The scale of things

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The Southern Skies, Lit Like Neon
Bad Astronomy at Slate dot dom | 13NOV12

One of the things I love to do on the blog is post incredibly lush and beautiful photos of the night sky, then explain them. It’s eye-candy and brain-candy. Except nourishing. OK, the candy analogy doesn’t work so well, but still, check out this incredible shot of the southern sky taken by my friend Babak Tafreshi:


^ The southern stars of Carina and Crux hang over the Very Large Telescope.
Image credit: ESO/Babak Tafreshi

What grabs your attention right away is the stunning starscape. This picture was taken in Chile, at a latitude of 24 degrees south. Many of the stars seen here never rise for those of us who live in the Northern Hemisphere; the Earth is forever in the way. We’re looking in a direction toward the Milky Way, so we see lots of stars scattered about—it’s like looking toward the downtown of a city from a suburb.

Most of the stars you see here are part of the constellation Carina, representing the keel of a ship. The brightest star in the picture, though, the blue one on the right, is called Acrux, one of the stars in Crux, the famous Southern Cross. Crux is a kite-shaped figure, with Acrux at the top and the other three to the lower left.

Dominating the shot is the ruddy glow of the mighty Carina Nebula, a vast, sprawling complex of gas and dust so large, so massive, that it’s hard to describe, let alone grasp.


Hubble picture of the massive
star Eta Carinae. Image credit:
Nathan Smith (University of
California, Berkeley)/NASAIn this nebula are thousands upon thousands of stars, born from the chaos of swirling gas. Some of the most massive stars known call this nebula home, including Eta Carinae, a star with something like 100 times the mass of our Sun—that’s near the theoretical upper limit of how massive a star can be. The more massive a star, the hotter and more energetic it is, and if Eta Car (as we in the know call it) were any bigger, it would tear itself apart. In 1843 it underwent a violent paroxysm that blasted out two lobes of material at incredible velocity, each with about as much mass as the Sun! Even from its distance of 7,500 light years, it briefly became one of the brightest stars in the sky.

The red color you see in the big picture is real: it’s from hydrogen, octillions of tons of it, set aglow by the ultraviolet light of those massive stars. They flood the gas with radiation, exciting the electrons in its atoms, making it glow in the same way a neon sign does. You can pick out smaller clumps of red hydrogen clouds as well, each lit in the same way by stars embedded inside them. Those stars have short lifetimes, living only a few million years at most. When they run out of fuel they’ll die, exploding as supernovae.

Then you’ll really see those clouds glow. And blasted apart.

Only after you gawk at the celestial treasures in this picture will you notice the far more terrestrial foreground—a trio of telescopes silhouetted against the sky. These are three of the four auxiliary telescopes for the gigantic (and prosaically named) Very Large Telescope. Each of these monsters sports a mirror more than 8 meters (25 feet) across! Not only that, using very a sophisticated technique called interferometry, the four can be combined, acting as a single, even larger telescope, capable of resolving small details in cosmic objects better even than Hubble can. It’s an extremely powerful tool used by astronomers around the world.

Babak Tefreshi, who took this shot, is an accomplished astrophotographer. He works with The World At Night, a wonderful group trying to raise awareness of the beauty of the night sky. Although I’ve been writing about Babak’s work for years, I had the pleasure of meeting him in real life for the first time just a few days ago at the Arizona Astronomy and Science Expo. It was an honor to shake the hand of a man who has brought so much beauty literally down to Earth.

I love pictures like this. They combine the heavens and the Earth, and do it with the nice twist of showing us the very machines we’ve built to help us understand the Universe we see in the picture. We’re a part of all this, which means in a very real way, as Carl Sagan said, we are a way for the cosmos to know itself.

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Why I’m loving astronomy: it’s the distance thing!
Highlights mine. Links in the original.

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Is This the Most Distant Object Ever Seen? | Phil Plait
Bad Astronomy at Slate dot com | 16NOV12

Well, this is pretty cool: A weird proto-galaxy spotted by the Hubble Space Telescope may have broken the record for the most distant object ever seen. And—if it pans out—it didn’t just break the record, it smashed it.

Here’s the picture:

^ Hubble and Spitzer Space Telescopes image of MACS0647-JD.
Image credit: NASA, ESA, M. Postman and D. Coe (STScI), and the CLASH Team

The object in question—called MACS0647-JD—is the red blob in the inset. If the calculations hold out, that gloppy looking thing may be at the mind-crushing distance of almost 13.3 billion light years. The light we see from it started on its way when the universe itself was only 420 million years old.

Just typing that made the hair on the back of my neck stand up.

So how does this work? What is this thing, and how did the scientists figure out how far away it is? OK, you’ll have to bear with me. This takes a moment to explain, and it’s a bit of a mind flip, but it’s really cool.

It’s Just a Shift to the Red

You’ve probably heard that the universe is expanding. When astronomers say that, what they mean is that space itself is expanding, carrying everything with it. I know that’s a bit of a brain-twisty thing to think about, but go with it. We have a huge amount of evidence to support this idea, and essentially no professional astronomer seriously doubts it.

What this cosmic expansion means is that galaxies that are far away are moving away from us, and the farther away they are, the faster they’re moving. You’ve probably also experienced the Doppler shift: Sounds change pitch if the source of the sound is moving toward or away from you. When a motorcycle passes you, it makes that familiar “EEEEeeeeeeeooooooowwwwwwww!” sound. The pitch—the frequency of the sound—is higher as it approaches you, then drops when it passes.

A similar thing happens with light. An object moving toward you and emitting light will have the frequency of that light increase. When it moves away from you, the frequency drops. Frequency is related to color; the blue end of the spectrum has a higher frequency than the red end. So we say the light of something moving toward you is blue shifted, and red shifted if it moves away.

When we observe distant galaxies, we see this effect! The farther away a galaxy is, the more redshifted we see its light. In fact, that’s how the universe’s expansion was first discovered. By measuring the amount of redshift we can tell how fast the galaxy is moving away from us and from that determine its distance.

It’s not that easy, but that’s the idea. Usually we use a spectrograph to get the color of the galaxy. This is a device that breaks the light up into thousands of individual colors, allowing a pretty precise determination of the redshift (I’ve done this sort of measurement myself, and it can yield amazingly accurate results). The problem is, something 13.3 billion light years away would be way too faint to see. Let alone measure. But in the case of MACS0647-JD, we had a little help from a few trillion friends.

Let’s Do the Space Warp Today

Take another look at the picture. Almost everything you see in it is a galaxy, a vast collection of hundreds of billions of stars. They’re part of a huge cluster of galaxies called MACS J0647.7 +7015. (I know, that’s awful, but the name’s from the Massive Cluster Survey, with its sky coordinates tacked on.) Now, are you ready for more brain-crushing weirdness? One of Albert Einstein’s big ideas is that that mass literally bends space. The gravity of massive objects warps space, distorting it. Light moves through space and follows that warp, like a car driving along a curvy, hilly road.


^ Close-up of MACS0647-JD,
what may be the most distant
object ever seen. Credit: NASA,
ESA, M. Postman and D. Coe
(STScI), and the CLASH TeamThe light from the distant galaxy MACS0647-JD had to pass through and around that galaxy cluster to reach us. The gravity of the cluster warps space, which acts like a lens, magnifying and brightening the light from the more distant galaxy! We actually call this effect gravitational lensing, and it’s (har har) massively useful, because it allows us to see distant objects that might otherwise be too faint to see. Such is the case here.

So yay, MACS0647-JD is now bright enough to see! Not only that, but due to the shape of the cluster, the light from the galaxy got split up and multiplied; We actually see three images of it in the big picture above. I’ve inset one here, just so you can see it.

But we’re still not done. There’s one more thing to know.

The Blackness Would Hit Me and the Void Would Be Calling

Even though it appears brighter than it normally would, MACS0647-JD is still way too faint to observe with a spectrograph to get its distance. Instead, astronomers did something clever. They used a series of filters to isolate various colors from the object, ranging from blue out to infrared. They even used observations from the orbiting Spitzer Space Telescope, which is designed to see ever farther out into the infrared. If this galaxy really is 13.3 billion light years away, then it must be an incredibly young object. Young galaxies are loaded with very hot, massive stars that blast out ultraviolet light, and in fact dominate the light emitted from such galaxies. If the galaxy is that far away, the expansion of the universe itself will redshift that UV light by a factor of nearly ten, pushing it well out into the infrared.

Sure enough, when they looked at the images from all the different filters, the galaxy is invisible in all but the infrared ones. That’s a pretty convincing sign it really is that far away. I’ll note the same team that found MACS0647-JD has used this same technique with other, somewhat closer objects, and those have been confirmed using spectroscopy. That lends credence to this new result.

So holy wow. This may really be a galaxy at that forbidding distance. Unfortunately, though, the research paper has not yet been published, so I haven’t read it for myself. Still, the team involved is quite careful and almost certainly was meticulous in their analysis. I have little doubt their results are solid. There is still some chance this may be a foreground object masquerading as something more distant, but it seems unlikely.

So, to be fair, we have to say this is a candidate for the most distant object ever seen. And the funny thing is, it’s not terribly likely we’ll find things much farther away! That’s because the farther away we look, the younger the universe was. And when it was only 420 million years old, it had barely gotten started. We might find things a few tens of millions of light years farther away, maybe even a hundred million or so. But the Universe started with a Big Bang 13.73 billion years ago, so that’s a hard limit to how far away we can see.

And knowing its distance we can figure out how big MACS0647-JD is. It turns out to be pretty dinky as galaxies go: It’s only about 600 light years across and has at most a billion stars. Compare that to our own Milky Way galaxy, living large at 100,000 light years across and containing 200–300 billion stars. MACS0647-JD really is a bit of a dim bulb. It’s most likely still in the act of forming itself into a proper galaxy, so we call it a proto-galaxy. Our own galaxy formed from such modest beginnings as this.

But teeny or not, it’s still amazing. We’re seeing it, quite literally, clear across the universe.

Finding objects like MACS0647-JD is critical to our understanding of the universe. They tell us what things were like when the universe was a mere whippersnapper, something that’s very hard to do otherwise. We can learn how much gas was around back then, what stars were like, how galaxies formed, and even how great the effects of mysterious dark matter and dark energy were, about which very little is known. This new galaxy pushes the limits so hard that everything we learn from it is new.

Plus, it’s just so darn cool! Look at it again, it may just look like a lumpy red blob, but it’s telling us a vast amount about the entire universe we live in. Nothing lives in isolation, no scientific fact sits alone. Everything we see, everywhere, has an impact on what we understand. Even a tiny ball of stars 133 billion trillion kilometers away.

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Dust. Wind. Dude. | Phil Plait
Bad Astronomy at Slate dot com | 17NOV12

The other day I posted an amazing picture, showing the output of a computer model displaying a global map of atmospheric aerosols—particles suspended in Earth’s air.


^ Still frame from NASA’s global
aerosol map animation. Image credit:
William Putman, NASA/GoddardFirst, a mea culpa. I said the computer program was used to make climate predictions, but in this case that’s not quite right. It used actual data from Earth-observing satellites to model the transport of the aerosols and calculate their density as they moved around, distributed by winds. Models similar to this are used for climate prediction, but in this specific case it wasn’t. It’s just one step in the process.

And as it turns out, the picture I showed is literally one step in the process: It’s actually part of a series of calculations the program did, modeling the density of the particles over the time period of Aug. 2006 to Apr. 2007. And what do you get if you take these individual images and string them together into a single animation?

You get amazingness. Behold:


[Make sure to set the video to 720p resolution.]

Remember, red is dust, green is soot, white is sulfates (from fossil fuel burning and volcanoes), and blue is sea salt whipped up from the ocean surface.

I annotated the video to point out some interesting bits, like how you can watch the Saharan dust blow west to Florida. I was also amazed when a huge white (sulfate) bloom appeared to the northwest of Madagascar in January 2007, and then found out there was a big eruption of the Karthala volcano at that time. You can also see lots of sulfates (presumably from fossil fuel burning) over the U.S., Europe, and China. Seeing all these aerosols whipped around into cyclonic shapes and moving across land and sea is simply mesmerizing.

When you see the Earth laid out like this, and the particles in our atmosphere swept around, you cannot help but see that no part of the Earth stands alone. Every point on our planet touches every other point in one way or another.

And even if I made an error in that last post, the overall message is still the same: we need to monitor our world. The effect we are having on it is profound, and while we might have difficulty in detail understanding it all, the overwhelming evidence is that we’re heating the planet up, and this is affecting everything. Everything.

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This is my way of saying Thank You to Jeff and for RI. I’m thankful we’re ALIVE to see things that are smaller and much larger than our species. It really is a good time to be living.

~ A.

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To Stand in Awe Before the Universe | Phil Plait
Bad Astronomy | 22NOV12

I’ve been writing about the Universe for many years now. Whether it’s looking down at our home planet or up into the farthest reaches of the heavens, I am in awe of everything about it.

This is what it looks like to live in my head:


^ Self-portrait of photographer Ben Canales (and the Milky Way) on Oregon’s South Sister. Image credit: Ben Canales. Used by permission.

This photo by astrophotographer Ben Canales is everything I love about my job.

Among our greatest assets are human curiosity and our hard-won ability to reason things out. Sharing what comes out of these is a true pleasure.

The most amazing things about the Universe are that we are a part of it, and that we can understand it at all.

[I follow Ben on Google+, where he posts one astonishing photo after another. This one was shot at 3,000+ meters (10,000 feet) atop the South Sister volcano in Oregon.]

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The Hunter and the Meteor | Phil Plait
Bad Astronomy | 23NOV12

Last week was the peak of the annual Leonid meteor shower, when the Earth plows through the debris sloughed off by the comet Tempel-Tuttle, treating the denizens of our planet to a cascade of shooting stars.

I’ve seen a lot of photos from the event, but I should’ve known that my pal Randy Halverson—a gifted astrophotographer and maker of stunning time lapse videos—would take one that would make my jaw drop to my desk.


^ Leonid meteor streaking past Orion.
Image credit: Randy Halvseron, used by permission.

Holy. Wow. You absolutely want to click that picture to embiggen it.

Ignoring the meteor for a moment—if you can!—Orion dominates the frame, with the bright star Betelgeuse glowing orange-red on the Hunter’s right shoulder (on the left in the picture, since Orion is usually depicted as facing us). Someday, almost certainly in less than a million years, Betelgeuse will explode as a supernova, and for a few weeks will be so bright you could read by it.

To the lower left of Orion is Sirius, the brightest star in the night sky. It’s a binary star, two stars orbiting each other, one about twice the mass of the Sun and far more luminous, the other a faint spark of a white dwarf, a dead star too faint to see without a telescope. They’re only about 9 light years away, which is why they appear so bright. Proximity means power when it comes to the starry night. Usually…

But not always. Rigel, the star marking Orion’s left knee (on the right to us) is roughly a thousand light years away and still one of the brightest stars in the sky; that means it’s an actual superstar, over 100,000 times more luminous than our Sun! If it were as close as Sirus, it would be comparable in brightness to the Moon.

So, yeah.

I could go on and on, describing what you see in this picture. Randy shoots most of his work in South Dakota, where skies get very dark. This was on the White River, and he used a 30 second exposure to capture this shot. You can just see the stars trailing a bit in the higher-res version, streaking a little as the Earth turns underneath them, carrying them east to west across the sky. The meteor, though, isn’t blurred because it screamed across the sky in less than a second! It was probably no bigger than a tiny grain of sand, but moving at 70 kilometers per second (40+ miles per second), dozens of times faster than a rifle bullet—fast enough to cross the continental United States in just over one minute. Its tremendous energy of motion was converted into heat, causing the air around it to glow, and the meteoroid (the grain itself) to vaporize.

It was part of a comet for billions of years, found itself freed of that icy domain just a few years ago, then ended as brilliant flash of light and drama in our atmosphere in less than a single second. If there’s a lesson in that, feel free to find it.

And you might think that Randy was lucky to capture this shot, but luck had very little to do with it. He goes outside at night all the time to capture the beauty of the heavens. It’s not luck, it’s inevitability. Go out enough and you will see all manners of amazing things.

Go. Look up. See what there is to see. You’ll be amazed at what’s going on just over your head.

[justdrew]

so we've all seen that old pic showing the macro scale of the universe and the micro scale of brain tissue and how they look so similar. well... that's been expanded on...

"The structure of the universe and the laws that govern its growth may be more similar than previously thought to the structure and growth of the human brain and other complex networks, such as the Internet or a social network of trust relationships between people, according to a new study. 'By no means do we claim that the universe is a global brain or a computer,' said Dmitri Krioukov, co-author of the paper, published by the Cooperative Association for Internet Data Analysis (CAIDA), based at the San Diego Supercomputer Center (SDSC) at the University of California, San Diego.'But the discovered equivalence between the growth of the universe and complex networks strongly suggests that unexpectedly similar laws govern the dynamics of these very different complex systems,' Krioukov noted."

Universe, human brain and Internet have similar structures
Published: Sunday, Nov 25, 2012, 14:56 IST
Agency: ANI

The structure of the universe and the laws that govern its growth may be more similar than previously thought to the structure and growth of the human brain and other complex networks, such as the Internet or a social network of trust relationships between people, according to a new study.

“By no means do we claim that the universe is a global brain or a computer,” said Dmitri Krioukov, co-author of the paper, published by the Cooperative Association for Internet Data Analysis (CAIDA), based at the San Diego Supercomputer Center (SDSC) at the University of California, San Diego.

“But the discovered equivalence between the growth of the universe and complex networks strongly suggests that unexpectedly similar laws govern the dynamics of these very different complex systems,” Krioukov noted

Having the ability to predict – let alone trying to control – the dynamics of complex networks remains a central challenge throughout network science. Structural and dynamical similarities among different real networks suggest that some universal laws might be in action, although the nature and common origin of such laws remain elusive

By performing complex supercomputer simulations of the universe and using a variety of other calculations, researchers have now proven that the causal network representing the large-scale structure of space and time in our accelerating universe is a graph that shows remarkable similarity to many complex networks such as the Internet, social, or even biological networks

“These findings have key implications for both network science and cosmology,” said Krioukov.

“We discovered that the large-scale growth dynamics of complex networks and causal networks are asymptotically (at large times) the same, explaining the structural similarity between these networks,” the researcher asserted

SDSC Director Michael Norman added, “This is a perfect example of interdisciplinary research combining math, physics, and computer science in totally unexpected ways.”

“Who would have guessed that the emergence of our universe’s four-dimensional spacetime from the quantum vacuum would have anything to do with the growth of the Internet? Causality is at the heart of both, so perhaps the similarity Krioukov and his collaborators found is to be expected.

Of course the network representing the structure of the universe is astronomically huge – in fact it can be infinite. But even if it is finite, researchers’ best guess is that it is no smaller than 10250 atoms of space and time. (That’s the digit 1 followed by 250 zeros.) For comparison, the number of water molecules in all the oceans in the world has been estimated to be 4.4 x 1046

Yet the researchers found a way to downscale this humongous network while preserving its vital properties, by proving mathematically that these properties do not depend on the network size in a certain range of parameters, such as the curvature and age of our universe

After the downscaling, the research team turned to Trestles, one of SDSC’s data-intensive supercomputers, to perform simulations of the universe’s growing causal network. By parallelizing and optimizing the application, Robert Sinkovits, a computational scientist with SDSC, was able to complete in just over one day a computation that was originally projected to require three to four years

“In addition to being able to complete these simulations much faster than previously ever imagined, the results perfectly matched the theoretical predictions of the researchers,” said Sinkovits

“The most frequent question that people may ask is whether the discovered asymptotic equivalence between complex networks and the universe could be a coincidence. Of course it could be, but the probability of such a coincidence is extremely low. Coincidences in physics are extremely rare, and almost never happen. There is always an explanation, which may be not immediately obvious,” said Krioukov.

“Such an explanation could one day lead to a discovery of common fundamental laws whose two different consequences or limiting regimes are the laws of gravity (Einstein’s equations in general relativity) describing the dynamics of the universe, and some yet-unknown equations describing the dynamics of complex networks,” added Marian Boguna, a member of the research team from the Departament de Física Fonamental at the Universitat de Barcelona, Spain.

and here's the best comment from the thread on slashdot...

I'm going to have to look up the original paper published by Krioukov, but what was mentioned in the article itself is not news. I imagine this is a consequence of Krioukov trying to explain his findings in laymen's terms.

What the article actually says is a pretty basic exposition of the findings of network science [wikipedia.org] and complex systems theory [wikipedia.org] over the past few years. For those interested in but unfamiliar with these matters, I recommend a volume written a couple of years ago by the physicist Albert-László Barabási [wikipedia.org] called Linked: The New Science of Networks [barnesandnoble.com]. It is written for a wide audience and is a very readable introduction to the subject. Barabási's based argument is that these common network patterns we see in so many environments is a consequence both growth and preferential attachment in systems. Of course, growth and preferential attachment are going to be present in biological and social systems, as well as things like computer networks, and this is at the heart of why we see similar patterns forming (esp. scale-free topologies).

As a historian, I find the findings of network science as its been applied to social systems particularly useful. It helps to explain societal changes in ways that older theories of history, whether deriving from Marxian, Annaliste, Weberian, or other schools of thought, would have difficulty. Further, the study of networks and complex systems is inherently interdisciplinary--and this in a refreshingly honest way rather than the mere "interdisciplinarity" rhetoric that's been present in the academy over the years. For those interested in the application of network science to the social sciences, there is a very nice collection of seminal articles for the field edited by Gernot Grabher and Walter Powell [worldcat.org].

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so we've all seen that old pic showing the macro scale of the universe and the micro scale of brain tissue and how they look so similar. well... that's been expanded on...

The same Dmitri Krioukov, who co-wrote the paper, also presented a four-page paper to avoid a traffic ticket, and he did. Some people just cannot stop writing papers , as Sir Ken Robinson once said in a TED talk.

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Links in original. Highlights mine.

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Angling in on a Massive Solar Eruption | Phil Plait
Bad Astronomy | 25NOV12

Our Sun is a feisty beast.

It’s a roiling cauldron of gas, so hot that electrons in the gas have been stripped away, creating what’s called a plasma. Currents of rising and twisting plasma underneath the Sun’s surface create intense and convoluted magnetic fields, which in turn affect the shape and behavior of the gas. Piercing the surface, these magnetic fields create gigantic loops along which the plasma flows, like beads along the wires of an abacus. Vast energies are stored in these loops, and sometimes they explode. Violently. Very, very violently.


^ Two views of a huge solar eruption from NASA’s twin STEREO spacecraft.
Image credit: NASA/STEREO

That image shows what’s called a prominence, one of these towering arcs of plasma. You can see it clearly in the bottom picture, but where is it in the top one?

Oh, it’s there, but you need a little perspective to see it. These two images were taken by NASA’s STEREO (for Solar TErrestrial RElations Observatory) satellites; twin spacecraft that view the Sun from two widely different angles. One was launched in a way that sent it ahead of the Earth in its orbit (called STEREO A for “ahead”) and the other launched to lag behind (STEREO B, for “behind”).

On Oct. 14, 2012, the spacecraft took the two pictures above. I’ve labeled them to show which is the view from which spacecraft. STEREO A saw the loop from the side, arcing high above the Sun’s surface—about 500,000 kilometers (300,000 miles), judging from the picture. That’s greater than the distance from the Earth to the Moon!

STEREO B, on the other hand, was almost directly above that eruption, so it sees it edge-on, if you will, looking straight down on it. If you take a moment you can match up some features on the Sun in the two pictures; for example, the white twisted spot to the lower left of the eruption near the Sun’s left edge in the upper image can be seen in the lower one as well.

Note that in the top image it’s labeled as a filament, but in the bottom the eruption is labeled as a prominence. Those mean the same thing! Kinda; it depends on your viewpoint. When seen against space, like in the lower image, it’s called a prominence. But when seen against the face of the Sun, like in the upper image, it’s called a filament. That’s a holdover from when we didn’t really understand the Sun very well; the same feature looks very different depending on how you see it. That should be clear from these two images! So the same event has two names, and we still use both.

No matter what you call it, it’s a spine-chilling event. What you’re seeing here is an eruption that launched billions of tons of gas into space at high speed; an explosion releasing the energy equivalent to at least thousands of times the combined nuclear arsenals of every country on Earth! The Sun doesn’t do anything small.

And hopefully, that will give you a little perspective on our nearest star.

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The Immense Beauty of Saturn | Phil Plait
Bad Astronomy | 26NOV12

On Aug. 19, 2012, the hardest-working spacecraft in the solar system, Cassini, was 2.4 million kilometers (1.5 million miles) from Saturn when it snapped this overwhelming portrait of the ringed planet:


^ Cassini image of Saturn and its moon Tethys (upper left).
Image credit: NASA/JPL-Caltech/Space Science Institute

Man, I love these greyscale shots. They’re so moody.

Right now it’s summer in Saturn’s northern hemisphere—though at 1.4 billion kilometers (900 million miles) from the Sun and temperatures of -150 degrees Celsius (-240 degrees Fahrenheit) and lower, the term “summer” is definitely relative—with the Sun shining down on the rings from the north. Cassini was below the ring plane in this shot, looking up at them, so they appear a bit darker than they would if Cassini were above them looking down.

As you can see, Saturn has lots of rings; thousands, in fact! The rings are not solid, but instead composed of countless small pieces of nearly pure water ice, the biggest probably smaller than an average house. Some of the rings are extremely narrow, too: You can see the thin ones silhouetted against the face of the planet itself, looking like piano wires strung across the vast cloudscape.

Just below and to the right of the rings you can see their shadow on the cloud tops of Saturn. I’m fascinated by the play of light and shadow on the rings and the planet, highlighting the complexity of the rings. You can also see some storms in the clouds on Saturn; that dark circular one with the bright rim around it is about 4,000 kilometers (2,400 miles) across—about as wide as the continental United States!

Saturn is big.

So big, I suspect, that you might have missed the tiny spark of light in the upper left. That’s Saturn’s moon Tethys, seen here a little more than half full as it’s lit by the distant Sun. But it’s hardly tiny: It’s nearly 1,100 kilometers (660 miles) across, about the distance from Chicago to Washington, D.C.!

Our sense of size is dwarfed by objects on this scale. And yet, there we are. Cassini has been circling Saturn and flying past its weird moons since 2004, returning vast amounts of data about the planet and its environment. But for all the knowledge gained, and more yet to come, when I see pictures like this I sometimes wonder if the most important thing Cassini has done is shown us how starkly beautiful and immense our solar system is.

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The Ruins of Past, Present, and Future | Phil Plait
Bad Astronomy | 29NOV12

On Mexico’s Yucatan Peninsula is the ancient Maya city of Chichen Itza. Its history reaches back over a thousand years, but it stands in ruins now, long abandoned.

That does nothing to reduce the magnificence of the Temple of Kukulkan, the iconic stepped pyramid standing 30 meters (100 feet) high at the north end of the main city. I visited there in the spring of 2011, and it was awe-inspiring. The architecture is incredible, and to think the Maya built it without even having used the wheel…

My family and I spent a long day there, enjoying ourselves and learning about this amazing civilization. We left in the early evening, but I now rather wish we had stayed a little later to see the stars come out. That's because I received a note from my friend, astrophotographer Stéphane Guisard, with this photo he took of Orion rising over the mighty temple:


^ Orion rises over the Temple of Kukulkan in Chichen Itza.
Image credit: Stéphane Guisard. Used by permission.

You really want to click that to see it in full resolution. The pale light gives the temple an eerie moodiness, and the colors of the stars in Orion are lovely. You can even make out the pinkish glow of the Orion Nebula, hanging below (to the right in the photo) the three bright stars in his belt. That nebula is a gas cloud many light years across and is a factory of star birth; the light from the massive stars born there light up the gas around them, making it so bright it’s easily visible to the naked eye from its staggering distance of over 1,300 light years—13 quadrillion kilometers, or 8 quadrillion miles.

Most of the stars you can see in Orion are young, massive stars, doomed one day to explode as supernovae. The famed Betelgeuse is probably the closest to that eventual fate, already having turned into a red supergiant due to exhausting its supply of fuseable hydrogen fuel in its core. You shouldn’t have any trouble spotting it in Stéphane’s photo; the color gives it away.

It’s funny to think that in a million years, maybe two, all those stars will be gone, exploded, destroyed. But that’s the lesson of Chichen Itza itself, isn’t it? This too shall pass.

And I can’t help but note that the city itself is located on the edge of the Chicxulub (pronounced CHICK-shoo-lube) crater, 180 kilometers (110 miles) across. It’s the impact site of the asteroid that wiped out the dinosaurs, along with a large fraction of all plants and animals on Earth at the time.

The layers of disaster lie thick at Chichen Itza. The land carved by an impact 65 million years ago, the city decaying for centuries, and the stars above it destined to go the way of the dinosaurs as well…

And one final thought. Even the crater from that impact itself has eroded over the eons to the point where it was difficult to find, despite its size. Even disasters suffer disasters, given enough time.

POST 2974

[Allegro]

Highlights mine. Links in original.

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A Swollen Monster in the Middle of a Galaxy | Phil Plait
Bad Astronomy | 29NOV12

Galaxies used to be called “island universes,” a poetic but not entirely inaccurate phrase. In general, each is a collection of billions of stars as well as huge clouds of gas and dust all held together by gravity (there’s also dark matter, too, but we don’t know much about that except that it’s there).

In the 1980s, we learned that every big galaxy has a huge black hole in its center. Our own Milky Way has one that has a mass 4 million times that of the Sun. That’s big for a black hole, but it’s a tiny fraction of the mass of the galaxy, which is about 400 billion times the Sun’s mass. In fact, our central black hole is a bit of a lightweight; the proportion of black hole mass compared to galaxy mass is usually about 0.1 percent, where ours is 0.01 percent.

A few years ago, astronomers discovered that there appears to be a relationship between the mass of the galaxy’s central black hole and the mass of the galaxy’s inner region, called the bulge. A bigger bulge means a bigger black hole. That ratio is interesting: In general, it holds true across a wide range of galaxies. For some reason, properties of the central black hole and the greater galaxy around it are tied together. That’s telling us something about how galaxies form and how they grow, if we can just figure out why they’re connected.

Of course, in every group, someone has to be a troublemaker. Meet NGC 1277, a disk-shaped galaxy about 250 million light years from Earth:


^ Hubble view of NGC 1277, a galaxy with a heart three sizes too big.
Image credit: NASA / ESA / Fabian / Remco C. E. van den Bosch (MPIA)

Astronomers studying this galaxy have determined that its central black hole is a whopper: It has a mass about 17 billion times the mass of the Sun! This may be a record; it’s certainly among the most massive black holes known. The problem is, that’s far more massive than the central bulge of NGC 1277 would suggest the black hole should be. It’s well over half the total mass of the bulge! In fact, the entire mass of the galaxy is about 120 billion solar masses, which means the black hole at its heart is 14 percent of the total galaxy’s mass; compare that to the Milky Way’s black hole mass of 0.01 percent and you’ll see why astronomers were shocked.

So that’s weird. How could that black hole have gotten that massive?

Galaxies form from huge collapsing clouds of gas. Looking at the early Universe, we see most galaxies are small and shapeless, but nowadays many are big, like the Milky Way. We think that they grow by eating each other! Yes, galactic cannibalism. Usually they collide and merge over time, and the two black holes from the two galaxies also merge, forming one bigger black hole. If that’s the case, then the mass of the black hole and the mass of the galaxy itself should grow at roughly the same rate, and be pretty much the same for every galaxy.

For some reason that didn’t happen with NGC 1277. The astronomers were conducting a survey of galaxies, looking at many of them and figuring out the galaxy bulge to black hole ratio. After examining 700 galaxies, they found five others with abnormally high ratios, though none as beefy as NGC 1277. This means there are exceptions to the rule; not many, but they exist. Interestingly, all of them appear to be compact galaxies, smaller than you might expect given their mass. That may be another useful clue… but what that might mean is still unknown.

Still, that’s OK! We’re seeing the tip of the iceberg here, so to speak, showing us that something is going on, and teasing us with what it might be. Scientists love a puzzle.


^ NGC 1277 is in the Perseus cluster of galaxies, and is marked.
Note how much larger the other galaxies are.
Image credit: David W. Hogg, Michael Blanton, and the SDSS Collaboration

And sometimes, it’s the exceptions that force us to examine the rules. We have several hypotheses about why the black holes and galaxies would have correlated masses, but we’re not sure which one is correct. We need outliers like NGC 1277 to shows us which ideas won’t work so that we can either modify them or throw them away and find ones that work better.

How did our Milky Way get to be so big? Why is our black hole so small? Why are others so big? Why is a black hole so terribly important in the structure of a galaxy that’s millions of times bigger? Answering those questions is the payoff we’re looking for, and knowledge is the reward when you gaze into the dark monster that lurks at the heart of every galaxy.

[82_28]

Damn, bro/sis, keep em' coming, Allegro. Those are just some fascinating articles. It makes one wonder whether we truly are on a spaceship. I don't mean that in the "stupid" sense, but in the sense, I have no idea. Earth is such a placid place compared to everywhere else. And that's the very reason we're here. There's some weird thought I am focusing on right now, but I just can't get it into focus. You're awesome, Allegro! Thanks for keeping us up all to speed on the very things that make life worth living -- fascination.

[Allegro]

^^^ Thank You, 82. You’re very generous,
and there’s more fascination coming your way !

[Allegro]

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Blowing the Dust Off a Spiral Galaxy | Phil Plait
Bad Astronomy | 01DEC12

I was digging around the web looking for some info and stumbled on something that really surprised me: a picture of an old friend I had never seen before!

Of course, I’m an astronomer, so when I say “old friend” I mean some gorgeous astronomical object. In this case, it’s the spectacular face-on spiral galaxy M83, also called the Southern Pinwheel, for obvious reasons:


^ Spiral galaxy M83 as seen by Spitzer Space Telescope.
Image credit: NASA/JPL-Caltech

Isn’t that breathtaking? This image was taken by the space-based Spitzer Space Telescope, which sees the Universe in infrared light, outside the range our eyes can detect. It uses filters to distinguish various wavelengths (colors) of IR light, and then astronomers turn them into images we can see by assigning a visible light color to each wavelength. In this case, what you see as blue is actually light at 3.6 microns (a wavelength about 5 times longer than what your eye can see), green is 4.5 microns, and red is 8 microns.

For the most part, warm objects emit light at these wavelengths. But to an astronomer, -170 Celsius (-270 Fahrenheit) is warm! Don’t ask us what “cold” is.

In a galaxy, strewn between the stars, are vast clouds and ribbons of complex molecules called polycyclic aromatic hydrocarbons, or PAHs for short. We also just call it “dust”. This stuff is essentially soot, and it’s created when stars are born, and when they die. Regions where galaxies furiously make stars are littered with this dust, and it warms up due to the nearby stars. It then glows in infrared, and can be seen by Spitzer to make the above picture.

M83’s lovely spiral arms are where all those stellar nurseries are, so we see them festooned with the cotton-candy-like dust emitting infrared light. The picture looks similar, but different, in visible light. Here’s a shot using the European Southern Observatory’s MPG/ESO 2.2-meter Telescope:


^ M83, this time in visible light. Image credit: ESO

The spiral arms are still there, but now you can see the pink glow of gas clouds, and the blue of hot, young, massive stars blasting light into space. Stars give off infrared light too, so you can see some of the same ones in both images (those stars, I’ll note, are in the foreground, in our own Milky Way). I rotated the image to match that of Spitzer so you can compare them. As gorgeous as this is, I think my favorite part of this picture is the two nearly edge-on spiral galaxies in the upper left. M83 is about 15 million light years away, but those two guys are much more distant, hundreds of millions of light years away at least.

And one other thing: take a look again at the Spitzer image. It looks a bit off-center, doesn’t it? Too low? When I cropped the image I thought I had messed it up, but in fact the center of the galaxy is centered in the image. Measure it yourself! It turns out the galaxy itself is a bit lopsided, asymmetric. The bottom half stretches out farther than the top, both in the infrared and visible light images. That’s interesting! Not all galaxies are perfectly symmetric; a nearby galaxy passing by can distort them, for instance.

Resume.

[Allegro]

Highlights mine. Links in original.

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The Shores of the Cosmic Ocean | Phil Plait
Bad Astronomy | 02DEC12

Yesterday, I went all sciencey on a gorgeous picture of M83, a nearby spiral galaxy. What I didn’t mention, though, is that the galaxy we live in—the Milky Way—is pretty similar. It’s a flattened disk with spiral arms, a central bulge of stars, and lots of stars and dust. M83 just so happens to be oriented so we see it face-on, providing us with the spectacular view I described in that post.

But we live inside the Milky Way, so our view of our own galaxy is different. Nothing illustrates that better than a nice time exposure of the night sky, so here’s one of surpassing beauty for you:


^ The Milky Way over Cape Leveque.
Image credit: Mike Salway, used by permission.

This lovely shot was taken by Mike Salway, an amateur astronomer and photographer living in Australia. He shot this at Cape Leveque in northwestern Australia, on the coast of the Indian Ocean. It’s a single 30 second exposure, which was enough to show the Milky Way without overexposing the lighthouse. I like the way the tree reaches in and how the branches are lit. It’s funny how it looks like the Milky Way is coming out of the lighthouse.

That band of light is the combined glow of millions if not billions of stars in our galaxy. Because the Milky Way is a flat disk, and we’re inside it, we see it as a stream across the sky. In the center of our galaxy is the bulge, a roughly spherical mass of perhaps 20 billion stars, and you can see it plain as day in that picture! Littering the plane of the disk are vast clouds of opaque dust (I talk about this in the M83 post as well) that block our view of the stars behind them and leave a dark lane across the Milky Way (and that nifty X pattern right in the center of the bulge).

Salway also took another fantastic picture of the Milky Way, this time at the beach itself:


^ Milky Way over the beach at Cape Leveque.
Image credit: Mike Salway.

Wow. In this one you can see some famous stars like Alpha Centauri (the bright orange one just to the right of center, sitting in the middle of the plane of the Milky Way) and Beta Centauri just above it. A bit farther out along the galaxy’s disk you can see a dark splotch: That’s the Coal Sack, a cloud of dust about 30 light years or so across and about 600 light years away. Immediately above and to the right of the Coal Sack is the constellation of Crux, the Southern Cross. Salway also has a shot of the same scene but with a very bright shooting star called a fireball blazing across. Pretty cool.

It’s amazing what you can see in a photo that’s just half a minute long. It helps, of course, to have the natural beauty of Australia in the foreground and the aggregated might of a massive galaxy in the background.

I sometimes like to think of the Milky Way as a city, with a hustling downtown area toward the center (the bulge) and the spiral arms as the suburbs. Happily for us, we live in a pretty nice part of town that has a fantastic view.

[Note: I stole the title of this post from the title of Carl Sagan’s first episode of “Cosmos.” It seemed appropriate.]