Universe Today Video

Black holes are the most exotic and awe inspiring objects in the Universe. Take the mass of an entire star. Compress it down into an object so compact that the force of gravity defies comprehension. Nothing, not even light, can escape the pull of gravity from a black hole. The idea was first conceived in the 18th century by the geologist John Mitchell. He realized that if you could compress the Sun down by several orders of magnitude, it would have gravity so strong that you’d need to be going faster than the speed of light to escape it. Initially, black holes were considered nothing more than abstract mathematical concepts; even Einsten assumed they didn’t actually exist. But in 1931, the astronomer Chandrasekhar calculated that certain high mass stars might be able to collapse into black holes after all. They turned out to be real, and over the next few decades, astronomers found many examples out in the Universe. Stars are held in perfect balance by two opposing forces. There’s the inward pressure of gravity, attempting to collapse the star, counteracted by the outward pressure of the emitted radiation. At the core, millions of tonnes of hydrogen are being converted into helium every second, releasing gamma radiation. This fusion process is an exothermic reaction, meaning it releases more energy than it requires. As the star consumes the last of its hydrogen, it switches to the stockpiles of helium that it has built up. After it runs out of helium, it switches to carbon, and then oxygen. Since the star continues to pump out radiation, it balances out the gravitational forces trying to compress it. Stars with the mass of our Sun pretty much stop there. Not massive enough to continue the fusion reaction, beyond oxygen, they become a white dwarf and cool down. But for stars with about 5 times the mass of our Sun, the fusion process continues further up the periodic table to silicon, aluminum, potassium, and so on, all the way to iron. No energy can be produced by fusing iron atoms together. It’s the stellar equivalent of ash. And so, in a fraction of a second, the radiation from the star turns off. Without that outward pressure from the radiation, gravity wins out and the star implodes. An entire star’s mass collapses down into a smaller and smaller volume of space. The velocity you would need to escape from the star goes up, until not even light is going fast enough to escape. And this is how you form a black hole. Well, that’s the main way. You can also get black holes when dense objects, like neutron stars, collide with one another. And then there are the supermassive black holes at the heart of every galaxy. And to be honest, astronomers still don’t know how those monsters formed.

We’re in the middle of Summer here on Vancouver Island, the Sun is out, the air is warm, and the river is great for swimming. Three months from now, it’s going to be raining and miserable. Six months from now, it’s still going to be raining, and maybe even snowing. No matter where you live on Earth, you experience seasons, as we pass from Spring to Summer to Fall to Winter, and then back to Spring again. Why do we have variations in temperature at all? What causes the seasons? If you ask people this question, they’ll often answer that it’s because the Earth is closer to the Sun in the summer, and further in the winter. But this isn’t why we have seasons. In fact, during Winter in the Northern Hemisphere, the Earth is actually at the closest point to the Sun in its orbit, and then farthest during the Summer. It’s the opposite situation for the Southern hemisphere, and explains why their seasons are more severe. So if it’s not the distance from the Sun, why do we experience seasons? We have seasons because the Earth’s axis is tilted. Consider any globe you’ve ever used, and you’ll see that instead of being straight up and down, the Earth is at a tilt of 23.5-degrees. The Earth’s North Pole is actually pointed towards Polaris, the North Star, and the south pole towards the constellation of Octans. At any point during its orbit, the Earth is always pointed the same direction. For six months of the year, the Northern hemisphere is tilted towards the Sun, while the Southern hemisphere is tilted away. For the next six months, the situation is reversed. Whichever hemisphere is tilted towards the Sun experiences more energy, and warms up, while the hemisphere tilted away receives less energy and cools down. Consider the amount of solar radiation falling on part of the Earth. When the Sun is directly overhead, each square meter of Earth receives about 1000 watts of energy. But when the Sun is at a severe angle, like from the Arctic circle, that same 1000 watts of energy is spread out over a much larger area. This tilt also explains why the days are longer in the Summer, and then shorter in the Winter. The longest day of Summer, when the Northern Hemisphere is tilted towards the Sun is known as the Summer Solstice. And then when it’s tilted away from the Sun, that’s the Winter Solstice. When both hemispheres receive equal amounts of energy, it’s called the Equinox. We have a Spring Equinox, and then an Autumn Equinox, when our days and night are equal in length. So how does distance from the Sun affect us? The distance between the Earth and has an effect on the intensity of the seasons. The Southern Hemisphere’s Summer happens when the Earth is closest to the Sun, and their winter when the Earth is furthest. This makes their seasons even more severe. You might be interested to know that the orientation of the Earth axis is actually changing. Over the course of a 26,000 year cycle, the Earth’s axis traces out a great circle in the sky. This is known as the precession of the equinoxes. At the halfway point, 13,000 years, the seasons are reversed for the two hemispheres, and then they return to original starting point 13,000 years later. You might not notice it, but the time of the Summer Solstice comes earlier by about 20 minutes every year; a full day every 70 years or so. I hope this helps you understand why the Earth - and any planet with a tilted axis - experiences seasons.

As long as humans survive, we will likely be increasing our energy consumption. We want better transportation, faster computers, and stuff we just can’t imagine yet. That’s going to take energy, and lots of it. If you plot our overall use since the industrial era, you can see it’s a line that just goes up and up. There will come a time in the future when we’ve exhausted all the fossil and nuclear fuels. And once we’ve harvested as much wind, solar and geothermal energy as our planet can produce, we’re going to need to move out into space and collect energy directly from the Sun. We will construct larger and larger solar arrays, beaming the energy back to Earth. Inevitably, we’ll enclose the entire Sun in a cloud of solar satellites, allowing us to make use of 100% of the radiation it's emitting. This is a Dyson sphere. The concept was developed as part of a research paper in 1960 by the physicist Freeman Dyson. In a thought experiment, he assumed that the power needs for civilizations never stops increasing. If our descendents could actually figure out how to enclose our star in a rigid shell, we’d have 550 million times more surface area than Earth has right now, and generate 384 yottawatts of energy. Sounds great, lots of living space and free energy. But there are a host of problems. There wouldn’t be any gravity to keep anything stuck to the surface of sphere - it would all drop down towards the star and be destroyed. The sphere would be free floating in space, and unless you could keep it balanced in relation to the star, it would eventually collide with it. Finally, there might not be enough material to build a shell. This advanced civilization would need to make use of all our planets, asteroids and comets. In fact, even if you dismantled everything in the Solar System, you’d only have enough to build a shell about 15 cm-thick. The physical strength of this material would have to be immense; otherwise the sphere itself would just implode and collapse into the star. Dyson himself freely admitted that the idea of a rigid shell surrounding a star is unfeasible. Instead, he and others have proposed that civilizations would probably build a dense swarm of objects on independent orbits around their star - a Dyson cloud, or maybe a Dyson ring. Each solar satellite would be stable on its own, and capable of beaming its energy back to some planet. You could also build a cloud of solar sails. These objects would be held in perfect balance between the gravity pulling them inward, and the light pressure from the Sun pushing them outward. They wouldn’t need to orbit at all to maintain a static distance from the Sun. A full Dyson Sphere is probably impossible, but if we assume that alien civilization’s energy needs will continue to grow like ours, it makes sense to search the galaxy for megastructures. Just in case. Even though the shell would absorb the light and high energy radiation from the star, it would still emit infrared radiation which would be detectable in our telescopes. Even a partial Dyson cloud would give off a telltale light signature as it obscured the light from a star. This gives us yet another way we could search for extraterrestrial civilizations. And if we did find a full Dyson sphere, out there in the Milky Way. Well, let’s just hope they’re nice aliens.

Have you heard there’s a giant planet in the Solar System headed straight towards Earth? At some point in the next few months or years, this thing is going to crash into Earth or flip our poles, or push us out of our orbit, or some other horrible civilization destroying disaster. Are these rumours true? Is there a Planet X on a collision course with Earth? Unlike some of the answers science gives us, where we need to give a vague and nuanced answers, like yes AND no, or Maybe, well, it depends... I’m glad to give a straight answer: No. Any large object moving towards the inner Solar System would be one of the brightest objects in the night sky. It would mess up the orbits of the other planets and asteroids that astronomers carefully observe every night. There are millions of amateur astronomers taking high quality images of the night sky. If something was out there, they’d see it. These rumours have been popping up on the internet for more than a decade now, and I’m sure we’ll still be debunking them decades from now. What people are calling Planet X, or Nibiru, or Wormwood, or whatever doesn’t exist. But is it possible that there are large, undiscovered objects out in the furthest reaches of Solar System? Sure. Astronomers have been searching for Planet X for more than a hundred years. In the 1840s, the French mathematician Urbain Le Verrier calculated that another large planet must be perturbing the orbit of Uranus. He predicted the location where this planet would be, and then German astronomer Johann Gottfried Galle used those coordinates to discover Neptune right where Le Verrier predicted. The famed astronomer Percival Lowell died searching for the next planet in the Solar System, but he made a few calculations about where it might be found. And in 1930, Clyde William Tombaugh successfully discovered Pluto in one of the locations predicted by Lowell. Astronomers continued searching for additional large objects, but it wasn’t until 2005 that another object the size of Pluto was finally discovered by Mike Brown and his team from Caltech: Eris. Brown and his team also turned up several other large icy objects in the Kuiper Belt; many of which have been designated dwarf planets. We haven’t discovered any other large objects yet, but there might be clues that they’re out there. In 2012, the Brazilian astronomer Rodney Gomes calculated the orbits of objects in the Kuiper Belt and found irregularities in the orbits of 6 objects. This suggests that a larger object is further out, tugging at their orbits. It could be a Mars-sized object 8.5 billion km away, or a Neptune-sized object 225 billion km away. There’s another region at the edge of the Solar System called the Oort Cloud. This is the source of the long-period comets that occasionally visit the inner Solar System. It’s possible that large planets are perturbing the orbits of comets with their gravity, nudging these comets in our direction. So, feel free to ignore every single scary video and website that says an encounter with Planet X is coming. And use that time you saved from worrying, and use it to appreciate the amazing discoveries being made in space and astronomy every day.

In a classic episode of this video series, I did the calculations for how fast the Earth is spinning. We know the Earth is rotating, but why? Why is it spinning? Why is everything in the Solar System spinning? And why is it mostly all spinning in the same direction? It can’t be a coincidence. Look down on the Earth from above, and you’d see that it’s turning in a counter-clockwise direction. Same with the Sun, Mars and most of the planets. 4.54 billion years ago, our Solar System formed within a cloud of hydrogen not unlike the Orion Nebula, or the Eagle Nebula, with its awesome pillars of creation. Then, it took some kick, like from the shockwave from a nearby supernova, and this set a region of the cold gas falling inward through its mutual gravity. As it collapsed, the cloud began to spin. But why? It’s the conservation of angular momentum. Think about the individual atoms in the cloud of hydrogen. Each particle has its own momentum as it drifts through the void. As these atoms glom onto one another with gravity, they need to average out their momentum. It might be possible to average out perfectly to zero, but it’s really really unlikely. Which means, there will be some left over. Like a figure skater pulling in her arms to spin more rapidly, the collapsing proto-Solar System with its averaged out particle momentum began to spin faster and faster. This is the conservation of angular momentum at work. As the Solar System spun more rapidly, it flattened out into a disk with a bulge in the middle. We see this same structure throughout the Universe: the shape of galaxies, around rapidly spinning black holes, and we even see it in pizza restaurants. The Sun formed from the bulge at the center of this disk, and the planets formed further out. They inherited their rotation from the overall movement of the Solar System itself. Over the course of a few hundred million years, all of the material in the Solar System gathered together into planets, asteroids, moons and comets. Then the powerful radiation and solar winds from the young Sun cleared out everything that was left over. Without any unbalanced forces acting on them, the inertia of the Sun and the planets have kept them spinning for billions of years. And they’ll continue to do so until they collide with some object, billions or even trillions of years in the future. So are you still wondering, why does the Earth spin? The Earth spins because it formed in the accretion disk of a cloud of hydrogen that collapsed down from mutual gravity and needed to conserve its angular momentum. It continues to spin because of inertia. The reason it’s all the same direction is because they all formed together in the same Solar Nebula, billions of years ago.

The night sky just wouldn’t feel right without the Moon. Where did our our friendly, familiar satellite come from? Scientists and philosophers have been wondering about this for centuries. Once Copernicus gave us our current model of the Solar System, with the Earth as just another planet and the Sun at the centre of the Solar System, this gave us a new way of looking at the Moon. The first modern idea about the formation of the Moon was called the fission theory, and it came from George Darwin, the son of Charles Darwin. He reasoned the Moon must have broken away from our planet, when the Earth was still a rapidly rotating ball of molten rock. His theory lasted from the 1800s right up until the space age. Another idea is that the Earth captured the Moon after its formation. Usually, these kinds of gravitational interactions don’t go well. Models predict that either the Moon would collide with the Earth, or get flung out into a different orbit. It’s possible that the early Earth’s atmosphere was much larger and thicker, and acted like a brake, modifying the Moon’s trajectory into a stable orbit around the Earth. Or the Earth and Moon formed together in their current positions as a binary object, with Earth taking most of the mass and the Moon forming from the leftovers. The most widely accepted theory is that the Moon was formed when a Mars-sized object slammed into the Earth, billions of years ago. This collision turned the newly formed Earth into a molten ball of rock again, and ejected material into orbit. Most of the material crashed back into the Earth, but some collected together from mutual gravity to form the Moon we have today. This theory was first conceived in 1946 by Reginald Aldworth Daly from Harvard University. He challenged Darwin’s theory, calculating that just a piece of Earth breaking off couldn’t actually allow the Moon to get to its current position. He suggested an impact could do the trick though. This idea wasn’t given much thought until a 1974 paper by Dr. William K. Hartmann and Dr. Donald R. Davis was published in the Journal Icarus. They suggested that the early Solar System was still filled with leftover moon-sized objects which were colliding with the planets. The impact theory explained many of the challenges about the formation of the Moon. For example, one question was: why do the Earth and Moon have very different-sized cores. After an impact from a Mars-sized planet, the lighter outer layers of the Earth would have been ejected into orbit and coalesced into the Moon, while the denser elements collected back together into the Earth. It also helps explain how the Moon is on an inclined plane to the Earth. If the Earth and Moon formed together, they’d be perfectly lined up with the Sun. But an impactor could come from any direction and carve out a moon. One surprising idea is that the impact actually created two moons for the Earth. The second, smaller object would have been unstable and eventually slammed into the far side of the Moon, explaining why the surface on the far side of the Moon is so different from the near side. Even though we don’t know for sure how the Moon formed, the giant impact theory holds the most promise, and you can bet that scientists are continuing to look for clues to tell us more.

In a previous video, I talked about the Fermi Paradox. Our Universe is big, and it’s been around for a long time. So why don’t we see any evidence of aliens? If they are out there, why haven’t they contacted us, and how do we contact them? What methods might they use to try and contact us? Where do we look for signs of alien civilizations? The search for extraterrestrial intelligence, otherwise known as SETI, are the methods that scientists have proposed to discover evidence of aliens in the Universe. Perhaps the most famous method is listening for their signals. Here on Earth, we have exploited the radio spectrum to send signals through the air. We even use it to communicate with spacecraft in the Solar System. So, since it works so well for us, it makes sense that aliens might use radio waves to communicate from star to star. If there’s an alien civilization out there beaming a signal directly at the Sun, our largest radio telescopes should be able to pick up their signal. The problem is that the galaxy is huge, with hundreds of billions of stars. Any one of which could be the world where the aliens live. Furthermore, we don’t know which frequency the aliens might use to communicate with us. Even though the search for ET has been going for many years, we’ve only explored a fraction of the millions of available stars and frequencies on the radio spectrum. So far, no definitive signal has been discovered. Another possibility is that aliens are using lasers to communicate with us. An alien could target an incredibly powerful laser at our star, and it would be detectable with our large optical telescopes. There have been a few dedicated searches for laser communication, and scientists have proposed we could search for these alien signals at the same time we’re searching for extrasolar planets. Again, so far nothing has turned up. It’s possible that aliens use a more exotic method of communication, like neutrinos. Neutrinos are generated in high energy collisions, and can pass right through planets with ease. They would be incredibly difficult to detect with our current technology, but maybe advances in the future will make that a possible communication method. But maybe Instead of searching for signals, we could look for their artifacts. If the energy of transmitting signals across the vast reaches of space is too much, it might make more sense for aliens to construct self-replicating probes and let them journey from star to star. These probes could leave behind an obvious alien-made structure which we could discover once we become a true spacefaring species. We could also detect aliens by their impact on their home planets. With a large enough space telescope, we should be able to study the atmosphere of planets orbiting nearby stars. An industrialized civilization would probably be polluting its atmosphere with various gases -- just like we have -- which would be detectable. Finally, we could search for evidence of aliens through their structures. If a civilization starts building megastructures which block off a large portion of their star’s light, we should be able to detect evidence through our search for extrasolar planets. A gigantic space station would give off a much different light signature than a nice spherical planet as it passes in front of its star. There have been a few attempts to reach out to other worlds directly, transmitting signals out into space. It’s unlikely that these signals will actually reach any other civilization, and some scientists are concerned about the wisdom of this kind of communication. Do we really want to alert potentially hostile aliens to our location in the Milky Way? It’s exciting to think that there are other alien civilizations around us in the Milky Way, and with a little more work, we could discover their location and maybe even communicate with them. Let’s hope they’re peaceful.

For most of us, stuck here on Earth, we see very little of the rest of the Solar System. Just the bright Sun during the day, the Moon and the planets at night. But in fact, we’re embedded in a huge Solar System that extends across a vast amount of space. Which begs the question, just how big is the Solar System? Before we can give a sense of scale, let’s consider the units of measurement. Distances in space are so vast, regular meters and kilometers don’t cut it. Astronomers use a much larger measurement, called the astronomical unit. This is the average distance from the Earth to the Sun, or approximately 150 million kilometers. Mercury is only 0.39 astronomical units from the Sun, while Jupiter orbits at a distance of 5.5 astronomical units. And Pluto is way out there at 39.2 astronomical units. That’s the equivalent of 5.9 billion kilometers. If you could drive your car at highway speeds, from the Sun all the way out to Pluto, it would take you more than 6,000 years to complete the trip. But here’s the really amazing part. Our Solar System extends much, much farther than where the planets are. The furthest dwarf planet, Eris, orbits within just a fraction of the larger Solar System. The Kuiper Belt, where we find a Pluto, Eris, Makemake and Haumea, extends from 30 astronomical units all the way out to 50 AU, or 7.5 billion kilometers. And we’re just getting started. Even further out, at about 80-200 AU is the termination shock. This is the point where the Sun’s solar wind, traveling outward at 400 kilometers per second collides with the interstellar medium - the background material of the galaxy. This material piles up into a comet-like tail that can extend 230 AU from the Sun. But the true size of the Solar System is defined by the reach of its gravity; how far away an object can still be said to orbit the Sun. In the furthest reaches of the Solar System is the Oort Cloud; a theorized cloud of icy objects that could orbit the Sun to a distance of 100,000 astronomical units, or 1.87 light-years away. Although we can’t see the Oort Cloud directly, the long-period comets that drop into the inner Solar System from time to time are thought to originate from this region. The Sun’s gravity dominates local space out to a distance of about 2 light-years, or almost half the distance from the Sun to the nearest star: Proxima Centauri. Believe it or not, any object within this region would probably be orbiting the Sun, and be thought to be a part of the Solar System. Back to our car analogy for a second. At those distances, it would take you 19 million years to complete the journey to the edge of the Solar System. Even NASA’s New Horizons spacecraft, the fastest object ever launched from Earth would need 37,000 years to make the trip. So as you can see, our Solar System is a really really big place.

You might be surprised to know that I have an opinion. People often ask me for it, but tend not to give it. But I was getting into a discussion with Amy Shira Teitel from Vintage Space about the priorities of humans versus robots for space explorations and offered up this opinion. On matters of humans versus robots exploring space, this is what I think. Both, with different agendas. Opinion: Should Robots or Humans Explore Space? What's the best way to explore the Solar System? Should we send humans, or robots? Robots are durable and replaceable, while humans are creative and flexible. Space advocates line up on both sides of this discussion, and the debate can get heated. Really heated. Don't be fooled. This whole conversation is a red herring. We shouldn't have to choose between human space exploration and robotic science, and it is absolutely ridiculous that the funding for it comes into a single agency. The future of humanity will depend on us learning to live in space; to get off this planet and spread to the rest of the Solar System. The longer we remain trapped on this planet, the greater risk we face from a global catastrophe; whether it's from an asteroid strike or a global plague. We, as a species, are keeping all our eggs in one basket, I don't need to tell you how important science is. Our modern marvels are a direct result of the scientific method. The fact that you can even see this video (well, or read this article) should be all you need to know about the importance of science. And we have no idea what we'll find out there in space when we go exploring. Were it up to me, I'd separate space exploration into two agencies, with completely different agendas and budgets. On the science side, we need a fleet of robotic spacecraft and satellites continuously launching into space. We'd settle on a rugged, multi-purpose vehicle, which carries a variety of payloads and scientific instruments. The Curiosity Rover was an amazing success, and NASA should just keep building more rovers exactly like it. Give it cameras, grinders and scoops, but then keep the instruments open to the scientific community. Every two years, another identical rover will blast off to the Red Planet, hurling a fresh set of instruments to a new location. Let's send a rover and an orbiter every two years to Mars, and similar probes to other worlds, only the scientific instruments would need change. In a few years, there would be versions of the exact same spacecraft orbiting planets, asteroids and moons. Over time, our observation of the Solar System would extend outward like a nervous system, gathering scientific knowledge at a terrific rate. For human space exploration, we need to learn to live in space in increasingly complex ways: low Earth orbit, lunar orbit, on the lunar surface, on Mars, on asteroids, at Saturn, in the Lagrange points, et cetera. Remember the Gemini program back in the 1960s? Each mission was an incremental step more complicated than the previous one. On one mission, the goal was just to learn if humans could survive in space for 14 days. In another mission, the goal was just to learn how to dock two spacecraft together. This gave NASA the knowledge they needed to attempt an ambitious human landing on the Moon. Instead of flying in low-Earth orbit for decades, our human space program could continuously advance our knowledge of what it takes to survive - and eventually thrive - in space. If NASA investigates the technologies that the private sector considers too risky to invest in, it will help jump start space exploration. In this modern era of budget cuts, it breaks my heart that people are forced to choose between space science and human exploration. It shouldn't be this way. They have almost nothing in common. Let's do science, because science is important. And let's put humans in space, because humanity is important.

No answers today, only a question. But it’s one of the most interesting and meaningful questions we can possibly ask. Where does life come from? How did we get from no life on Earth, to the rich abundance we see today? Charles Darwin first published our modern theories of evolution - that all life on Earth is related; adapting and changing over time. Look at any two creatures on Earth and you can trace them back to a common ancestor. Humans and chimpanzees share a common ancestor from at least 7 million years ago. Trace back far enough, and you’re related to the first mammal who lived 220 million years ago. In fact, you and bacteria can trace a family member who lived billions of years ago. Keep going back, and you reach the oldest evidence of life on Earth, about 3.9 billion years ago. But that’s as far as evolution can take us. The Earth has been around for 4.5 billion years, and those early years were completely hostile to life. The early atmosphere was toxic, and a constant asteroid bombardment churned the landscape into a worldwide ocean of molten rock. As soon as the environment settled down to be relatively habitable, life appeared. Just half a billion years beyond the formation of the Earth. So how did life make the jump from raw chemicals to the evolutionary process we see today? The term for this mystery is abiogenesis and scientists are working on several theories to explain it. One of the first clues is amino acids, the building blocks of life. In 1953, Stanley Miller and Harold Urey demonstrated that amino acids could form naturally in the environment of the early Earth. They replicated the atmosphere and chemicals present, and then used electric sparks to simulate lightning strikes. Amazingly, they found a variety of amino acids in the resulting primordial soup. Other scientists replicated the experiment, even changing the atmospheric conditions to match other models of the early Earth. Instead of water, methane, ammonia and hydrogen, they wondered what would happen if the atmosphere contained hydrogen sulfide and sulfur dioxide from volcanic eruptions. Environments around volcanic vents at the bottom of the ocean might have been the perfect places to get life started, introducing heavier metals like iron and zinc. Perhaps ultraviolet rays from the younger, more volatile Sun, or abundant radiation from natural uranium deposits played a role in pushing life forward into an evolutionary process. What if life didn’t start on Earth at all? What if the building blocks came from space, drifting through the cosmos for millions of years. Astronomers have discovered amino acids in comets, and even alcohol floating in distant clouds of gas and dust Maybe it wasn’t the organic chemicals that came first, but the process of self organization. There are examples of inorganic chemicals and metals that can organize themselves under the right conditions. The process of metabolism came first, and then organic chemicals adopted this process. It’s even possible that life formed multiple times on Earth in different eras. Although all life as we know it is related, there could be a shadow ecosystem of microbial life forms in our soil or oceans which is completely alien to us. So how did life get here? We just don’t know. Maybe we’ll discover life on other worlds and that will give us a clue, or maybe scientists will create an experiment that finally replicates the jump from non-life to life. We may never discover the answer.

Up until 20 years ago, the only planets astronomers were aware of were within our Solar System. They assumed others were out there, but none had ever been detected. Today we know of almost a thousand planets orbiting other stars. They come in a wide variety of sizes. Some are smaller than Earth, and others are more massive than Jupiter. Some are found around solitary stars, while others are located in multiple star systems. In those systems, there can be individual or even multiple planets in orbit. In fact, recent surveys suggest there are planets orbiting every single star in the Milky Way. So, what methods do astronomers use to find these “extrasolar planets”? The first extrasolar planet was discovered in 1991. It was found orbiting a pulsar, a dead star that rotates rapidly, firing out bursts of radiation on an eerily precise interval. As the planets orbit the pulsar, they pull it back and forth with their gravity. This slightly changes the wavelength of the radiation bursts streaming from the exotic star. Astronomers were able to measure these changes, and calculate the orbits of multiple planets. Radial Velocity Method The golden age of extrasolar planet discovery began in 1995 when a team from the University of Geneva discovered a planet orbiting the nearby star 51 Pegasi. Astronomers used spectroscopy to break up the light to reveal the elements in its stellar atmosphere. They carefully measured how the wavelengths of light were Doppler shifted over time, and used a technique known as the radial velocity method. They calculated the star’s average motion, and discovered slight variations, as if something was yanking the star towards and away from us. That something, was a planet. In fact, this planet was unlike anything we have in the Solar System. 51 Pegasi B has about half the mass of Jupiter and it orbits much closer to its parent star. Closer even, than Mercury to the Sun. Until this discovery, astronomers didn’t think it was possible for planets to orbit this close, and have had to revise their theories on planetary formation. Many Hot Jupiter planets have been discovered since, some in even more extreme environments. Gravitational Microlensing Another method astronomers use to find planets is called gravitational microlensing. It works by carefully measuring the brightness of one star as it passes in front of another. The foreground star acts like a lens, focusing the light with its gravity and causing the star to brighten for a few hours. If the foreground star has planets, these will create a telltale spike in the light signature coming from the event. Amateur astronomers around the world participate in microlensing studies, imaging stars quickly when an event is announced. Transit Method The most successful way of finding planets is the transit method. This is where telescopes measure the total amount of light coming from a star, and detect a slight variation in brightness as a planet passes in front. Using this technique, NASA’s Kepler Mission has turned up thousands of candidate planets. Including some less massive than Earth, and others in the star’s habitable zone. From the Kepler data, It’s just a matter of time before the holy grail of planets is uncovered... an Earth-sized world, orbiting a Sun-like star within the habitable zone. All of these techniques are limited as they require the planets to be orbiting directly between us and their star. If the planets orbit above or below this plane, we just can’t detect them. Coronographs There is another method in the works that would unleash the discovery of extrasolar planets, coronographs. Imagine if you could block all the light from the star, and only see the planets in orbit. This technique has been used for observing the Sun’s atmosphere, but it requires much more precision to see distant stars. One idea is to position a sunflower-shaped starshade in space, 125,

There are services which will let you name a star in the sky after a loved one. You can commemorate a special day, or the life of an amazing person. But can you really name a star? The answer is yes, and no. Names of astronomical objects are agreed upon by the International Astronomical Union. If this name sounds familiar, it's the same people who voted that Pluto is not a planet. Them. There are a few stars with traditional names which have been passed down through history. Names like Betelgeuse, Sirius, or Rigel. Others were named in the last few hundred years for highly influential astronomers. These are the common names, agreed upon by the astronomical community. Most stars, especially dim ones, are only given coordinates and a designation in a catalog. There are millions and millions of stars out there with a long string of numbers and letters for a name. There's the Gliese catalog of nearby stars, or the Guide Star Catalog which contains 945 million stars. The IAU hasn't taken on any new names for stars, and probably won't ever. The bottom line is that numbers are much more useful for astronomers searching and studying stars. But what about the companies that will offer to let you name a star? Each of these companies maintains their own private database containing stars from the catalog and associated star names. They'll provide you with a nice certificate and instructions for finding it in the sky, but these names are not recognized by the international astronomical community. You won't see your name appearing in a scientific research journal. In fact, it's possible that the star you've named with one organization will be given a different name by another group. So can you really name a star after yourself or a loved one? Yes, you can, in the same way that you can name an already-named skyscraper after yourself. Everyone else might keep calling it the Empire State Building, but you'll have a certificate that says otherwise. There are a few objects that can be named, and recognized by the IAU. If you're the first person to spot a comet, you'll have it named after you, or your organization. For example, Comet Shoemaker-Levy was discovered simultaneously by Eugene Shoemaker and David Levy. If you discover asteroids and Kuiper Belt Objects, you can suggest names which may be ratified by the IAU. Asteroids, as well as comets, get their official numerical designation, and then a common name. The amateur astronomer Jeff Medkeff, who tragically died of liver cancer at age 40, named asteroids after a handful of people in the astronomy, space and skeptic community. Kuiper Belt Objects are traditionally given names from mythology. And so, Pluto Killer Mike Brown's Caltech team suggested the names for Eris, Haumea and Makemake. So what about extrasolar planets? Right now, these planets are attached to the name of the star. For example, if a planet is discovered around one of the closer stars in the Gliese catalog, it's given a letter designation. An organization called Uwingu is hoping to raise funds to help discover new extrasolar planets, and then reward those funders with naming rights, but so far, this policy hasn't been adopted by the IAU. Personally, I think that officially allowing the public to name astronomical objects would be a good idea. It would spur the imagination of the public, connecting them directly to the amazing discoveries happening in space, and it would help drive funds to underfunded research projects. And that would be a good thing. Note: You can also visit a non-profit adopt-a-star program that supports Kepler research called the Pale Blue Dot Adopt-A-Star project!

I love it when scientists discover something unusual in nature. They have no idea what it is, and then over decades of research, evidence builds, and scientists grow to understand what's going on. My favorite example? Quasars. Astronomers first knew they had a mystery on their hands in the 1960s when they turned the first radio telescopes to the sky. They detected the radio waves streaming off the Sun, the Milky Way and a few stars, but they also turned up bizarre objects they couldn't explain. These objects were small and incredibly bright. They named them quasi-stellar-objects or "quasars", and then began to argue about what might be causing them. The first was found to be moving away at more than a third the speed of light. But was it really? Maybe we were seeing the distortion of gravity from a black hole, or could it be the white hole end of a wormhole. And If it was that fast, then it was really, really far... 4 billion light years away. And it generating as much energy as an entire galaxy with a hundred billion stars. What could do this? Here's where Astronomers got creative. Maybe quasars weren't really that bright, and it was our understanding of the size and expansion of the Universe that was wrong. Or maybe we were seeing the results of a civilization, who had harnessed all stars in their galaxy into some kind of energy source. Then in the 1980s, astronomers started to agree on the active galaxy theory as the source of quasars. That, in fact, several different kinds of objects: quasars, blazars and radio galaxies were all the same thing, just seen from different angles. And that some mechanism was causing galaxies to blast out jets of radiation from their cores. But what was that mechanism? We now know that all galaxies have supermassive black holes at their centers; some billions of times the mass of the Sun. When material gets too close, it forms an accretion disk around the black hole. It heats up to millions of degrees, blasting out an enormous amount of radiation. The magnetic environment around the black hole forms twin jets of material which flow out into space for millions of light-years. This is an AGN, an active galactic nucleus. When the jets are perpendicular to our view, we see a radio galaxy. If they're at an angle, we see a quasar. And when we're staring right down the barrel of the jet, that's a blazar. It's the same object, seen from three different perspectives. Supermassive black holes aren't always feeding. If a black hole runs out of food, the jets run out of power and shut down. Right up until something else gets too close, and the whole system starts up again. The Milky Way has a supermassive black hole at its center, and it's all out of food. It doesn't have an active galactic nucleus, and so, we don't appear as a quasar to some distant galaxy. We may have in the past, and may again in the future. In 10 billion years or so, when the Milky way collides with Andromeda, our supermassive black hole may roar to life as a quasar, consuming all this new material. If you'd like more information on Quasars, check out NASA's Discussion on Quasars, and here's a link to NASA's Ask an Astrophysicist Page about Quasars. We've also recorded an entire episode of Astronomy Cast all about Quasars Listen here, Episode 98: Quasars. Sources: UT-Knoxville, NASA, Wikipedia

Did you know you can distinguish between stars and planets in the sky? Stars twinkle, planets don’t. Okay, that’s not actually correct. The stars, planets, even the Sun and Moon twinkle, all in varying amounts. Anything outside the atmosphere is going to twinkle. If you’re feeling a little silly using the word twinkle over and over again, we can also use the scientific term: astronomical scintillation. You can’t feel it, but you’re carrying the entire weight of the atmosphere on your shoulders. Every single square inch of your skin is getting pushed by 15 pounds of pressure. And even though astronomers need our atmosphere to survive, it still drives them crazy. As it makes objects in space so much harder to see. Stars twinkle, I mean scintillate, because as light passes down through a volume of air, turbulence in the Earth’s atmosphere refracts light differently from moment to moment. From our perspective, the light from a star will appear in one location, then milliseconds later, it’ll be distorted to a different spot. We see this as twinkling. So why do stars appear to twinkle, while planets don’t? Stars appear as a single point in the sky, because of the great distance between us and them. This single point can be highly affected by atmospheric turbulence. Planets, being much closer, appear as disks. We can’t resolve them as disks with our eyes, but it still averages out as a more stable light in the sky. Astronomers battle atmospheric turbulence in two ways: First, they try to get above it. The Hubble Space Telescope is powerful because it’s outside the atmosphere. The mirror is actually a quarter the size of a large ground-based observatory, but without atmospheric distortion, Hubble can resolve galaxies billions of light-years away. The longer it looks, the more light it gathers. Second, they try to compensate for it. Some of the most sophisticated telescopes on Earth use adaptive optics, which distorts the mirror of the telescope many times a second to compensate for the turbulence in the atmosphere. Astronomers project a powerful laser into the sky, creating an artificial star within their viewing area. Since they know what the artificial star should look like, they distort the telescope’s mirror with pistons cancelling out the atmospheric distortion. While it’s not as good as actually launching a telescope into space, it’s much, much cheaper. Now you know why stars twinkle, why planets don’t seem to twinkle as much, and how you can make all of them stop. We have written many articles about stars here on Universe Today. Here's an article that talks about a technique astronomers use to minimize the twinkle of the Earth's atmosphere. If you'd like more information on stars, check out Hubblesite's News Releases about Stars, and here's the stars and galaxies homepage. We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

When tiny grains of dust impact our atmosphere, they leave a trail of glowing material, like a streak of light across the sky. This is a meteor, or a shooting star. On any night, you can go outside, watch the sky, and be guaranteed to see one. Individual meteors start as meteoroids - pieces of rock smaller than a pebble flying around the Solar System. Even though they’re tiny, these objects can be moving at tens of thousands of kilometers per hour. When they hit Earth’s atmosphere, they release tremendous amounts of energy, burning up above an altitude of 50 kilometers. As they disintegrate, they leave a trail of superheated gas and rocky sparks which last for a moment in the sky, and then cool down and disappear from view. Throughout the year there are several meteor showers, when the number of meteors streaking through the sky increases dramatically. This happens when the Earth passes through the trail of dust left by a comet or asteroid. Meteor showers are when night sky puts on a special show, and it’s a time to gather your friends and family together and enjoy the spectacle. Some showers produce only a trickle of objects, while others, like the famous Perseid meteor shower, can dependably bring dozens of meteors each hour. If the trail is dense enough, we can get what is called a meteor storm. The most powerful meteor storms in history truly made it look like the sky was falling. The Leonids in 1833 produced hundreds of thousands per hour. Meteor showers take their name from the constellation from where they appear to originate. For example, the Perseids trace a trail back to the constellation Perseus; although you can see them anywhere across the sky. You can see meteors any time of the year, and you don’t need any special equipment to enjoy an average meteor shower. But here are some ways you can improve your experience. You’ll want to find a location with as clear a view to the horizon in as many directions as possible. An open field is great. Lie on your back, or on a reclining chair, look up to the sky ... and be patient. You probably won’t see a meteor right away, but after a few minutes, you should see your first one. The longer you look, the more you’ll see, and the better chance you’ll have of seeing a bolide or fireball; a very bright meteor that streaks across the sky, leaving a trail that can last for a long time. You can see meteors any time that it’s dark, but the most impressive ones happen in the early morning, when your location on Earth is ploughing directly into the space dust. You also want the darkest skies you can get, far away from city light pollution, and many hours after the Sun has gone down. Enjoy the early evening meteors, but then set your alarm and get up around 4 in the morning to see the real sky show. If I could only see one meteor shower every year, it would have to be the Perseids. These come when the Earth passes through the tail of Comet Swift-Tuttle, and peak around August 12th every year. It’s not always the most active shower, but it’s warm outside in the Northern hemisphere, and this is a fun activity to do with your friends and family. Now get outside, and enjoy a meteor shower.