Space and astronomy news
Yes, we actually landed on the Moon. No, aliens didn’t crash land at Roswell. What is it about space exploration that leads to so many conspiracy theories? We’ll try to get to the bottom of these conspiracy theories, poke holes in their ridiculous ideas and help you build your baloney detection kit.
Continue reading “Astronomy Cast Ep. 339: Space Conspiracy Theories”
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.
Host: Fraser Cain
Guests: Matthew Francis, Nicole Gugliucci, Brian Koberlein, Morgan Rehnberg, Mike Simmons
Continue reading “Weekly Space Hangout – March 21, 2014: Cosmos & Gravitational Waves!”
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.
It’s safe to say that the Polish astronomer Nicolaus Copernicus shook up the whole Universe. Well, our understanding of our place in the Universe. It was Copernicus who came up with the heliocentric model, placing the Sun at the center of the Solar System, with the Earth as just another planet.
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!
Host: Fraser Cain & Scott Lewis
Astronomers: David Dickinson, Gary Gonella, Mark Behrendt, Roy Salisbury, Stuart Forman
Continue reading “Virtual Star Party – March 16, 2014”
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.”