Space and astronomy news
Host: Fraser Cain (@fcain)
Guests:
Morgan Rehnberg (cosmicchatter.org / @cosmic_chatter)
Brian Koberlein (@briankoberlein)
Alessondra Springmann (@sondy)
Ramin Skibba (@raminskibba)
Continue reading “Weekly Space Hangout – Nov. 14, 2014: Holy Rosetta! We Landed on a Comet!”
We’ve all heard that the Universe is expanding, but why is it expanding? What’s the force pushing everything outwards?
If still you don’t know that we live in an expanding Universe, then I’m clearly not doing my job.
And so once more, with feeling… the Universe is expanding. But that certainly doesn’t answer all the questions that go along with the it.
Like what’s the Universe expanding into? Which we did in another video, which I’ll list at the end of this episode. You might also want to know why is the Universe expanding? What’s making this happen? Did it give up its gym membership? Did it sign up for the gallon of ice cream of the month club? Has it completely embraced the blerch?
Edwin Hubble, the astronomer made famous by being named after a space telescope, provided the definitive evidence that the Universe was expanding. Observing distant galaxies, he observed they were fleeing outwards, in fact he was able to come up with calculations to show just how fast they were moving away from us.
Or to be more precise, he was able to show how fast all the galaxies are moving away from each other. Which was your question! Just like a minute ago! See you’re just as smart as Hubble!
So up until about 15 years ago, the only answer was momentum. The idea was that the Universe received all the energy it needed for its expansion in the first few moments after the Big Bang.
Imagine the beginning of the Universe, BOOM, like an explosion from a gun. And all the rest of the expansion is the Universe coasting outwards. For the longest time, astronomers were trying to figure out what this momentum would mean for the future of the Universe.
Would the mutual gravity of all the objects in the Universe cause it to slow to a halt at some point in the distant future, or maybe even collapse in on itself, leading to a Big Crunch? Or just clump up in piles and stay on the couch all summer because it’s maybe a little lazy and isn’t ready to start going back to the gym yet?
In 1999, astronomers discovered something completely unexpected… dark energy. As they were doing their observations to figure out exactly how the Universe would coast to a stop, they discovered that it’s actually speeding up. It’s as if that bullet is actually a rocket and it’s accelerating.
Now it appears that the Universe will not only expand forever, but the speed of its expansion will continue to accelerate faster and faster. So what’s causing this expansion? Currently, we believe it’s mostly momentum left over from the Big Bang, and the force of dark energy will be accelerating this expansion. Forever.
How do you feel about a rapidly accelerating expanding Universe? Tell us in the comments below.
And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!
It’s time for another series. This time we’ll be talking about famous female astronomers. Starting with: Vera Rubin, who first identified the fact that galaxies rotate too quickly to hold themselves together, anticipating the discovery of dark matter.
Continue reading “Astronomy Cast Ep. 357: Modern Women: Vera Rubin”
Host: Fraser Cain (@fcain)
Guests:
Morgan Rehnberg (cosmicchatter.org / @cosmic_chatter)
Brian Koberlein (@briankoberlein)
Nicole Gugliucci (cosmoquest.org / @noisyastronomer)
Continue reading “Weekly Space Hangout – Nov. 7, 2014: Ship Updates & Solar System Formation”
Shortly after the Big Bang, the Universe had cooled to the point that the first stars could form out of the primordial hydrogen. How long did it take, and what did these first stars like?
Hydrogen soup. Doesn’t that sound delicious? Perhaps not for humans, but certainly for the first stars!
Early in the Universe, in a spectacular show of stellar soupification, clouds of hydrogen atoms gathered together. They combined with one another. The collected mass got bigger and bigger, and after a time, ignition. The first stars were alive!
Well, alive in the sense that they were burning – not that they had feelings or knew what was going on, or had opinions, or were beginning to write would what would eventually become the first Onion article or anything.
But where did all that gas come from, and can we spot the evidence of those long-ago stars today? As you know, the Big Bang got our Universe off to a speedy start of expansion. It then took 400,000 years for us to see any light at all. Protons and electrons and other small particles were floating around, but it was far too hot for them to interact.
Once the power of the Big Bang finally faded, those protons and electrons paired up and created hydrogen. This is called, rather uninventively, “recombination”. I’d rather just call it hydrogen soup. We’ve got energy. But what is the secret ingredient that sparked these stars? It was just that soup clumping together over time.
We can’t say to the minute when the first stars formed, but we have a pretty good idea. The Wilkinson Microwave Anisotropy Probe, aka WMAP examined what happened when these clouds of hydrogen molecules got together, creating tiny temperature differences of only a millionth of a degree.
Over time, gravity began to yank matter from spots of lower density into the higher-density regions, making the clumps even bigger. Fantastically bigger. So big that about 200 million years after the clumps were formed, it was possible for these hydrogen molecules to ram into each other at very high speeds.
This process is called nuclear fusion. On Earth, it’s a way to produce energy. Same goes for a star. With enough nuclear reactions happening, the cloud of gas compresses and creates a glow. And these stars weren’t tiny – they were monsters! NASA says the first stars were 30 to 300 times as massive as the sun, shining millions of times brighter.
But this flashy behavior came at a price, because in only a few million years, the stars grew unstable and exploded into supernovae. These stars weren’t only exploding. They were also altering the soup around them. They were big emitters of ultraviolet light. It’s a very energetic wavelength, best known for causing skin cancer.
So, this UV light struck the hydrogen surrounding the stars. This split the atoms apart into electrons and protons again, leaving quite the mess in space. But it’s through this process that we can learn more about these earliest stars.The stars are long gone, but like a criminal fleeing the scene, they left a pile of evidence behind for their existence. Splitting these atoms was their evidence. This re-ionization is one key piece of understanding how these stars came to be.
So it was an action-packed time for the universe, with the Big Bang, then the emergence of soup and then the first stars. It’s quite an exciting start for our galactic history.
What do you think the first stars looked like?
And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!
We’re just a few days away from the official release of Paramount’s new Interstellar movie, directed by Christopher Nolan and starring Matthew McConaughey, Anne Hathaway, and Jessica Chastain.
To celebrate the movie, the cast and crew of Interstellar will be doing a special Google+ Hangout on Air at the Smithsonian’s National Air and Space Museum. They’ll broadcast for about an hour, talk about what it took to make the movie, and answer your questions… LIVE.
Wednesday, November 5th at 2:30 PM PST
And for Universe Today fans, I’m pleased to announce that I’m going to be involved in the broadcast. I’ll be participating in the Hangout, and passing along your questions to the creators.
So, if you want to participate live, and maybe even get your questions answered by the cast and crew of Interstellar, here’s what you have to do:
See you on Wednesday!
An object at rest stays at rest, and object in motion tends to stay in motion. This is inertia, defined famously by Isaac Newton in his First Law of Motion.
Continue reading “Astronomy Cast Ep. 356: Rotational Inertia”
Rockets are the perfect way to get around in space. But how do they work?
Space travel and rockets, it’s like ice cream and apple pie, or ice cream and apple pie and my face. They just go together. They belong together.
But what if I’m allergic to rockets, or have some kind of cylindrical intolerance, or flaming column sensitivity that makes me hive out? Why can’t I fly to space in balloons or airplanes or helicopters? Why do we need these pointy cubist eggplant flame tubes?
The space age followed the development of powerful V2 rockets in WW II. They could hit targets 320 km away and reach an altitude of 200 km. They were a new kind of war machine, a terrifying weapon that could hurl payloads of destruction from the skies. But this terrifying development is what brought us our modern rockets as their propulsion system can work up where there’s no air, in the vacuum of space.
How do they actually work? It all comes down to that “every action, equal and opposite reaction” thing that Newton was always going on about.
If you take a balloon, fill it with air, and then let it go. All that air rushing out propels the balloon around. This kind of balloon rocket would work perfectly well in space too although it might be a little too fragile and unpredictable to want to strap yourself to.
If we take that idea and scale it up, add some fuel tanks and fins, attitude control and optionally: astronauts. We’ve got ourselves a rocket. It works by pushing “stuff” out one end of a tube at the highest possible velocity. The faster you can blow stuff out the end, the faster the tube itself is going to go.
This means rocket science is really all about how to get the exhaust gases hurling out the backside of the rocket as quickly and forcefully as possible. The fuel can be solid, like the space shuttle’s solid rocket boosters. Or the fuel can be liquid, like the shuttle’s main fuel tank filled with liquid oxygen and hydrogen.
This fuel is ignited and completely converted into exhaust gases which blast out of the rocket’s nozzles at high velocity. Really, really high velocity.
The scary part for passengers is that modern rockets are mostly made of fuel. In fact, the weight of the space shuttle’s fuel was 20 times more than the weight of the shuttle itself. Which I believe really puts a fine point on the bravery of any astronaut. Think of a rocket as a beer can, filled with explosives, that you strap yourself to the outside of. To make a rocket go faster and shorten the travel time, you want to kick material out at a higher velocity.
NASA has experimented with ion drives for some of its missions. These highly efficient engines use electric fields to accelerate particles of xenon at much higher velocities. Even though they use a fraction of the amount of fuel, ion engines can reach much higher speeds because of the high exhaust velocity.
And even higher velocity rockets have been tabled, such as the VASIMIR engine and even antimatter engines. So how do rockets work? Just like deflating balloons, only bigger. Much much bigger. And full of explosives and modeled on a horrible and terrifying weapon from the second world war. Really, not much like a balloon at all…
Have you ever made a rocket? What’s your favorite rocketry experiment. Tell us in the comments below.
And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!
Host: Fraser Cain (@fcain)
Guests:
Morgan Rehnberg (cosmicchatter.org / @cosmic_chatter)
Ramin Skibba (@raminskibba)
Alessondra Springmann (@sondy)
Ken Kremer (kenkremer.com / @ken_kremer)
Continue reading “Weekly Space Hangout – Oct. 31, 2014: Bad Week in Space”
The Big Dipper is big. Come on, it’s right there in the name. But how big is the Big Dipper if you could see it from all angles?
Ask someone to name a constellation and they’ll usually say the Big Dipper. Anyone living in the Northern hemisphere who can draw a spoon generally can recognize it in the sky.
I am about to shake the foundations of your reality with a level of pedantry that at bare minimum should earn me a solid shaking and possibly even a face punch or two. The Big Dipper is not, and never will be a constellation.
It’s an asterism, a familiar pattern of stars in the sky. There are 88 constellations, and the Big Dipper isn’t one of them. It’s a part of the constellation of Ursa Major. In fact, the handle of your familiar spoon is actually the tail of the great bear.
Now that I’ve lulled you to sleep with some painfully uninteresting specifics, which you can bust out to make yourself unpopular at your AV Club pop and chip parties whenever someone refers to the “Big D” as a constellation. I strongly suggest whatever it is you tell them, you start off with *ACTUALLY….*
And now that you’ve made it this far, I shall reward you with what you’re seeking. Just how big is that Big Dipper? There are a couple of ways to skin this bear’s tail. We can say its size relative to the amount of sky real estate it occupies, or we can do the end to end Kessel run.
You might be surprised to know how much of the sky it takes up. Astronomers measure the sky in degrees. 360 degrees takes you all the way around the sky, and our Moon measures half a degree across.
Dubhe and Merak are the pointer stars in the Big Dipper. You could put 11 full Moons side to side in the gap between them. And about 40 full Moons from bottom corner of the Dipper to the end of its handle. So, the Big Dipper measures about 20 degrees.
Here are some easy ways to measure sizes. Your pinkie nail, held at arm’s length is half a degree. 3 fingers is 5 degrees, your fist is 10 degrees. Rocking out with devil horns are 15 degrees and hang loose or the inspector gadget phone is 25 degrees.
Trekkers and Trekkies may prefer to use the Vulcan live long and prosper measurement, which is about the same number of degrees you are from getting a romantic companion.
So, stem to stern, how big is our giant celestial ladle? I know you know those things aren’t in anything resembling a straight line. Some of the stars are closer, and some of the stars are further out. If you could make a box that completely surrounded them, how big would it be?
The closest star in the asterism is Megrez at 58 light years. and the most distant is Dubhe at 124 light-years. And yet, they all look roughly the same brightness. This means that Dubhe is a much brighter star than Megrez, and it’s just further away. Because these stars are moving in the sky what we see as a Big Dipper today didn’t always look this way. 150,000 years ago, the Big Dipper looked like this (above).
And in 150,000 years from now it’ll look like this (left). Less dipper, more plow-like. Or maybe a shoe form? Shoes are kind of like ladles, right? Super gross, terribly unhygenic ladles.
Our brains keep from exploding by being pattern making machines. We see collections of stars in the sky and turn them into shapes. But it’s all just a matter of perspective. You’ve got to be right here and now to see the sky we do. Unless you’re looking for a giant “W” in which case you’ll always find one of those. It may not be the constellation Cassiopeia, but it’ll still be a pattern in the stars.
What’s your favorite asterism? Tell us in the comments below.