Space and astronomy news
Hosts: Fraser Cain and Scott Lewis
Astronomers: David Dickinson, Gary Gonella, Roy Salisbury, Sharin Ahmed, Stuart Forman, Mike Simmons
and some gorgeous pics from Cory Schmitz in the Southern Hemisphere
Scott also shares pics from the viewers
Apps used by Scott: Phases of the Moon and Stellarium
Continue reading “Virtual Star Party – April 6, 2014: Saturn Rising”
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
Host: Nicole Gugliucci (cosmoquest.org / @noisyastronomer)
Guests: Morgan Rehnberg, Scott Lewis, Nancy Atkinson, Dave Dickinson
This Week’s Stories:
Morgan Rehnberg (cosmicchatter.org / @cosmic_chatter):
NASA lowballs Europa mission
Enceladus ocean confirmed?
Scott Lewis (@ScientificScott):
NASA cutting ties w/ Russia except ISS
Nancy Atkinson (@Nancy_A):
Skydiver Almost Hit By Meteor
Dave Dickinson (@astroguyz):
Mars Opposition
Lunar Eclipse
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
In a Universe that’s expanding apart, isn’t it strange that Andromeda is actually drifting towards us? Dr. Thad Szabo from Cerritos College explains why this is happening.
“I’m Thad Szabo, and I teach astronomy and physics at Cerritos College.”
Is Andromeda drifting towards us?
“The reason that we see Andromeda moving toward us is because it’s nearby enough, and the Milky Way is massive enough and Andromeda is massive enough that they’re gravity is strong enough that there is not enough space between them that the space was able to expand and push them apart against the force of gravity. So if you take the Milky Way, all of its stars and all of its gas and dust, all of its dark matter, you’re looking at something that’s a trillion times the mass of the sun. You have the same for Andromeda, and they’re less than a mega parsec apart – to Andromeda, its about 2.2 billion light years. And so with that distance and that much mass, that’s close enough that gravity is drawing them together. Most galaxies, because they’re so distant, you do see them moving away due to the expansion of the universe.”
“But actually M81, which is about 12 million light years away, is also moving towards the Milky Way. It’s the most distant galaxy that doesn’t show red shift. So there’s enough gravity in this local group – I guess the local group is typically the Milky Way galaxy, the Andromeda galaxy, the Triangulum galaxy, and however many tens of dwarf galaxies that we’ve either discovered or haven’t discovered yet. But there’s also a bubble of about ten to twenty major size galaxies extending out to about fifteen million light years or so, and that’s kind of right on the border between where the expansion of the universe would drive things apart and where the gravity is strong enough to hold things together.”
Spiral galaxies get their name because of their beautiful spiral shape and iconic arms. But why do galaxies have these spiral shapes, and what causes the arms?
Galaxies are some of the most beautiful and inspiring structures in the Universe. As you know, they aren’t solid disks, they’re a gigantic spill of individual stars webbed together by gravity. There are a few rough fundamental shapes that a galaxy can have, and the bulk of these are some variation of a spiral. Each one with twisting arms of stars reaching tens of thousands of light years in every direction along a plane, out from a galactic core.
So what gives them this characteristic spiral shape? Earliest galaxies didn’t have clearly defined spiral arms. They were either two-armed or, had thick irregular chaotic woolly arms with star forming clumps. After 3.6 billion years, however, the chaos had settled down into the shapes we see today. But it took until the Universe was 8 billion years old for these modern multi-armed spirals, like the Milky Way or Andromeda to appear.
So where did they come from? These arms are in fact density waves passing through the galaxy, with stars moving in and out of the waves. The arms themselves aren’t permanent structures made of the same clumps of stars.
Imagine driving down a highway and people are slowing down to gape slack-jawed a crashed alien saucer. Cars will slow down as they reach the saucer and form a clump, and then the car in the lead of the clump will accelerate and proceed down the highway as other cars progress through the clump to take their place.
This is a great analogy for movement in a galaxy. As a density wave approaches, stars accelerate towards it. Then they slow down as they move away from it. Just like a comet falling into the gravity well of the Sun. And when the density wave moves through an area, it kicks off an era of star formation. So the material of the galaxy is being constantly stirred and new stars are born as a density wave makes its way through the galaxy.
When you picture this, keep in mind that stars closer to the core of the galaxy orbit faster than the spiral arm, and the stars further out go more slowly. Our galaxy, the Milky Way takes about 240 million years to complete a full rotation. But we pass through a major spiral arm every 100 million years or so, remaining in the higher density region for about 10 million years. Astronomers have only recently figured out why these arms exist in the first place.
Originally, they suspected it might be like a garden sprinkler, with material fountaining out from the center of the galaxy, or channeled by magnetic fields. They also thought that the arms might be transient features. Appearing and disappearing over time. But new evidence and simulations show they’re long lasting, they believe the arms themselves form as a result of giant molecular clouds of hydrogen. These clouds initiate the arms and keep the shape sustained over billions of years.
What do you think? What’s your favorite spiral galaxy? Tell us in the comments below.
When the United States helped defeat Germany at the end of World War II, they acquired the German rocket scientist Wernher von Braun. He had already developed the German V2 rocket program, and went on to design all the major hardware of the US rocket program. This week, we talk about von Braun’s life and accomplishments.
Continue reading “Astronomy Cast Ep. 340: Wernher von Braun”
Pamela has a day job, remember? As an astronomer? Recently the 45th Lunar and Planetary Science Conference occurred in the The Woodlands, Texas. Pamela and guest astronomer Sondy Springmann will let us know about the big announcements made at this year’s conference.?
Continue reading “Astronomy Cast Ep. 341: 45th Lunar and Planetary Science Conference”
When you look into the night sky, you’re seeing tremendous distances away, even with your bare eyeball. But what’s the most distant object you can see with the unaided eye? And what if you get help with a pair of binoculars, a telescope, or even with the Hubble Space Telescope.
Standing at sea level, your head is at an altitude of 2 meters, and the horizon appears to be about 3 miles, or 5 km away. We’re able to see more distant objects if they’re taller, like buildings or mountains, or when we’re higher up in the air. If you get to an altitude of 20 meters, the horizon stretches out to about 11 km. But we can see objects in space which are even more distant with the naked eye. The Moon is 385,000 km away and the Sun is a whopping 150 million km. Visible all the way down here on Earth, the most distant object in the solar system we can see, without a telescope, is Saturn at 1.5 billion km away.
In the very darkest conditions, the human eye can see stars at magnitude 6.5 or greater. Which works about to about 9,000 individual stars. Sirius, the brightest star in the sky, is 8.6 light years. The most distant bright star, Deneb, is about 1500 light years away from Earth. If someone was looking back at us, right now, they could be seeing the election of the 52nd pope, St. Hormidas, in the 6th Century.
There are even a couple of really bright stars in the 8000 light year range, that we might just barely be able to see without a telescope. If a star detonates, we can see it much further away. The famous 1006 supernova was the brightest in history, recorded in China, Japan and the Middle East.
It was a total of 7,200 light years away and was visible in the daytime. There’s even large structures we can see. Outside the galaxy, the Large Magellanic Cloud is 160,000 light years and the Small Magellanic Cloud is almost 200,000 light years away. Unfortunately for us up North, these are only visible from Southern Hemisphere.The most distant thing we can see with our bare eyeballs is Andromeda at 2.6 million light years, which in dark skies looks like a fuzzy blob.
If we cheat and get a little help, say with binoculars – you can see magnitude 10 – fainter stars and galaxies at more than 10 million light-years away. With a telescope you can see much, much further. A regular 8-inch telescope would let you see the brightest quasars, more than 2 billion light years away. Using gravitational lensing the amazing Hubble space telescope can see galaxies, incredibly far out, where the light had left them just hundreds of millions of years after the Big Bang.
If you could see in other wavelengths, you could see different distances. Fortunately for our precious radiation sensitive organs, Gamma and X rays are blocked by our atmosphere. But if you could see in that spectrum, you could see objects exploding billions of light years away. And if you could see in the radio spectrum, you’d be able to see the cosmic microwave background radiation, surrounding us in all directions and marking the edge of the observable universe.
Wouldn’t that be cool? Well, maybe we can… just a little. Turn on your television, some of the static on the screen is this very background radiation, the afterglow of the Big Bang.
What do you think? If you could see far out in the Universe what would you like a close up view of? Tell us in the comments below.
Host: Fraser Cain
Astrojournalists: Morgan Rehnberg, David Dickinson
Special Guest: Dr. Alan Stern, Principle Investigator of New Horizons, Founder of Uwingu
Continue reading “Weekly Space Hangout – March 28, 2014: Uwingu & New Dwarf Planet News”
Space is a hostile environment for human beings. No part of it will permit you to survive longer than a minute. But what’s the fastest way to die in space?
Just in case you were planning to jump out into the vacuum of space without a spacesuit, I urge you to reconsider. There’s nothing but painful suffocation and death. Do not do it.
You probably wouldn’t be here if you weren’t wondering, just how lethal is space? What are all the ways space is trying to kill you? Space has a Swiss army knife of methods to do you in. You won’t be surprised to learn that classic sci-fi usually had it wrong. If you jumped out into the cold deep void without a protective suit, you wouldn’t pop like a giant pressurized juicy meat pimple. Your blood doesn’t boil, and you don’t flash freeze.
The good news is even though there is a pressure difference, human skin is strong enough to keep your body together. The bad news is you just plain old asphyxiate, almost instantaneously. The human body has about 15 seconds of usable oxygen in the blood. Once you run through that oxygen, you’ll take a quick space nap and then die a few minutes later.
On Earth, you can hold your breath for a few minutes but this gets much harder in space, as the low pressure forces the air out of your lungs. In fact, it would probably be wise to breathe every last bit of air out before you stepped out, since it’s coming out violently, one way or another.
Here’s the amazing thing. If you jumped out into space and could get back into a pressurized environment within a minute or so, you probably wouldn’t suffer any permanent damage, aside from a little bruising, some hypothermia and a really nasty sunburn. Stay out for any longer, though, and the damage will get worse. Beyond a few minutes and you’ll be done.Which is just fine, as you weren’t planning on going out into space without a spacesuit anyway.
Unfortunately, even tucked safely in your spacecraft, there are tremendous risks to being away from the comfort of Earth. You’ve got to be worried about radiation. Once a spacecraft leaves the protection of the Earth’s magnetic field, it’s exposed to the high levels constantly streaming through space. A trip from Earth to Mars and back again might increase your overall risk developing a fatal cancer by about 5%, and that’s a risk most astronauts are willing to take. But there are solar storms blasting out from the Sun that could deliver a lethal dose of radiation in just a few hours. Astronauts would need a safe, radiation-shielded location during these solar storms or they’d expire from acute radiation poisoning.
There are many, many other risks from traveling in space. Fire is one of the worst, failure of your oxygen system, access to clean water and food become an obvious problem. Even things we usually don’t think about, like mold building up in the damp environment of a spaceship becomes a problem.
Survive all these immediate hazards, just like here on Earth, and the long term hazards will get you. We have no idea if it’s even possible for the human body to exist in microgravity for longer than a few years. Your bones dissolve, your muscles waste away, and there might be other consequences.
So far, nobody is willing to run the experiment long enough to find out. And finally, the fastest way space can kill you is likely impact with debris. Even though space is mostly empty, there’s all kinds of material whizzing around. Every spacecraft is pockmarked with micrometeorite impacts. There are holes punched through the International Space Station’s solar panels. These tiny pieces of rock can be traveling at 10 kilometers per second when they impact the spacecraft.
Spacecraft have layers of protection to absorb smaller particles, but there’s no way to prevent larger objects from causing catastrophic damage. If those layers weren’t there you’d be a short hop skip and a jump from becoming a heavily perforated spongebob spacepants. The solution? You just have to hope they never hit.
There certainly a many ways to quickly die in space, but what’s really amazing to me is how we can actually overcome many of these risks, certainly long enough to reach other worlds in the Solar System. Traveling in space is dangerous and difficult, but the exciting thing is it’s still possible. And one day, we’ll do it.
So, even knowing the risks, would you travel in space?
Emily Lakdawalla from the planetary society describes one of the mysteries that’s currently fascinating her. There are strange structures on Mercury which have been called “hollows”. What might they be?
Continue reading “What Are These Hollows on Mercury?”