Saturn and Us

July 19, 2013 was a very special day in the history of humanity. From a distance of 898.414 million miles (1.445858 billion kilometers) from Earth, the Cassini spacecraft made this stunning mosaic of the ringed planet as it eclipsed the Sun. The result is nothing less than breathtaking:

Saturn, in all its majesty. Photo by NASA/JPL-Caltech/SSI

There is simply no way to adequately convey the beauty of this image in mere words. Instead, I invite you to view the colossal 9000×3500 pixel mosaic itself. Take a moment for it to load and just scroll around for a while. (Be sure to check out the annotated version of the mosaic as well.)

Cassini was “behind” Saturn in the sense that it was on the side of Saturn opposite the Sun. This gave the Cassini team an opportunity to create a mosaic of the entirety of Saturn and its rings backlit by the Sun.

The planet itself appears in silhouette, but not completely. Notice that part of Saturn’s dark side is illuminated by light reflected off the rings themselves. In other words, “Ringshine.”

"Ringshine" on Saturn's night side. Photo by NASA/JPL-Caltech/SSI
“Ringshine” on Saturn’s night side. Photo by NASA/JPL-Caltech/SSI

Cassini was about 17 degrees below the plane of the rings, allowing the rings to appear as an ellipse in this view. And that’s a good thing because it really allows us to explore the rings in a very unique way.

Enceladus with its geysers of ice crystals, creating its own silhouette. Photo by NASA/JPL-Caltech/SSI
Enceladus. Photo by NASA/JPL-Caltech/SSI

The outermost E-ring appears diffuse and ghost-like. It’s created by geysers of ice crystals erupting from Enceladus. If you zoom in on the left side of the image, sure enough you’ll spot Enceladus with geysers erupting!

There are several other moons to be seen in this image, and some background stars as well. But as amazing as this image is, what makes it truly interesting is that you, me, and everyone on Earth are in it.

The day Earth smiled

At the bottom right of the mosaic is a tiny pale blue dot. That’s us. That’s you and me and the whole of humanity right there on a tiny, pale blue dot.

Us, in the distance. Photo by NASA/JPL-Caltech/SSI
Us, in the distance on the lower right. Photo by NASA/JPL-Caltech/SSI
Earth and Moon. Photo by NASA/JPL-Caltech/SSI
Earth and Moon. Photo by NASA/JPL-Caltech/SSI

We are 898.414 million miles (1.445858 billion kilometers) in the background in this image. Zooming in reveals both our home planet and Moon. That’s all of us, right there, looking up toward Saturn, and smiling.

That’s what makes this image of Saturn so special, and why July 19, 2013 is a special day in the history of humanity. Human beings from all over that blue dot looked up toward Saturn while Cassini was taking its picture, smiled, and waved.

I was so happy I could take part in that opportunity to wave at Saturn with my wife, one of my closest friends, and the wonderful people of the Launch Pad Astronomy Workshop.

The class of 2013 from left to right: Jennifer Campbell-Hicks, Claudine Griggs, Douglas Dechow, Jay O'Connel, Jennifer Marie Brissett, Brenda Clough, Jamie Todd Rubin, Liz Argall, Andy Romine, Caren Gussoff, Chaz Brenchley, Jeri Smith-Ready, Anna Leahy, Doug Farren. Kneeling in front: Andria Schwortz, Me, Mike Brotherton
The class of Launch Pad 2013, waving toward Saturn. Our photographer even stood up on a rock so we’re actually looking straight along the line of sight toward Saturn 🙂

Here’s looking at you, Saturn!

Update 2013-11-14: Emily Lakdewalla from the Planetary Society has an excellent walkthrough of the image and explains why things appear the way they do in the image. It is well worth your time to have a watch (be sure to go full screen and HD so you can really spot the details):

An Overhead View of Saturn

On October 10, 2013, the Cassini spacecraft took an image of Saturn that is unlike anything we’ve ever seen from Earth:

Overhead View of Saturn
Saturn captured by Cassini in red, green, and blue-filter images on October 10, 2013. Click to enringulate. Image credit: NASA / JPL / SSI / Gordan Ugarkovic

It’s unlike any view of Saturn we’ve ever seen from Earth because it’s a view we can never see from Earth! Cassini captured Saturn and it’s rings from high above the planet’s northern hemisphere on October 10, 2013. The image shown here is actually a composite of several mosaic images of Saturn and its rings taken in red, green, and blue filters.

And what an image it is! In a rare glimpse we see Saturn as its own planet, detached from its rings. Of course, we already knew that about Saturn, but seeing it this way seems to add a whole new…well…perspective.

The image reveals some striking features of the planet. At the north pole is a 1,250 mile-(2,000 kilometers) wide vortex with wind speeds up to 330 mph (150 meters per second). There’s no land mass on Saturn to break this storm and it’s likely that it’s been there since long before Cassini ever arrived, and will probably remain there for  centuries  to come.

The storm sits at the center of a complex region known as the hexagon, shown in light blue in this image.  Each side of the hexagon is over 8,600 miles (13,800 km) in length – more than the diameter of Earth itself! For some reason though, there is no similar hexagon in Saturn’s southern hemisphere.

Looking at the rest of the image, the first thing that jumped out at me was that you could still clearly see the night side of the planet. That’s because Saturn is being illuminated by the rest of the ring system itself!

Had they been able to, I’m sure NASA would have processed the images and shared it with the public in a press release. But due to the government shutdown, no image was produced. Fortunately, the raw data is public and  Gordan Ugarkovic at created this spectacular image on his own initiative.

On a personal note, I’m extremely grateful for this image because it was taken on October 10, my birthday. So thank you Cassini, and thank you Gordan for an amazing birthday present! 🙂

Waltz Around Saturn

Around Saturn
‘Around Saturn’ by Fabio Di Donato

It’s hard to believe that the Cassini spacecraft has been in orbit around Saturn for nearly a decade now, returning one amazing image of the ringed world and its moons after another. The images are nothing short of breathtaking, but often only become so after some careful work has been done by humans here on earth to remove artifacts, add colors, and general image processing that must be done to make sense of astronomical data.

But there’s a kind of gritty beauty in the raw, unprocessed images as well, so when filmmaker Fabio Di Donato synced them to Shostakovich – Jazz Suite No.2: VI. Waltz 2, the result is a thing of beauty:

Around Saturn from fabio di donato on Vimeo.

I’ve been watching this video over and over again for the last several days and every time I do, I see something new in it. The intricate patterns of the ring system, it’s outer F-ring being deformed by Prometheus, Mimas floating by, the spongy texture of Hyperion, and the eye of Iapetus give the feel that the moons of the Saturn system are all in a kind of cosmic dance.

And what a beautiful dance it is! The whole thing looks like something directed by Stanley Kubrick and David Lynch using a silent film-era movie camera.

The whole video is a joy to watch, and a beautiful portrait of exotic, alien worlds right here in our cosmic front yard.

Stop Calling Them “False Color” Images!

Last week we discussed astronomical imaging and even had our workshop attendees have a go at processing images. Such an exercise is instructive because it crystalizes the idea that colors in astronomical images are neither real nor false. Instead, they’re representative of the filters, structure, and anything else astronomers are trying to pull out of the image data.

Afterward we had a discussion about what the term “false color” really means and that perhaps the term “false” isn’t a very good term to use to describe enhanced images. The discussion turned out to be rather timely because astronomer and imaging scientist Robert Hurt just put a blog post up today where he criticizes the use of the term “false color”. In it, he suggests that the term was invented in a much more mature time when the public had a favorable view of and trust in scientists. Since then, he conjectures, public support and trust of science has fallen flat and the term “false” now implies something intended to be misleading and deceitful. I’m curious if there is any hard polling data that supports or refutes this claim, but I do not disagree with the concern here.

Before I show you what I mean, let’s consider the fact that our eyes only see a tiny sliver of the electromagnetic spectrum

We can only see a teeny tiny part of the electromagnetic spectrum, so how are we supposed to represent the colors we cannot see in an image we're supposed to look at?
We can only see a teeny tiny part of the electromagnetic spectrum, so how are we supposed to represent the colors we cannot see in an image we’re supposed to look at?

As you can see, all of the colors you and I will ever be able to perceive, from the deepest violet to the reddest red imaginable, occupy just a teeny, tiny sliver of the entire electromagnetic spectrum. There are all sorts of colors we’ll never be able to see with our eyes, but we can still detect them with modern-day instruments. These instruments were first showed off to the public during the Voyager missions to the outer planets in the late 1970’s and 1980s. Consider this lovely image of Saturn:

Three Voyager 2 images, taken through ultraviolet, violet and green filters, were combined to make this photograph. And no, it isn’t false, it’s just translated into something we can see. Image credit: NASA/JPL

Pretty isn’t it? Obviously, that’s not how Saturn would appear to our unaided eye if we were flying by along with Voyager, but Voyager captured it in ultraviolet, violet, and green filters. Good for Voyager, but our eyes are simply not capable of pulling off such a stunt. So how can we visualize what Voyager recorded? The answer is to substitute a color we can see for a color we cannot see (in this case, perhaps swapping red in for ultraviolet). This technique doesn’t hide the ultraviolet; quite the opposite – it shows us where the ultraviolet light is coming from!

So let’s describe such images as being rendered in representative color or translated color instead of false color because those colors aren’t being used to falsify anything.

And when we do capture objects in the same colors we do see, perhaps we could refer to those images as being rendered invisible color:

Hubble Space Telescope image of Saturn, processed to appear very similar to how it would look to our eyes. Image credit: NASA/ESA

Even the press release refers to this as Saturn in Natural Colors. Natural to to you and me, perhaps, but what about a Mantis Shrimp? It can see in color bands far beyond the visible and I’m pretty sure he’d be feeling pretty shortchanged if all he saw of Saturn was this washed out-image. Perhaps a better term for this would be Saturn in visible colors instead of in natural colors. Because let’s face it, ultraviolet and infrared happen in nature, too.

All of this is to say that the colors in astronomical images are real, but they may just be being used to represent a color we cannot see with our eyes that nonetheless reveals something truly amazing about the subject in question.

Bottom line, there are no “false color” images and there are no “true color” images. There are only images that convey the wonders of the cosmos to our woefully limited eyes, so let’s drop those false terms once and for all, shall we?