we actually have plus or minus 100 microkelvin difference in the temperature from different spots. And so, when you look at these spots, and look at their detailed pattern, you can actually see a very prominent feature, which is there's about a one and a half degree preferred scale, and that's what's caused by the acoustic waves that are set up by the density perturbations early in the history of the universe, and how far they could travel before the universe became transparent. And that's a very strong indicator about the universe." What does it tell us about dark energy? "The cosmic microwave background actually has this pattern on a half degree scale, and that gives you effectively a line of position, as you have with celestial navigation where you get a measurement of one star with a sextant, then you get a line on the map where you are. But you can look at the same pattern - the acoustic wave setup in the universe, and you see that in the galaxy's distribution a lot more locally. We're talking about galaxies, so it might be a billion light years away, but to cosmologists, that's local. And these galaxies also show the same wave-like pattern, and you can measure that angle at scale locally and compare it to what you see in history and that gives you the crossing line of position. And that really tells us where we are in the universe, and how much stuff there is and it tells us that we have this dark energy which nobody really understands what it is, but we know what it's doing. It's making the universe accelerate in it's expansion."

Trying to keep a low profile, to prevent the aliens from invading? Bad news. Life has actually been broadcasting our existence to the Universe for hundreds of millions of years. Have you heard these crazy plans to send signals out into deep space? What if evil aliens receive them, come steal our water, enslave, eat, and use us as guinea pigs for their exotic probulators. How we could stop these madmen from announcing our presence to the galaxy? A petition on whitehouse.gov? An all caps Facebook group? An all pusheen protest? Somebody call Reddit, they’ll know what to do. If this is a worry for you and your friends, I've got bad news, or possibly good news depending on which side you come down on. We've already been broadcasting our existence for hundreds of millions of years. If aliens wanted to know we were here, all they needed to do was look through their telescopes. We’re in a golden age of extrasolar planet discovery, recently crossing the thousand-planets-mark thanks to Kepler and other space telescopes. With all these amazing planetary candidates, our next challenge will be to study the atmospheres of these planets, searching for evidence of life. There are chemicals which are naturally occurring, like water and carbon dioxide, and there are substances that can only be present if some source is replenishing them. Methane, for example, would only last only few hundred years in the atmosphere if it wasn't for farting cows and colonies of bacteria eating dead things. If we see methane or oxygen in the atmosphere of an extrasolar planet, we’ll have a good idea there’s life there. And if we see the byproducts of an industrial civilization, like air pollution, we can pinpoint exactly where they are in their technical development. It will work for us, and that means it would work for aliens. For the first few billion years, oxygen was toxic. But then cyanobacteria evolved photosynthesis and figured out how to work with oxygen more than 2.4 billion years ago. This is known as the Great Oxidation Event. For the first billion years, all this biologically generated oxygen was absorbed by the oceans and the rocks. Once those oxygen sinks filled up, oxygen began accumulating in the atmosphere. By 500 million years ago, there was enough oxygen in the atmosphere to support the kind of breathing we do today. And this much oxygen would have been obvious to the aliens. They would have known that life had evolved here on Earth, and they could have sent out their berserker spaceships to steal our water and made us watch while they ate all our small rodents. If the aliens waited, we would have given them more signs. The Industrial Revolution began in the mid 1700's. And this time, it was humans that filled the atmosphere with the pollution of our industrial processes. Again, aliens watching the planet with their space telescopes would know the moment we became a technological civilization. In the 20th century, we harnessed the power of radio transmissions, and began sending our messages out into space. For about a hundred years now, our transmissions have been expanding into a bubble of space. And so, any aliens listening within this expanding sphere of space might have a chance of hearing us. They know we’re here, and they know some of us really like Ke$ha. And finally, for the last few decades, a few groups have tried broadcasting messages using our powerful radio telescopes directly at other stars. These messages haven’t gotten very far, but I honestly wouldn't worry. Life itself gave away our position hundreds of millions of years ago. And life will help us find other civilizations, if they’re out there. What do you think? Should we turn out the lights and pretend like we’re not home or keep on actively broadcasting our presence to the Universe? Tell us what you think we should do in the comments below.

You might be surprised to know that you're living in a very special time in the Universe. And in the far future, our descendant astronomers will wish they could live in such an exciting time Let's find out why. You might be interested to know that you are living in a unique important and special time in the age of the Universe. Our view of the night sky won’t be around forever, in fact, as we think about the vast time that lies ahead, our time in the Universe will sound very special. Astronomers figure the Universe has been around for 13.8 billion years. Everything in the entire Universe was once collected together into a singularity of space and time. And then, in a flash, Big Bang. Within a fraction of a second, the fundamental forces of the Universe came into existence, followed by the earliest types of matter and energy. For a few minutes, the entire Universe was like a core of a star, fusing hydrogen into helium. Approximately 377,000 years after the Big Bang, the entire Universe had cooled to the point that it became transparent. We see this flash of released light as the Cosmic Microwave Background Radiation. Over the next few billion years, the first stars and galaxies formed, leading to the large scale structures of the Universe. These new galaxies with their furious star formation would have been an amazing sight. It would have been a very special time in the Universe, but it’s not our time. Over the next few billion years, the Universe continued to expand. And it was during this time that the mysterious force called dark energy crept in, further driving the expansion of the Universe. We don’t know what dark energy is, but we know it’s a constant pressure that’s accelerating the expansion of the Universe. As the volume of the Universe increases, the rate of its expansion increases. And over vast periods of time, it’ll make the Universe unrecognizable from what we see today. The further we look out into space, the faster galaxies are moving away from us. There are galaxies moving away from us faster than the speed of light. In other words, the light from those galaxies will never reach us. As dark energy increases, more and more galaxies will cross this cosmic horizon, invisible to us forever. And so, we can imagine a time in the far future, where the Cosmic Microwave Background Radiation has been stretched away until it’s undetectable. And eventually there will be a time when there will be no other galaxies visible in the night sky. Future astronomers will see a Universe without a cosmological history. There will be no way to know that there was ever a Big Bang, that there was ever a large scale structure to the Universe. So how long will this be? According to Dr. Lawrence Krauss and Robert J. Scherrer, in as soon as 100 billion years, there will be no way to see other galaxies and calculate their velocity away from us. That sounds like a long time, but there are red dwarf stars that could live for more than a trillion years. We will have lost our history forever. Cherish and make the most of these next hundred billion years. Keep our history alive and remember to tell our great great grandchildren and their robotic companions the tales of a time when we knew about the Big Bang. What about you? What would you go see if you could witness any astronomical event in the history of the universe?