Tag: Cassini

Saturn, surreally

By Phil Plait | May 23, 2012 7:00 am

Take 7+ years of Saturn observations by the Cassini spacecraft, stitch a whole lot of them together into short, film-noir-like segments, and add a Beethoven soundtrack. What do you get? Awesomeness.

The video was put together by Nahum Chazarra, who says on Twitter he’s a "Geology student, science lover". There’s literally too much in this to describe! Moons, rings, the planet itself… but I think my favorite part is when some object, usually a tiny moon, stays centered while the rings and planet and other objects wheel around it. It’s a change-of-perspective effect, but amazing to watch. And you really can’t go wrong with "Moonlight Sonata".

Something like this video has been done before (specifically here and here, and both are well, well worth your time to watch) but to be honest it’s impossible to get too much of this. The changing lighting and exposure, the sometimes jerky apparent motion (due to the inconstant times between exposures combined with the spacecraft’s motion), and the simply jaw-dropping spectacle of the ridiculously gaudy Saturnian system, all combine to make this an engaging and even mesmerizing show.

Tip o’ the dew shield to Dark Sapiens.

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The stark beauty of Cassini’s Saturn
Mesmerizing time lapse of Saturn and Jupiter from spacecraft
An icy Titanic encounter
Video of Cassini’s Hyperion flyby

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: Cassini, Saturn

Ice moon, ghost moon

By Phil Plait | May 10, 2012 8:55 am

One of my favorite things to do is take a gorgeous astronomical image and pierce down into it, finding some detail not discussed in press releases and other articles.

On the other hand, sometimes I’ll post a picture because it’s so, so cool:

[Click to encronosenate.]

That’s a shot of Saturn’s rings and moons by the Cassini spacecraft, taken in mid-April 2012. Cassini was nearly in the same plane as the rings, so they look like a knife cutting across the image. The bright moon is Enceladus, tiny and icy, almost but not quite full as seen from this angle.

But the scene stealer is Titan, the moon as big as a planet — bigger than Mercury, actually — looming in the background, nearly invisible. This image, taken using a filter that only lets through green light, shows just how much darker Titan is than Enceladus. The bigger moon is shrouded in a thick, hazy atmosphere, and reflects about 1/5th of the sunlight that falls on it. Enceladus, on the other hand, is covered in ice, and reflects nearly all the light that falls on it. So the brightness ratio you see here is real: Titan really is far darker then Enceladus.

… and there you go. I drilled down a bit into the picture’s science anyway. I guess I had to. It’s in my nature; when it comes to science, I’m reflective too.

Image credit: NASA/JPL-Caltech/Space Science Institute

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Incredible quadruple transit on Saturn!
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CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Saturn broods while a storm dissipates

By Phil Plait | April 30, 2012 5:48 pm

I’m in the middle of writing up a ton of stuff for the next couple of days, so let me just leave this here: a lovely image of Saturn and its moon Tethys and Enceladus, courtesy of Cassini:

[Click to encronosenate.]

Sigh. So pretty. Tethys is the moon to the left, just above the rings, and Enceladus is right next Saturn, just below the rings. Cassini was just 1° south of the ring plane when it snapped this shot, so they appear very thin. It’s approaching northern hemisphere summer for Saturn, though, so the Sun is shining down on the rings, and they cast a wide shadow on the planet’s southern hemisphere cloud tops.

I can’t help noticing the long, thin, white ribbon of clouds about 2/3 of the way up Saturn’s northern hemisphere. That looks very much like the remnants of the gigantic storm from late 2010 that was so long it actually wrapped all the way around the planet! If you think it’s crazy to think a storm could last that long, take note that Jupiter’s Great Red Spot is at least 350 years old — it was discovered around 1665, and who knows how long it was around before then? And heck, Saturn itself suffered through a huge lightning storm for eight months.

Our gas giants don’t screw around. When they do something, they do it big.

Image credit: NASA/JPL-Caltech/Space Science Institute

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CATEGORIZED UNDER: Astronomy, Pretty pictures

Mesmerizing time lapse of Saturn and Jupiter from spacecraft

By Phil Plait | April 30, 2012 6:29 am

One of the single greatest advantages of the modern age of astronomy, in my opinion, is that digital images from telescopes and spacecraft — and telescopes on spacecraft — have been placed in the hands of everyone. It can take years of training to correctly process and interpret astronomical data, but even without that these images can be put together to make art, scenes of surpassing beauty that professional astronomers might not even think to create.

Dutch video editor Sander van den Berg looked at Cassini and Voyager images, and saw beyond the raw data into the beauty of motion in them. He created a video that is stunning. Stunning. He calls it, simply, "Outer Space".

The events depicted take days, even weeks to play out. Yet somehow, the quick shots and fast cuts — necessary because in many cases there really aren’t very many images to play with — add to the majesty and grandeur of what you see. I suppose that’s no more paradoxical than having canvases far bigger than Earth, yet loaded with detail packed into those vast frameworks.

The Universe is magnificent on every scale, both in space and time. That’s one of the reasons I like working there.

Related Posts:

The stark beauty of Cassini’s Saturn
Video of Cassini’s Hyperion flyby
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Jupiter, the Bringer of Jollity

A shadow falls on the ice geysers of Enceladus

By Phil Plait | April 17, 2012 6:34 am

So on Twitter, my pal Carolyn Porco — imaging team leader for the phenomenal Cassini Saturn spacecraft — announced that a bunch of raw (that is, unprocessed) images were just released from Cassini. Taken on April 14, these new shots show the moons Tethys and Enceladus. I’ve written about Enceladus about thirty two bajillion times, because it’s fascinating, and photogenic as heck. Geysers of water are erupting from its south pole, reaching heights of hundreds of kilometers, with some particles leaving the tiny moon altogether.

And, unsurprisingly, the new pictures do not disappoint, especially this one of Enceladus!

I know. [Click to encronosenate.]

It almost looks like a solar eclipse picture, but the dark circle is actually the night side of Enceladus, with the sunlight coming from the lower left. You can see quite a few geyser plumes, blasting up from the surface to such heights that they’re illuminated by the Sun and we can see them around the edge of the moon.

As I looked at this shot, I suddenly realized something neat: you can see (at least) three dark arcs across the geysers — I’ve used arrows to point them out in the inset picture. These arcs are actually shadows being cast by the moon itself! The curved edge of the moon’s horizon casts a shadow into space, and where it falls across the geyser plumes it reveals itself as a dark, curved line.

What’s so very cool is that you can see the arc of the shadow edge on the upper left — what I’ll call the first arc — is actually higher off the limb of the moon than the one lower on the right (the third one is closer to the limb of the moon under the first arc).

Why is this cool? Because it tells us where those shadows are falling on the geysers. In other words, it’s 3D info on the geysers for free!

Read More

The look of a Titanic moon

By Phil Plait | April 12, 2012 9:30 am

Astronomical imaging is an interesting process. The most common question I get when I show a picture is, "Is this what it would look like if you were actually there?"

That’s a tough question to answer in many cases, because our eyes see in a different way than cameras take pictures. We have receptors in our eyes that are sensitive to red, green, or blue light, and they send signals to the brain which then constructs a "true color" image from that. In astronomy, we use filters to mimic that, but they don’t actually perfectly represent the way our eyes see. And even after you get the picture, there are adjustments in contrast, brightness, and so on that can alter a photo.

A few months ago, the folks at Cassini released a really cool picture of Saturn’s moon Titan. It’s a great shot, have no doubt, but amateur astrophotographer Gordon Ugarkovic — who has some experience putting together color pictures from Cassini images — felt that processing the image in a different way might represent natural color better. So he reprocessed it, producing this amazing image:

[Click to encronosenate.]

All by itself, that’s a stunning shot. Titan is larger than Mercury, but still dwarfed by the gigantic planet it orbits. Titan has a thick atmosphere, and you can see some details in it, like the "polar hood" over its north pole. Also, a really neat effect is on Saturn itself. You can see the rings, as well as the shadow of the rings on Saturn’s cloud tops (below the rings themselves). Near the edge of Saturn, the shadow dips downward, hooking down a bit. That’s a product of several effects, including refraction; the bending of light as it passes through the atmosphere (similar to why a spoon looks bent in a glass of water).

It’s interesting to compare Gordon’s version to the one released by Cassini as well (shown here; click to embiggen). Both are beautiful, interesting, and show a lot of detail. The "official" release is darker, a bit, which is the most obvious aspect. Gordon’s shows details in Titan’s polar hood better, but I see more subtle variations in Titan’s atmosphere overall in the official shot, and perhaps better detail in the ring shadows, too.

So which one is better? Neither! They both are amazing, and show slightly different things. One might appeal to you more in an aesthetic sense, or in a scientific sense, or because you’d rather see details in Titan versus Saturn, or whatever. But in my opinion, it’s OK to like both or neither or one over the other for whatever reason you prefer.

In astronomical imaging — something I did professionally for over a decade — the image is never really what you’d see if you were there, because the instant you use a camera and a telescope you’re already two steps removed from real vision. You can try to get as close to what the human eye would see as you can, but I think in most cases that’s a conceit, something that’s interesting to our minds but perhaps not our eye.

And like all photography, this is art. If you want to display an astronomical object and are being true to what you are showing, then it’s OK. These images done for press releases or simply for their own sake are meant to inspire our imagination, fire up our curiosity, and see their beauty.

Beauty that is, at the very least, in the mind’s eye of the beholder.

CATEGORIZED UNDER: Astronomy, Pretty pictures

A moon casts a looooong shadow

By Phil Plait | April 10, 2012 12:00 pm

On January 21, 2012, the Cassini spacecraft was about 2.5 million km (1.6 million miles) from Saturn when it took this shot of the planet’s clouds:

That long, distorted black smudge is actually the shadow of Mimas, one of Saturn’s moons! Mimas was way off to the side when this picture was taken, so the shadow it cast was stretched out due to the curvature of the planet itself. Think of it this way: if Mimas had been directly between Saturn and the Sun, the shadow would be a nice circle right in the middle of the planet’s face. But because it was off to the side, the shadow happened to fall where the planet was curving away, so it got elongated.

This has been seen many times before by Cassini as Saturn’s fleet of moons dance around the giant planet. Here’s one from Titan, and another from tiny Epimetheus casting a shadow on the rings!

In the image I noticed a faint, circular feature above and to the right of the shadow that looked like either a storm or perhaps a camera defect — sometimes dust in the camera makes circular donut shapes in the pictures, which have to be corrected. So I went to the Cassini raw image database and found the shot — it’s real! It’s a storm of some sort, and it just didn’t show up well in the first picture (note I had to rotate the image to match the one that was released of Mimas’s shadow). What’s funny is, you can see one of those small donuts in the picture, off to the left!

Pretty cool. And I love that the raw images are so accessible, so if someone has a question like that, in many cases the answer is just a few clicks away.

Images credit: NASA/JPL-Caltech/Space Science Institute

Related Posts:

Saturn’s rings cast long shadows
Side view of a Death Star moon
Titan’s shadow
Watch Saturn’s shadow dancing

MORE ABOUT: Cassini, Mimas, shadow

Desktop Project Part 10: The crescent and the plume

By Phil Plait | April 4, 2012 11:00 am

[Over the past few weeks, I’ve collected a metric ton of cool pictures to post, but somehow have never gotten around to actually posting them. Sometimes I was too busy, sometimes too lazy, sometimes they just fell by the wayside… but I decided my computer’s desktop was getting cluttered, and I’ll never clean it up without some sort of incentive. I’ve therefore made a pact with myself to post one of the pictures with an abbreviated description every day until they’re gone, thus cleaning up my desktop, showing you neat and/or beautiful pictures, and making me feel better about my work habits. Enjoy.]

With planetary pictures, angle is everything. If you have your back to the Sun and face your target, it’s fully lit, and looks like a disk. But if you go around to the other side, and put your target between you and the Sun, it becomes a crescent. Get the angle just right, and that crescent gets very thin…

… which is a view of Saturn’s moon Enceladus we can never get from Earth, but one that the Cassini spacecraft gets all the time. And it’s way, way cool:

[Click to encronosenate.]

But there’s an added bonus here, one that makes this picture that much more amazing: that fuzz at the bottom? Those are enormous geysers, towering sprays of water blasting out of cracks in the surface of the moon and reaching upward for hundreds of kilometers!

We’ve seen the geysers before, and in fact Cassini has flown through them to find out what they’re made of (turns out water laced with lots of organic goodness like acetylene, formaldehyde, and much more). They’re very dim, but easy to see when backlit by the Sun like this.

So we know Enceladus must have liquid water under its surface, to feed these geysers. But is it local, like a subsurface lake, or is the ice of the moon floating on a global ocean? New studies of the cracks from which the geysers emanate seem to indicate the water is everywhere! The geysers are formed from gravitational stress when the moon nears Saturn in its orbit, and the size and shape of the cracks really make it look like the water source is a global ocean, like Jupiter’s moon Europa.

Isn’t that amazing? We can learn a lot about a tiny, icy, backlit world, just by tasting its water.

Image credit: NASA/JPL-Caltech/Space Science Institute

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CATEGORIZED UNDER: Astronomy, Pretty pictures

Worlds bigger than worlds

By Phil Plait | March 1, 2012 7:00 am

Because I love each and every one of you, here is a fantastic portrait of two worlds: Saturn and its ginormous moon Titan, courtesy of the Cassini spacecraft:

Isn’t that breathtaking? [Click to encronosenate.]

I love the panoply of shadows from the rings on the cloud tops of the gas giant planet, clearly showing Saturn has not one big ring, but thousands of thin ringlets. You can also see subtle patterns in the clouds as well. If you look very closely, you’ll see the shadow of the moon Prometheus on the left just below the ring shadows — the moon itself is the white speck just above the rings to the right, just to the right of Saturn’s limb — as well as the shadow of the moon Pandora on the right below the rings. Pandora itself is well outside the frame of this shot though.

Of course, fuzzy Titan looms of the planet’s edge on the right as well. Titan is huge, bigger than Mercury, and if Saturn weren’t there might be considered a planet in its own right. But definitions aside, Titan is a varied and complex place, worthy of intense study. It has weather, lakes of liquid methane, dunes blown and sculpted by wind, and boulders made of water ice harder then rock is on Earth.

Who wouldn’t want to take a closer look at a world like that?

Image credit: NASA/JPL-Caltech/Space Science Institute

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CATEGORIZED UNDER: Astronomy, Pretty pictures

The staring eye of a crescent moon

By Phil Plait | February 10, 2012 10:39 am

Sometimes, the images from the Cassini Saturn probe are so cool it’s tempting just to post them and say, "Look at THAT!"

See what I mean? [Click to gigantesenate.]

But of course, I can’t just leave it at that. This image, taken on January 4, 2012, is a bit different than most. Sure, we see Saturn’s magnificent rings, nearly edge on from this perspective. And we’ve seen this icy moon Enceladus many, many times (see Related Posts below for tons more pictures). Look at the bottom of the moon: see those fuzzy streaks? Those are geysers of water spewing from cracks in the moon’s south pole! Cassini has been studying them intently ever since they were discovered; they are proof that liquid water exists under the surface of Enceladus, though it’s still being argued over whether it’s in pockets, like lakes, or the whole moon has an ocean of water under the surface.

Despite all that, I keep getting drawn to the crescent shape itself. We can never see that from Earth. Saturn is much farther out from the Sun than we are, and geometry demands that from home we always see these worlds nearly fully lit by the Sun. The only way to see them like this is to go there.

But also, that giant circular feature is really interesting. It’s big, maybe 200 km (over 100 miles) across, and a bit darker than the surrounding surface. I tried locating it on an atlas of Enceladus, but it wasn’t obvious at all. I thought it might be an impact basin, but a little scrounging online led me to a paper by Cassini imaging team leader Carolyn Porco, which says there are no large impact basins on Enceladus! So what is it?

Well, why not go to Dr. Porco herself? I sent her a note, and she kindly replied. That region is called Diyar Planitia, and it stands out among the surrounding terrain because it’s much smoother. It does have narrow surface features, but they’re too small to be seen at this resolution. At the low angle at which we’re seeing it here, it looks a little bit darker than the rougher terrain around it, so it’s easier to see (which is why on an atlas it’s harder to find). It is roughly circular, but that may simply be coincidence. Enceladus has been massively resurfaced, with some areas much older than others, due to various forces under the surface — looking this all up I learned a new one, called diapirism, where lower density material underneath higher density material can rise up and break through. That’s one process that’s helped change the surface of Enceladus over the eons.

That’s pretty nifty. And think about that! Today I learned of what is to me a new region of the solar system, one that has an interesting and complicated history, molded by vast forces over long-stretched times, one of which was also new to me. How wonderful to get all that from what’s otherwise just a pretty picture!

But of course, in science, there’s no such thing as just a pretty picture. Science is a tapestry, a vast complex fabric interwoven with countless threads. Each of those threads is amazing, each important, and each leads to another. And that’s where the true beauty of science lies.

Related posts:

Enceladus sprays anew!
Enceladus fires on Alderaan
Saturn weather forecast: rings, with light rain from Enceladus
Icy moon and distant rings


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