Space and astronomy news
Jocelyn Bell Burnell is an Irish astronomer, best known for being part of the team that discovered pulsars, and the following controversy when she was excluded from the Nobel Prize winning team.
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NASA’s New Horizons spacecraft just woke up from its long nap, and now it’s on final approach towards its next destination: Pluto. Over the next few months, Pluto will be getting bigger and bigger in the front window; we’ll finally get our first close-up look at this mysterious icy world on July 14, 2015.
In order to celebrate this momentous occasion, the New Horizons science team will be doing a live Google+ Hangout with Universe Today on Wednesday, December 10th at 1 pm PST / 4 pm EST.
Universe Today publisher Fraser Cain will moderate a discussion with New Horizons Principal Investigator Alan Stern, and other members of the science team: Jason Cook, Alex Parker, Simon Porter, Kelsi Singer, and Amanda Zangari.
We’ll be talking about the status of New Horizons, the science objectives of the mission, and answering questions from viewers.
Want to watch?
Click here to go to the Hangout page on Google+. Click “Yes” on the Event page and you’ll get a reminder in your calendar when we’re about to begin.
Recent Universe Today articles on New Horizon:
Pluto Spacecraft Wakes Up For An Exciting Close Encounter Next Year
Pluto’s Closeup Will Be Awesome Based On Jupiter Pics From New Horizons Spacecraft
New Horizons Sights Tiny Pluto Moon As Spacecraft Races Toward Dwarf Planet
This star is X light-years away, that galaxy is X million light-years away. That beginning the Universe is X billion light-years away. But how do astronomers know?
I’m perpetually in a state where I’m talking about objects which are unimaginably far away. It’s pretty much impossible to imagine how huge some our Universe is. Our brains can comprehend the distances around us, sort of, especially when we’ve got a pile of tools to help. We can measure our height with a tape measure, or the distance along the ground using an odometer. We can get a feel for how far away 100 kilometers is because we can drive it in a pretty short period of time.
But space is really big, and for most of us, our brains can’t comprehend the full awesomeness of the cosmos, let alone measure it. So how do astronomers figure out how far away everything is? How do they know how far away planets, stars, galaxies, and even the edge of the observable Universe is? Assuming it’s all trickery? You’re bang on.
Astronomers have a bag of remarkably clever tricks and techniques to measure distance in the Universe. For them, different distances require a different methodologies. Up close, they use trigonometry, using differences in angles to puzzle out distances. They also use a variety of standard candles, those are bright objects that generate a consistent amount of light, so you can tell how far away they are. At the furthest distances, astronomers use expansion of space itself to detect distances.
Fortunately, each of these methods overlap. So you can use trigonometry to test out the closest standard candles. And you can use the most distant standard candles to verify the biggest tools. Around our Solar System, and in our neighborhood of the galaxy, astronomers use trigonometry to discover the distance to objects.
They measure the location of a star in the sky at one point of the year, and then measure again 6 months later when the Earth is on the opposite side of the Solar System. The star will have moved a tiny amount in the sky, known as parallax. Because we know the distance from one side of the Earth’s orbit to the other, we can calculate the angles, and compute the distance to the star.
I’m sure you can spot the flaw, this method falls apart when the distance is so great that the star doesn’t appear to move at all. Fortunately, astronomers shift to a different method, observing a standard candle known as a Cepheid variable. These Cepheids are special stars that dim and brighten in a known pattern. If you can measure how quickly a Cepheid pulses, you can calculate its true luminosity, and therefore its distance.
Cepheids let you measure distances to nearby galaxies. Out beyond a few dozen megaparsecs, you need another tool: supernovae. In a very special type of binary star system, one star dies and becomes a white dwarf, while the other star lives on. The white dwarf begins to feed material off the partner star until it hits exactly 1.4 times the mass of the Sun. At this point, it detonates as a Type 1A supernova, generating an explosion that can be seen halfway across the Universe. Because these stars always explode with exactly the same amount of material, we can detect how far away they are, and therefore their absolute brightness.
At the greatest scales, astronomers use the Hubble Constant. This is the discovery by Edwin Hubble that the Universe is expanding in all directions. The further you look, the faster galaxies are speeding away from us. By measuring the redshift of light from a galaxy, you can tell how fast it’s moving away from us, and thus its approximate distance. At the very end of this scale is the Cosmic Microwave Background Radiation, the edge of the observable Universe, and the limit of how far we can see.
Astronomers are always looking for new types of standard candles, and have discovered all kinds of clever ways to measure distance. They measure the clustering of galaxies, beams of microwave radiation from stars, and the surface of red giant stars – all in the hopes of verifying the cosmic distance ladder. Measuring distance has been one of the toughest problems for astronomers to crack and their solutions have been absolutely ingenious. Thanks to them, we can have a sense of scale for the cosmos around us.
What concept in astronomy do you have the hardest time holding in your brain? 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)
Continue reading “Weekly Space Hangout – Dec. 5, 2014: Orion’s Successful Launch!”
We’ve talked about the biggest stars, but what about the smallest stars? What’s the smallest star you can see with your own eyes, and how small can they get?
Space and astronomy is always flaunting its size issues. Biggest star, hugest nebula, prettiest most talented massive galaxy, most infinite universe, and which comet came out on top in the bikini category. Blah blah blah.
In an effort to balance the scales a little we’re going look at the other end of the spectrum. Today we’re talking small stars. First, I’m going to get the Gary Coleman and Emmanuel Lewis joke out of the way, so we can start talking about adorable little teeny tiny fusion factories.
We get big stars when we’ve got many times the mass of the Sun’s worth of hydrogen in one spot. Unsurprisingly, to get smaller stars we’ll need less hydrogen, but there’s a line we can’t cross where there’s so little, that it won’t generate the temperature and pressure at its core to ignite solar fusion. Then it’s a blob, it’s a mess. It’s clean-up in aisle Andromeda. It’s who didn’t put the lid back on the jar marked H.
So how small can stars get? And what’s the smallest star we know about? In the traditional sense, a star is an object that has enough mass and pressure in its core that it can ignite fusion, crushing atoms of hydrogen into helium.
Fusion is exothermic, releasing energy. It’s this energy that counteracts the force of gravity pulling everything inward. That gives you the size of the star and keeps it from collapsing in on itself.
By some random coincidence and fluke of nature our Sun is exactly 1 solar mass. Actually, that’s not true at all, our shame is that we use our Sun as the measuring stick for other stars. This might be the root of this size business. We’re in an endless star measuring contest, with whose is the most massive and whose has the largest circumference?
So, as it turns out, you can still have fusion reactions within a star if you get all the way down to 7.5% of a solar mass. This is the version you know as a red dwarf. We haven’t had a chance to measure many red dwarf stars, but the nearest star, Proxima Centauri, has about 12.3% the mass of the Sun and measures only 200,000 kilometers across. In other words, the smallest possible red dwarf would only be about 50% larger than Jupiter.
There is an important distinction, this red dwarf star would have about EIGHTY times the mass of Jupiter. I know that sounds crazy, but when you pile on more hydrogen, it doesn’t make the star that much bigger. It only makes it denser as the gravity pulls the star together more and more.
At the time I’m recording this video, this is smallest known star at 9% the mass of the Sun, just a smidge over the smallest theoretical size.
Proxima Centauri is about 12% of a solar mass, and the closest star to Earth, after the Sun. But it’s much too dim to be seen without a telescope. In fact, no red dwarfs are visible with the unaided eye. The smallest star you can see is 61 Cygni, a binary pair with one star getting only 66% the size of the Sun. It’s only 11.4 light years away, and you can just barely see it in dark skies. After that it’s Spock’s home, Epsilon Eridani, with 74% the size of the Sun, then Alpha Centauri B with 87%, and then the Sun. So, here’s your new nerd party fact. The Sun is the 4th smallest star you can see with your own eyes. All the other stars you can see are much bigger than the Sun. They’re all gigantic terrifying monsters.
And in the end, our Sun is absolutely huge compared to the smallest stars out there. We here like to think of our Sun as perfectly adequate for our needs, it’s ours and all life on Earth is there because of it. It’s exactly the right size for us. So don’t you worry for one second about all those other big stars out there.
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!
Margaret Geller is best known for her work on the large scale structure of the Universe, helping us understand the large clusters, super clusters and cosmic filaments that matter clumps into.
Continue reading “Astronomy Cast Ep. 359: Modern Women: Margaret Geller”
What fate awaits Phobos, one of the moons of Mars?
“All these worlds are yours except Europa, attempt no landing there.”
As much as I love Arthur C. Clarke and his books, I’ve got to disagree with his judgement on which moons we should be avoiding. Europa is awesome. It’s probably got a vast liquid ocean underneath its icy surface. There might even be life swimming down there, ready to be discovered. Giant freaky Europa whales or some kind of alien sharknado. Oh man, I just had the BEST idea for a movie.
So yea, Europa’s fine. The place we should really be avoiding is the Martian Moon Phobos. Why? What’s wrong with Phobos? Have I become some kind of Phobo…phobe? Is there any good reason to avoid this place?
Well first, its name tells us all we need to know. Phobos is named for the Greek god of Horror, and I don’t mean like the usual gods of horror as in Clive Barker, John Carpenter or Wes Craven, I mean that Phobos is the actual personification of Fear… possibly with a freaky lion’s head. And… there’s also the fact that Phobos is doomed.
Literally doomed. Living on borrowed time. Its days are numbered. It’s been poisoned and there’s no antidote. It’s got metal shards in its heart and the battery on it’s electro-magnet is starting to brown out. More specifically, in a few million years, the asteroid-like rock is going to get torn apart by the Martian gravity and then get smashed onto the planet.
It all comes down to tidal forces. Our Moon takes about 27 days to complete an orbit, and our planet takes around 24 hours to complete one rotation on its axis. Our Moon is pulling unevenly on the Earth and slowing its rotation down.
To compensate, the Moon is slowly drifting away from us. We did a whole episode about this which we’ll link at the end of the episode. On Mars, Phobos only takes 8 hours to complete an orbit around the planet. While the planet takes almost 25 hours to complete one rotation on its axis. So Phobos travels three times around the planet for every Martian day. And this is a problem.
It’s actually speeding up Mars’ rotation. And in exchange, it’s getting closer and closer to Mars with every orbit. The current deadpool gives the best odds on Phobos taking 30 to 50 million years to finally crash into the planet. The orbit will get lower and lower until it reaches a level known as the Roche Limit. This is the point where the tidal forces between the near and far sides of the moon are so different that it gets torn apart. Then Mars will have a bunch of teeny moons from the former Phobos.
And then good news! Those adorable moonlets will get further pulverized until Mars has a ring. But then bad news… that ring will crash onto the planet in a cascade of destruction to be described as “the least fun balloon drop of all time”. So, you probably wouldn’t want to live on Mars then either.
Count yourself lucky. What were the chances that we would exist in the Solar System at a time that Phobos was a thing, and not a string of impacts on the surface of Mars.
Enjoy Phobos while you can, but remember that real estate there is temporary. Might I suggest somewhere in the alien sharknado infested waters of Europa instead?
What do you think. Did Arthur C Clarke have it wrong? Should we explore Europa?
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)
Brian Koberlein (@briankoberlein)
Ramin Skibba (@raminskibba)
Dave Dickinson (@astroguyz / www.astroguyz.com)
Continue reading “Weekly Space Hangout – Nov. 21, 2014: New Images of Europa”
A star can burn its hydrogen for millions or even billions of years. But when the party’s over, black holes form in an instant. How long does it all take to happen.
Uh-oh! You’re right next to a black hole that’s starting to form.
In the J.J. Abrams Star Trek Universe, this ended up being a huge inconvenience for Spock as he tried to evade a ticked off lumpy forehead Romulan who’d made plenty of questionable life choices, drunk on Romulan ale and living above a tattoo parlor.
So, if you were piloting Spock’s ship towards the singularity, do you have any hope of escaping before it gets to full power? Think quickly now. This not only has implications for science, but most importantly, for the entire Star Trek reboot! Or you know, we can just create a brand new timeline. Everybody’s doing it. Retcon, ftw.
Most black holes come to be after a huge star explodes into a supernova. Usually, the force of gravity in a huge star is balanced by its radiation – the engine inside that sends out energy into space. But when the star runs out of fuel to burn, gravity quickly takes over and the star collapses. But how quickly? Ready your warp engines and hope for the best.
Here’s the bad news – there’s not much hope for Spock or his ship. A star’s collapse happens in an instant, and the star’s volume gets smaller and smaller. Your escape velocity – the energy you need to escape the star – will quickly exceed the speed of light.
You could argue there’s a moment in time where you could escape. This isn’t quite the spot to argue about Vulcan physiology, but I assume their reaction time is close to humans. It would happen faster than you could react, and you’d be boned.
But look at the bright side – maybe you’d get to discover a whole new universe. Unless of course Black holes just kill you, and aren’t sweet magical portals for you and your space dragon which you can name Spock, in honor of your Vulcan friend who couldn’t outrun a black hole.
Here we’ve been talking about what happens if a black hole suddenly appears beside you. The good news is, supernovae can be predicted. Not very precisely, but astronomers can say which stars are nearing the end of their lives.
Here’s an example. In the constellation Orion, Betelgeuse the bright star on the right shoulder, is expected to go supernova sometime in the next few hundred thousand years.
That’s plenty of time to get out of the way.
So: black holes are dangerous for your health, but at least there’s lots of time to move out of the way if one looks threatening. Just don’t go exploring too close!
If you were to fall through a black hole, what do you think would happen? Naw, just kidding, we all know you’d die. Why don’t you tell us what your favorite black hole sci fi story is 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!
Our focus on female astronomers continues with Sandra Faber, and Professor of Astronomy at UC Santa Cruz. Faber was part of the team that turned up the Great Attractor, a mysterious mass hidden by the disk of the Milky Way.
Continue reading “Astronomy Cast Ep. 358: Modern Women: Sandra Faber”