Blogs / Bad Astronomy

Astronomers — even skeptical ones with a sense of humor and an eye for pareidolia — can miss things. In this case, I can hardly believe I somehow dropped the pigskin on this one.

Back in April, I posted an incredibly beautiful picture of sand dunes on Mars taken by the HIRISE camera. Here’s the picture:

Wow. I mean really, wow!

The thing is, I was so drawn to the dunes that I missed something that, in retrospect, makes moi a bit of a fool. Look to the middle right; see that raised dome? Yeah? Well, look a little closer:

See it? Maybe this comparison will help vous.

It’s so obvious! And what makes it worse is as soon as I saw it I knew why it was there… all you have to do is look at this image of the Martian surface taken by the Viking 1 orbiter back in the 1970s…

It’s all clear to me now. It’s not easy being red.

Sigh. Pareidolia is certainly subjective, of course, but as a wise swine once said, "Beauty is in the eye of the beholder and it may be necessary from time to time to give a stupid or misinformed beholder a black eye."

Tip o’ the hand puppet to BABloggee Ken Arthur for notifying me of my oversight. Tip o’ the heat shield as well to the Tampa Bay Skeptics for the Kermit pic.

So by now you’ve probably seen the incredible NASA image of the plume from the volcano Sarychev Peak… but have you seen it…

… in 3D?

Dree! Dree! Dreee!

Apologies to anyone who isn’t an SCTV fan. OOooo! Scary!

I guess this spring retainer from a ‘66 Bronco was happy to be replaced. That’s service with a smile.

Tip o’ the dipstick to Dan.

How do galaxies form?

Seems like a simple question, right? We live in a galaxy — a sprawling city of gas, dust, and over a hundred billion stars — and we see hundreds of billions of them in the sky, so you’d think we have a decent handle on how these objects came to be.

That turns out not to be the case. Their formation is more complicated than you might expect, but a new set of observations reveals an important clue in the birth process of the largest discrete objects in the Universe.

First, the cool image:

OK, so it’s not the most photogenic thing in the world. But what is it?

Deep optical images of young galaxies reveal that they are surrounded a vast cloud of hydrogen gas, many times larger than the galaxy itself. In a fit of nomenclaturial acumen, astronomers have dubbed these "blobs". The thing is, to be seen at all from this great distance, the blobs must be tremendously luminous, and there’s no clear source of energy for them. Something must be powering them, but what?

There were two competing ideas: one was that the gas is simply cooling as it falls in to the galaxy, and that gas radiates away its heat in the form of light (similar to the way a hot iron bar will radiate its heat away as infrared light). That will then power the gas on the outside, causing it to glow. The other idea was that there is some central source of power deep inside the galaxy itself, lighting up the blobs like a light bulb in a smoke-filled room.

But which is it? Ah, enter these new observations.

The image on the left is of such a young galaxy with a blob around it. This image is optical (from Japan’s Subaru telescope and Hubble) plus deep infrared (taken using the Spitzer Space Telescope). You can see the blob, falsely colored yellow, and the denser galaxy embedded in it. Look at the upper left part of the blob: see that reddish glow? What could that be?

The image on the right reveals it. That is the same picture, but added in (in blue) are observations using the Chandra X-ray Observatory. X-rays are only produced through very energetic and violent sources, such as matter swirling around a black hole, or exploding stars. That would certainly explain what’s powering the blobs’ light! But usually these events also produce a lot of optical light. Why don’t we see that?

The reddish glow in the left hand picture is the key. That indicates the galaxy is loaded with dust, made when stars are born and when the explode, too. Dust absorbs optical light, and what does get through can be highly reddened.

So now it looks like we have a complete picture of what’s going on here: as a galaxy forms from an infalling blob of gas a million light years across, a supermassive black hole coalesces in the center. Matter falls in, swirling madly around it, pouring out X-rays. Just outside this central region of the galaxy, stars are born at tremendous rates, creating lots of dust. The most massive stars explode in just a few million years, also blasting out X-rays, but also making even more dust. The dust blocks our optical view of the bright sources, but the X-rays still can leak out in quantities sufficient to heat up and light up the surrounding blobs of gas. What this means for the galaxy at large is that this huge amount of energy dumped into the blobs may slow and eventually reverse the infall, shutting off the process which forms the galaxy itself.

What we’re seeing here may be the last birth throes of a galaxy.

What I love about all this — besides the fact that we can know anything at all about what’s going on in an object a million light years across, billions of light years away, and billions of years in the past — is that we need all these observations together to figure this stuff out. The optical light alone presents us with a mystery, and the IR observations help but don’t solve the problem. But when you add the X-ray observations, they reveal the solution.

And think on this… the blobs we’re talking about here are huge, dwarfing the galaxies that are forming from them. They contain billions of times the Sun’s mass in raw gas, the building material of stars in a nascent galaxy. And these immense clouds are being lit up by not just supernovae — which are terrifying all by their lonesome, dumping out energy at rates that would turn the Earth into a crispy ember — but also by gigantic black holes smack dab in their galaxy’s hearts, which are blowing out energy in quantities to rival or exceed the supernovae themselves.

Yet all that power, the true source of energy illuminating the clouds so much we can see them from across half the Universe, is hidden from our telescopes. Or at least it was, until we learned to slip the surly bonds of Earth and loft our eyes into space, where X-rays can travel freely, unimpeded by our pesky atmosphere.

The universe is complex, and if we truly want to understand it, we will need to continue to explore it, and use the combined might of our scientific equipment to investigate it. There are hidden treasures out there, and the more we probe, the more we’ll find.

All the astronomy sites are buzzing over this amazing image of a sunspot:

Click to embiggen.

I don’t blame them… it’s gorgeous! And it’s not even real! It’s a computer-generated model of the magnetic field in a sunspot; near the center the field lines are mostly vertical and around the edges they are mostly horizontal.

But to me, as a scientist as well as an appreciator of gee-whiz images, it’s this shot that tickles my brain:

Click it to see it cromulently embiggened.

I know, it doesn’t seem like quite as much to look at, but it is: it’s the first time a computer has modeled in detail the magnetic field line strengths of a pair of coupled sunspots vertically, in three dimensions, into and beneath the surface of the Sun!

Wow. You have to understand, magnetic fields are the devil’s own work to model; they’re fiercely complicated. The equations are tough enough to solve, but the field lines interact with one another as the gas moves around, making this sort of modeling just as painfully hard as it could be. We understand quite a bit about sunspots in general, but in detail they are still a mystery; models like this will help us grasp those details. The resolution is incredible; the computer modeled points in the virtual Sun just 10 to 20 miles apart. That meant it needed to keep track of nearly two billion points.

That image is amazing, and beautiful. The way they colored it, it looks like a slice beneath the Earth’s surface… but the width of that image is far larger than the Earth itself. As for the science, check out this animated sequence to see just how this simulation allows scientists to understand the movement of the gas in a sunspot, too. You can see the gas flowing outward from the center, and the convection inside the Sun driving parcels of gas up and down.

Holy crap.

And just as amazing is the computer itself that did this work: NCAR’s Bluefire, which can perform 76 trillion calculations per second.

I’m glad they didn’t name it Skynet.

This comes at a time when we’re starting to understand how streams of gas under the Sun’s surface relates to its overall sunspot cycle. All of this has been a huge mystery for centuries, and we now live in a time of accelerating understanding of the Sun. And, on top of all this, due for launch later this year is the Solar Dynamics Observatory, a highly sophisticated spacecraft that will study our nearest star in better detail than ever before.

This is a great time to be a science geek. Revel in it.

Oh, and to the Plasma/Electric Universe believers who always froth and foam about how "mainstream" scientists don’t understand magnetism and plasma: you’re looking increasingly marginalized, dudes. You might want to look into a new line of work, like UFOs, or 9/11 theories. Science makes progress while pseudoscience makes excuses… and your field ("field"! Oh man, I slay me!) is looking weaker every day.

Herschel, the largest far-infrared telescope ever launched into space, has taken its first image!

Whoa.

That’s M51, better known as the Whirlpool Galaxy, a nearby spiral galaxy (well, 25 million light years is close on an intergalactic scale). It’s face-on to us, allowing us to see its magnificent spiral arms and all the structure therein. Herschel is sensitive to far-infrared light, much lower energy than what our eyes can see. In galaxies, the brightest emitter of that kind of light is dust located near and in between stars, and dust is created by stars when they are born (and when massive ones die). Star birth happens in the spiral arms of these kinds of galaxies, so when Herschel looked at M51 that’s what it saw: the spiral arms outlined by the warm dust within them. The brights spots are where dust is being warmed by young, massive stars. It’s falsely colored blue in the image, meaning it’s the highest energy flavor of IR light Herschel sees; to our eyes it would still be invisibly far in the infrared.

If you’re used to Hubble images, this one looks a little fuzzy. That’s because the resolution of a telescope — that is, how well it can resolve small objects — depends on the size of the mirror and the wavelength of light it sees. Optical light, the kind we see, has a far, far smaller wavelength than infrared, so images in optical light have much higher resolution, and look sharper.

But for science, we want to know how much better Herschel does than previous far-infrared telescopes, and that depends on its mirror. Herschel wins here by a lot: its mirror is 3.5 meters across! Spitzer, the NASA observatory that has been taking such wonderful IR images of celestial objects, has a mirror less than a meter across, so Herschel’s eye is far sharper. Compare!

You can see that Herschel’s view of M51 is a lot sharper than Spitzer’s at these long wavelengths. This means that with Herschel, astronomers will have a better infrared view of the sky than ever before. [Update: To be clear, Spitzer was not optimized for wavelengths this far in the IR, so its resolution in that image above is actually not as good as what it could do at shorter IR regions; for example check out this stunning M51 image taken by Spitzer in the nearer infrared to see what it can do!]

And this is just the first image, a test of the telescope’s abilities. In the coming weeks, months, and years, we’ll be seeing far more from this new eye in the sky, and I am very much looking forward to seeing what it sees.

Tip o’ the dew cap to Amanda. Image credits: ESA and the PACS consortium (Herschel images), and NASA/JPL-Caltech / SINGS (Spitzer image)

Ho-hum. It’s just another GORGEOUS PICTURE OF SATURN’S RINGS!

Holy Haleakala!

The thing is, it’s not just another gorgeous picture. This image — from Cassini, of course — is truly remarkable.

The first thing you should know is that Saturn’s rings are incredibly flat. If you scaled them down to the size of a piece of paper, they’d actually be far thinner than a single sheet of that paper. In fact, even though they’re about 200,000 kilometers across, they are only at most a few dozen meters thick!

But not everywhere.

Daphnis is a teeny tiny moon, just 8 km (5 miles) across. It orbits Saturn inside the broad A ring, and it’s carved a gap in the rings called the Keeler Gap. The gap is about 45 km (25 miles) across. As it happens, Daphnis has an orbit that is not perfectly circular, so sometimes it’s in the middle of the gap, and sometimes near the inner edge. Not only that, but the orbit of the little moon is tipped a bit, so sometimes it’s a bit above the ring plane, sometimes a bit below.

When it’s near the inner edge and also above the ring plane, it pulls the nearby ring particles up out of the ring plane with it. When it’s below the plane it pulls the particles down. When the elliptical motion of the moon is combined with the tilt, the gravitational interaction on the ring particles produces vertical ripples in the ring. These ripples have been predicted in the past, but now Cassini has clearly imaged them for the first time.

Here’s a closer view.

[You can get an even tighter zoom at the Cassini CICLOPS site.]

Right now, Saturn’s tilt is such that the rings are almost edge-on to the Sun (I’ve explained this in more detail in an earlier post). If you stand outside at sunset in a flat area, you can see your shadow stretching for a long way… and the same is true at Saturn. The rings are flat, and the Sun shining almost parallel to them, so any deviation from flatness is obvious by the shadows.

And that’s what you’re seeing in those images. Daphnis is the obvious white lump in the image with the long, black, triangular shadow stretching beyond it. And you can clearly see the ripples it causes in the rings, too! To the left of Daphnis the waves are on the edge of the rings outside the Keeler Gap, and on the right they are on the inside of the Gap. This may seem weird — it threw me for a moment — but remember the rings are made of particles that are traveling at almost but not quite the same speed as the moon itself. The particles in the ring outside the moon’s orbit (farther from Saturn) move a bit slower, and inside the moon’s orbit (closer to Saturn) move a bit faster. So it’s like cars on a racetrack, catching up and passing each other. When Daphnis passes the outer edge particles it pulls on them, and as the particles on the inside edge pass Daphnis they get pulled too. The combined motions are pretty complicated, but add together to produce the effect you see here.

And what an effect: those ripples are big, from 0.5 to 1.5 kilometers (1/3 to 1 mile) high. Even then they’re dwarfed by the immensity of the rings, though, which only rams home the scale of these images.

Incredible.

Saturn’s empire of moons and rings is an amazingly complex interacting system. But the mathematics of it is predictable, since the important factors are basically gravity and the fact that the particles can collide with each other and exchange momentum. Sophisticated computer models can be made which do predict these interactions, and that has been done. These ripples were not only modeled, but predicted to occur with this size before they were observed! John Weiss — Cassini astronomer and a friend– was the lead author on a paper about this:

We thought that this vertical structure was pretty neat when we first saw it in our simulations, but it’s a million times cooler to have your theory supported by such gorgeous images. It makes you suspect you might be doing something right.

True. But of course, that’s the essence of science. Predictions aren’t terribly useful unless they’re borne out by observations, and I agree strongly with John: it’s even better when images this spectacular have your back.

Science! Pleasing to the eye and the brain.