The scale of Saturn

By Phil Plait | December 19, 2011 10:45 am

With the Cassini spacecraft orbiting Saturn and making frequent fly-bys of all the weird moons there, it’s easy to post one incredible close-up after another. But sometimes, you have to take a step back and get some context, see the bigger picture.

Cassini can do that, too. And when it does, the beauty and scale of the Saturn system is simply breathtaking:

[Click to encronosate.]

This image shows, of course, the ringed planet itself, with the rings seen edge-on and their shadow cast across the planet’s southern hemisphere cloud tops. But look to the left, just below the rings; see that half-lit disk? That’s Enceladus, an icy moon of Saturn. It’s about 500 km (310 miles) across, which may start to give you an idea of how much area this picture covers. Even though it’s as big as my home state of Colorado, it’s positively dwarfed by the looming presence of Saturn behind it… and we’re not even seeing very much of the planet here! Saturn is over 120,000 km (75,000 miles) across, nine times the diameter of Earth.

Saturn is big.

To pound this home, look even farther to the left of Enceladus. See that black speck? I’ve enlarged the picture and annotated it here; the arrow points to Epimetheus, a lumpy gray potato moon of Saturn. It’s about 113 km (70 miles) long. That’s small for a moon, perhaps, but on a human scale it’s a huge rock, more than ten times the height of Mt. Everest.

Yet it’s a speck in this picture, easily missed if you didn’t know it was there. But I guess that’s not surprising; Cassini was 1.2 million km from Saturn when it took this shot, three times the distance from the Earth to the Moon!

Sometimes people ask me, what’s the one thing you wish people understood better about the Universe? And if I had to pick just one only, it would be this: scale.

The Universe is huge, and we’ve barely dipped our toes into it.

Image credit: NASA/JPL-Caltech/Space Science Institute. Tip o’ the meterstick to Carolyn Porco.

Related posts:

An icy Titanic encounter
Enceladus fires on Alderaan
Saturn weather forecast: rings, with light rain from Enceladus
Enceladus sprays anew!

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (55)

  1. We are definitely in need of a Total Perspective Vortex.

  2. Fan of both BA and DA

    “Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”
    Douglas Adams, The Hitchhiker’s Guide to the Galaxy

  3. JenW

    Part of why visiting the Hayden Planetarium is so great is the presentation of scale in the Rose Center. Comparing one item to the next. It helps wrap your brain around it all.

  4. Douglas Troy

    Why do I suddenly feel like a Who in Whoville … I’m tempted to scream “We are here!”, but I heard Stephen Hawking suggests we shouldn’t do that.


  5. It’s nice to see something big actually looking big. :-)

    Should anyone be interested, here’s my own attempt at understanding the scale of the universe, via inch-to-the-mile maps of inch-to-the-mile maps: (By the time we get to galactic scales, the earth ends up smaller than a hydrogen atom.)

  6. Amos Zeeberg (Discover Web Editor)

    Every kid should be subjected to repeated viewings of Powers of 10 (perhaps an updated version) until they get it.

  7. I just did some quick calculations and, were the Earth in that photo, it would take up about 78% of it. That doesn’t sound too bad until you realize how tiny a portion of Saturn that is. It’s a great big Universe and we’re all really puny…

  8. @Amos Zeeberg (Discover Web Editor),

    I always liked the one where you could slide from the tiniest of scales (the space-time foam) to human scales to the size of the Universe. Sadly, I’ve lost the link to that site. I’m sure someone else will have it and be able to supply it, though.

  9. Ksessoking

    I feel so little!

  10. @TechyDad

    I think the web that you’re looking for is this one:

    The scale of the whole universe, from the Planck’s length to the estimated size of the Universe.

  11. David Breece

    I think the Hitchiker’s Guide to the Galaxy covers it pretty well:

    Space,” it says, “is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space, listen…”

  12. Gregory Ruderman

    @Celsius1414: We definitely are not. Don’t you remember? If there is one thing we don’t need, it’s a sense of perspective!

  13. Mark

    There’s something like this on, called “The Scale of the Universe”. It’s definitely worth a look.

    There are times when I’m looking up at the Moon or stars, or looking at some really cool space pictures, and thinking to myself about what’s really going on in a very basic sense; dust clouds, rocks in orbit, et cetera. I continue to take steps away from the physics and the science and the “reality” and try to see the proverbial forest instead of the proverbial trees. Sometimes, if I do it just right, I get this amazing, overwhelming sense of perspective that literally sets my heart racing. It’s gone a moment later, and I’m left breathing heavily, wondering how the human mind can even begin to comprehend stuff like this.

    If there is anything more incredible than the sheer size of the universe, I don’t want to know about it… it might be enough to kill me.

  14. Kilted_Canuck

    I’d say the same thing for almost everything: understanding scale is essential to understanding ANYTHING

    Whether it’s history (time), geography (space), or space (whole lots of space!): scales outside of the human experience are difficult, yet very rewarding to grasp.

  15. danadam
  16. @#2: Hah! I came here intending to post that, or to see who had posted it. Didn’t take long :)

  17. @Fisilósofo, @LJAA, and @danadam,

    That’s the animation. That never gets old!

  18. citizenstx

    “Encronosate”? Someone help me out here please. Clear enough what it means, but where’d it come from?

  19. Monkey Hybrid

    @TechyDad – If you’re thinking of what I’m thinking of, then here ya go:

    And I’d have to agree with you Phil; if there’s one thing I try to put across to people, then it’s the scale of the universe. I love describing to people how big and far away our nearby neighbours are, how far away the next stars are, how long it would take to drive there in a motor car, how big our galaxy is and how many stars it contains, and then how many other galaxies there are in the known universe and the distances between them. It still makes me buzz and I like to think it gives people a better perspective of life here on earth.

    @danadam – ah, you beat me to it!

  20. AliCali

    @#7 TechyDad

    “It’s a great big Universe and we’re all really puny…”

    Do you mean that, “We’re just tiny little specks about the size of Mickey Rooney.”

  21. AliCali

    Regarding the scale, I’ve told people to turn distances or time into money. For instance, humans have been on Earth for, let’s say, 200,000 years. Dinosaurs were extinct 65 millions years ago. Some people think that’s pretty close together, and humans came about pretty quickly after dinosaurs.

    So I say, consider you’re making $200,000 per year. Now consider you’re making $65 million per year. Is that a big or little difference?

  22. doug bennion

    Scale schmale :-) Imagine the universe 10 ^ 120 years from now, or whenever, when the last protons have decayed, and the last black holes have radiated away, and all matter is twinking out of existence. As the last particles disappear, until none are left … none … scale vanishes! and the remaining space, with no points of scale-reference, can be any size you care to imagine, from itsy bitsy teeny, to infinite, to anything in between.

    That’s my story and I’m sticking to it.

  23. Tara Li

    #24 Doug – actually, there’s more than a few quantum physicists that think along the same lines. Though actually, what you have is a sea of photons, eternally being red-shifted to lower and lower energies, until at some point, maybe new big bang can occur. Beginning of the Universe – End of the Universe – it’s all brain-achingly head-messing stuff.

  24. Dragonchild

    I agree, and thanks for stating what I had such a hard time putting into words. People just have no idea. The sad thing is that the universe isn’t just misunderstood on a level of knowledge, but on one of imagination as well. Do people really understand that there are colors they can’t see, forces they can’t interact with, and places they can only experience indirectly?

    I was in an argument today about “Battlestar Galactica”, the new one. I will admit the show had genuine quality to it, from realistic special effects to some really good acting. But you know what bothered me most about it? There wasn’t a single thing about all the drama, character interactions or anything else that required it to be in SPACE. I was even more disappointed (albeit not surprised) to hear the show was EXPLICITLY designed such that everything about it could take place in an actual battleship. Um, guys? That is NOT a point in its favor; it’s proof the writers were creatively STUNTED. They had the whole GALAXY and their imaginations at their disposal. The wonders of just our solar system are mind-boggling, and they gave themselves an incomparably larger stage. So what do they make the show about? Social issues, treachery, religion, drama, President has cancer, bleh bleh BLEH. Yeesh, at least “Star Trek” had vision. For all its flaws, it pushed the envelope of its viewers’ imagination in ways that can only be explored through sci-fi.

    The universe is awesome enough without making crap up about it. How can people do that when they don’t even realize what they’re missing out on!

  25. Jeffersonian

    more than ten times the height of Mt. Everest

    It’s ten times the altitude of the summit of Mount Everest, as measured from mean sea level. But that’s not a very useful metric considering Everest is hundreds of miles inland, on top of a plateau (not looming over tidewater, like, say, Mount St Elias). Everest’s height can be measured from its Nepali base (~5300m) or its Tibetan base (~5900m).

  26. Messier Tidy Upper

    Awe-inspiring, magnificent images.

    Thankyou Cassini team and thankyou Bad Astronomer. :-)

  27. lqd

    Completely off topic, but I figured I’d post this here, given the fact that odd clouds can be seen on Saturn and the BA loves meteorology, too.

    Anyway, as an amatuer astronomer I’m always amazed at how jaded I sometimes become regarding the sizes of things. I’ll always forget that the planet or double star or nebula that I’m viewing is incomprehensively big. Literally-it’s actually impossible to wrap the human mind around it. Or, at least my mind. But I try not to forget about things like that–simply because they’re cool, and they make astronomy so much more amazing.

  28. Thea

    In a small galaxy group somewhere in the infinite vastness of the Universe, in a galaxy that in the grand scheme of things is on the large size of galaxies, in a specific unique neighbourhood, around a very unique, original, not-average G-class yellow dwarf star, orbits a pale blue dot. It may seem huge to us, but in the grand scale of things, the Earth is not very big at all.

    We do need a greater sense of scale. The Universe is the biggest thing of all, and we’ve only just scratched the surface.

  29. Messier Tidy Upper

    When it comes to the scale of things this clip :


    one are my personal favourites. :-)

    This one :

    is a classic too – even if it is a smidgin outdated. 😉

    (Mild language warning at the very end of the song.)

  30. Messier Tidy Upper

    For those who haven’t read them before here’s some of my favourite quotes on the scale of things astronomical that make you think :

    “Space isn’t remote at all. Its only an hour away if your car could go straight upwards.”
    – Page 43, Sir Fred Hoyle, ‘The Wonderful World of Space’ , Heather Couper, Octopus Books, 1980.

    (But …)

    “If it were possible to drive straight from the Earth to Neptune, taking the shortest possible route and keeping up a steady 60 m.p.h., the journey would take nearly 5,200 years.”
    – Page 57, ‘The Sky at Night’, Patrick Moore, WW. Norton & Co, 1986.

    “If we could transport Phobos and Diemos to our own Moon, they would fit comfortably inside the wide crater Copernicus with room enough for two moons of similar size.”
    – Stephen James O’Meara, page 102 “The Demon Sprites of Mars” in ‘Sky & Telescope’ magazine, June 2001.

    “To get a sense of the scale of the Jovian system, consider that if the Earth was placed at the centre of Jupiter, our Moon would lie inside the orbit of [Jupiter’s nearest large moon] Io, while distant [outer moon] Sinope would be a third of way to Mars.”
    – P. 186, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

    “Jupiter’s magnetosphere, the wasp-shaped zone within which its magnetic field takes precedence over the charged particles constituting the solar wind, extends more than seven million miles ahead of the planet in the direction of its orbital motion, … and trails so far behind that it sometimes impinges upon Saturn.”
    – P. 186, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

    “If our Earth is 1 cm from our Sun – & Pluto is 50 cm from it – then the edge of the Oort Cloud of Comet’s would be 1/2 a kilometer away!”
    – Brian Cox, ‘Wonders of the Solar System’ documentary. (Paraphrased from memory so hope I’ve got that right but pretty sure I have. Circa March 1st 2011.)

    “If you put three grains of sand inside a vast cathedral, that cathedral will be more densely packed with grains of sand than stars are found apart in space.”
    – British astronomer Sir James Jeans quoted on page 28, ‘Skywatching’, David H. Levy, Ken Fin Books, 1995.

    “Around us is a vast galaxy arrayed on scales so gigantic that galactic structure becomes discernible only once the solar system has dwindled to a dot the size of the period of this sentence.”
    – P.211, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

    “Cosmology also tells us that there are perhaps 100 billion galaxies in the universe and that each contains roughly 100 billion stars. By a curious co-incidence, 100 billion is also the approximate number of cells in a human brain.”
    – Page 237, ‘StarGazer’, Dr Fred Watson, Allen & Unwin, 2004.

    “Yet here we are with our eyes and our minds and our curiosity, six+ billion passengers aboard a tiny blue boat, bobbing and wheeling our way around one vast Catherine wheel among many.”
    – P.246, Ferris, ‘Seeing in the Dark’, Simon & Schuster, 2002.

    + Today that figure is apparently seven billion humans – less than a decade later.


    Size is, of course, relative and much depends on your point of view. (Size also depends on how fast an object is travelling as near light-speed shapes as well as masses are distorted -at least from an observers perspective – if I understand Einsteinian physics right. 8) )

  31. megan13o

    And for sure and for true, A GOD spoke to our planet of intelligent apes and said we were a MALE God’s chosen species and within that a SINGLE tribe in a desert was foremost on IT’S mind to intercede for and bless. And out of billions of options just becuase we’re self aware, we’re only ones in the whole of the universe gaining it’s attention like a tick or flea on a dog’s back.

  32. BrianDavis

    How big is NASA’s monitor cleaner budget? Because even if I had noticed Epimetheus in the first picture I would have assumed it was a speck of dirt on my screen.

  33. Messier Tidy Upper

    @19. citizenstx : “Encronosate”? Someone help me out here please. Clear enough what it means, but where’d it come from?

    Its a word game the Bad Astronomer plays and has done for years here where the word ‘enlarge’ is changed into something else related to the subject matter of the image.

    For instance, since this planet is Saturn – the Roman name for the Greek god Chronos – the BA has chosen to invent “encronosate” to replace ‘enlarge’ in this case. No, I don’t know what the BA has against the word ‘enlarge’ but clearly he wishes to avoid.

    I believe it stems from an episode of ‘The Simpsons’ where Mr Burns uses the non-word “embiggen” and when someone objects the response is generally that its “a perfectly cromulent word” – again referring to that episode. Some folks like that neologistic game here and others don’t but either way, its just one of the BA’s quirks which he’s not going to stop and something you get used to after a while here. Hope that helps. :-)

  34. At first I thought that Epimetheus was the shadow of Enceladus, but yeah, the angle is all wrong.
    Does anyone know if the shadow of a moon would be visible on Saturn’s surface (with Cassini’s cameras)?

  35. t-storm

    I drove a Saturn for years, it wasn’t that big.

  36. Or in the words of the late, great, Douglas Adams:
    Space is big. Really big. You just won’t believe how vastly hugely mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.

  37. Oops. Didn’t notice that Fan of both BA and DA and David Breece beat me to it…

  38. Brian Too

    @6. Amos Zeeberg,

    One shortcoming I find about the Powers of 10 video. The steady shifting in scale at a logarithmic rate is something that human beings cannot naturally do. So one lesson that the young or disinterested may take away is that it is possible to experience the entire universe in about 3 minutes!

    I suspect that a truer sense would be gained from experiencing a trip to a local group star, at speeds we can achieve today. As the minutes tick into hours and no noticeable progress was being made (in terms of the total time needed), I think that scale would be experienced at a human level.

    Of course this kind of thing won’t do when constant stimulation is needed to keep the audience engaged. But the likely monotony of real interstellar space travel would be an eye opener for some.

  39. Chris A.

    @MTU (#35):

    “this planet is Saturn – the Roman name for the Greek god Chronos”

    Not quite. The Greek equivalent of the Roman Saturn is Cronus (or Kronos), not Chronos. Two different entities. So, Phil should probably have written “encronusate,” not “encronosate.” But when it comes to neologisms, who’s to say what the proper spelling should be (if not he/she who coins it)?

  40. Steve B

    @35 : “Embiggen? Why, that’s a perfectly cromulent word.”

    Predictable I know, but someone had to say it …

  41. @41 Brian: I often thought it’d be cool if someone made an animation showing the view flying through the solar system at the speed of light, starting at the Sun and passing each planet (obviously, the timing of the planets’ orbits would be creatively tweaked so they’re all aligned for the flyby). Seeing as how it’d take almost 13 minutes just to get to Mars, I think that’d offer a sense of the vastness that exists even in our own interplanetary backyard.

  42. @ ^ Joseph G. : Y’know that is a superluminous idea! I second that suggestion. :-)

    I’d really love to see that put into practice even if it would take an awfully long time to get to my favourite planet – Pluto! 😉

    (Guess they could cheat just slightly and have Pluto located at its perihelion distance of just 29.6 Astronomical Units rather than its aphelion one of 49.3 AU. Mean distance of 5,900 million kilometers or 330 minutes (5.5 hours) as the photon flies. Waiting till we get to Sedna may test my patience though! 😉 )


    FWIW & if it helps :

    Planet = Travel time at light speed (Heading out from Sun in straight line.)

    Mercury = 3.2 minutes

    Venus = 6.0 minutes

    Earth =8.3 minutes (Light takes about 2 seconds travelling between Earth & Moon.)

    Mars = 13 minutes

    Ceres = ??

    Jupiter =43 minutes

    Saturn = 79 minutes

    Ouranos / 34 Tauri / Georgium Siderus = 159 minutes (2.7 hours)

    Neptune = 246 minutes (4.1 hours)

    Pluto = 330 minutes (5.5 hours)

    Eris = ???

    Haumea = ???

    Makemake = ???

    Quaoar = ???

    Sedna = ???

    NB. 1 light year = the distance travelled by light in a year = 63,240 AU or 0.30660 parsec

    1 parsec = the distance a star would have a parallax of 1 second of arc
    = 206,265 AU or 3.2616 light year

    The “pointers” to the Southern Cross are two of the brightest stars in our sky. The lower one is Alpha Centauri our nearest stellar neighbour at 4.3 light years away and a binary of yellow and orange dwarfs. The other, a blue supergiant called Hadar, Agena or Beta Centauri appears almost as bright to us but lies some 460 352 light years away! Click on my name for source link – ‘Beta Centauri Weighs In’ by Ken Croswell published 2004 November 15th.

  43. Messier Tidy Upper

    @42. Chris A. :

    @MTU (#35): “this planet is Saturn – the Roman name for the Greek god Chronos.”
    Not quite. The Greek equivalent of the Roman Saturn is Cronus (or Kronos), not Chronos. Two different entities. So, Phil should probably have written “encronusate,” not “encronosate.” But when it comes to neologisms, who’s to say what the proper spelling should be (if not he/she who coins it)?

    Fair enough – thanks. I’ll try to remember that in future. :-)

  44. Now there’s some perspective! For some reason this picture has me humming the “Galaxy Song” from Monty Python…

  45. @46 MTU: Thanks! You know, it’s not an area of my expertise, but there’s an app called Celestia that I believe would allow you to do something like this (create an automated “tour” of the solar system, traveling at the speed of light). I think new versions of Celestia even support red/blueshifting effects.
    Maybe you could create a “brief” version where the “flybys” are done at light speed, and then there’s a time counter which is accelerated in the space between planets, so you still have a sense of how long it’d actually take.

  46. Also, I’ve never heard of Georgium Siderus.

    Next time I’m pissed at someone I’ll tell ’em to cram it up Georgium Siderus. Hah.
    Yes, I’m immature. What of it? 😀


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