Saturn’s Thin Blue Line

By Phil Plait | May 31, 2005 8:23 pm

I remember when I first looked through a telescope. I was four or five years old, and my dad bought a real el-cheapo department store ‘scope (A Tasco 40 mm for those keeping score at home). He set it up in the driveway, and pointed it at a star in the sky. When I looked through it, I saw it wasn’t a star, it was Saturn.

I still remember the amazement I felt (though the memory has dimmed with time, so I wonder now if the memory has been gilded with the emotions I have felt during the many times I have seen Saturn since). For a first-timer, nothing beats Saturn through a telescope. Nothing. It is a perfect jewel, a wonder floating in a sea of black. The rings are so obvious, and so geometrically wonderful. Whenever I show someone Saturn for the first time, they universally gasp in awe, and the most common thing I hear is “It looks just like it does in pictures!”

Saturn is a very cool place.

And the Cassini space probe just keeps hammering this point home, time and again. The images we’re getting from that machine are truly awe-inspiring. But there are so many! It’s returning thousands of images, far too many for the scientists to look at in real time.

Enter the internet. NASA did a smart thing: they put up a web page where they store every single raw image from Cassini. Anyone with access to the internet can browse these images, or download them and process them– the raw images are not in color, but with a little knowledge and practice, they can be combined to make color images.

That’s just what Spanish amateur astronomer Fernando Garcia Navarro did. He found some astonishing images of Saturn from Cassini, and combined them to form this jaw-dropper of an image:

Click the image to go to a higher-res image, or here for a super-high-res image.

For sheer beauty and awe-inspiring goodness, this is hard to beat. But wait! Where are the rings?

Look closely, and you’ll see them– they are edge-on, so they’re almost invisible (they’re the original “thin blue line”!). When Cassini crosses the plane of the rings, it sees them edge-on, and they nearly disappear. Saturn’s rings extend well over a half-million kilometers from the planet, making them comfortably bigger than the Moon’s orbit around the Earth… yet in most places they are less than a single kilometer thick! To give you an idea of just how thin this is, take a piece of paper and draw a circle on it 20 centimeters across (about 8 inches). If that circle represents Saturn’s rings, then to scale, that paper is 1000 times thicker than Saturn’s rings!

Amazing. Yet they still cast that magnificent shadow across the planet. And if that weren’t enough, two of Saturn’s moons can be seen in the image as well. And one other thing– most people spend so much time looking at the rings, that they never look at Saturn itself. In this image, you can see that Saturn is clearly non-spherical. It’s flattened, wider at the equator than at the poles, because it spins so rapidly (its day is only about 10 hours long) and also because it is very low density. These combine to make the planet 10% wider at the equator than at the poles!

I’ve said it before, and I’ll say it again– Saturn is a very cool place.


Comments (15)

  1. Philippec

    This is why I come here often. Without The Bad Astronomer, I would never get to see such beauty.

    Thank you!!!!


  2. We are very happy that the spell- binding images we have collected from Cassini are being enjoyed by everyone. And it makes our efforts over the last 15 years all the more worthwhile.

    I would like to point out, so that there is no confusion on this matter, that the particular `color’ image you have chosen to display is not the true color of Saturn. CICLOPS, the lab where the images are officially processed for release to the public, has gone to great pains to try to reproduce true color whenever possible on the website. It is not an exact science, but we do the best we can.

    Thanks again for expressing your interest and shared wonder at the beauty of Saturn. For many of us, it was our first `cosmic connection’ and only continues to inspire now that Cassini has settled into orbit.

    Stay tuned for more….
    Carolyn Porco
    Cassini Imaging Team Leader

  3. Michelle Rochon

    Yea, I remember the first time I watched Saturn through that old cheap telescope a friend of dad’s let me borrow… It didn’t look big at all, and my parents could barely make out the rings and planet since the eyepiece did not magnify much… But I could easily see the gap between the planet and the rings through the scratches and the incredible amount of dust. And a lovely little goldish color. Jupiter was looking good too. Much bigger, of course.

  4. I remember seeing Saturn for the first time through a telescope and I couldn’t believe they were real…the rings! Thanks to NASA and The Cassini orbiter it’s confirmed :)

  5. CR

    I still have my cheapo 30x department store telescope from when I was 7 years old (something like 3 decades ago); I use it to show Jupiter’s moons & details on Earth’s moon to kids.

  6. Wow, Carolyn Porco posted to my blog! Kewl. For those of you who don’t know her, she is a mover and shaker in the planetary science community (Carolyn, if you are still reading this, we had lunch together in Boulder a few years ago when I was visiting Dan Durda at SWRI).

    I didn’t talk about true versus false color in this entry, but I guess I can point out that Saturn is not brown. :-)

  7. Wow- I made the image my background and it neatly splits my desktop icons in half. 😛

  8. JusANuttaBackYahdah

    So true, Saturn is cool…doesn’t matter what else I may be looking at… if it’s in the sky…I’ve got to take a peek….thanks for a great blog BA!

  9. Bob Allee

    Ahh, the wonder and exitement of my 1st viewing of Saturn returns. The loveliest view in a small telescope. I often wish I could share this with Galileo, he never really saw or understood the rings through his primitive 4X telescope because they looked more like an unexplainable blur.

  10. Ajith

    Thanks for igniting an interest in our cool neighbors. I’ll be buying my first telescope soon. Thanks again for your wonderful blog.

    Bangalore, India

  11. Len

    >I’ve said it before, and I’ll say it again– Saturn is a very cool place.

    Alright, you’ve convinced me. How much for a round trip ticket?

  12. Saturn is the first planet I look for in the night sky when Im outside on a clear night. To this day it still thrills me, makes me smile and makes me long to see it from space. I’m sending the pic to my brother and also making it a background for my screen.
    Thanks Phil and nice work.

  13. yasmin

    i am doing my talk on saturn i dont have much info

    if u have info email me at


  14. i was looking for a comment on the color. most images of saturn are peach and with cassini blueish at the northern pole… which I THOUGHT was due to color filtering through the rings but recently read that the peach clouds have actually dissapapted due to saturnian winter and the ring shadows making it colder in the north. so saturn really does have blue skies up north right now!

  15. Joe

    As an amateur astronomer (and astrophotographer), who has been studying the science since I was 5, I readily admit that I view Saturn as often as possible. The views that are attainable with today’s scopes and CCD cameras far surpasses Planetarium pictures from just a few decades ago.



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