Quadruple Saturn By-pass

HST Captures a View of Four of Saturn’s Many Moons

So, last entry I had you examining the details of an image of a galaxy pair some 70 or so million light-years away. Today, we’re going to look at at the details of an HST image of a scene that played out some 70 or so light-minutes away at the planet Saturn.

Four of Saturns moons transiting the planet as seen by HST. (Click to embiggen -- caution-huge image!)
Four of Saturn's moons transiting the planet as seen by HST. (Click to embiggen -- caution-huge image!)

If you click on the smaller image, you’ll get a much bigger one that shows the details of a rare transit of four of Saturn’s moons:  Titan (the large one at the top of the limb of Saturn), Mimas (below Titan and casting a shadow near the rings) and bright Dione and fainter Enceladus off to the left. These transits only happen from our point of view when Saturn’s ring plane is nearly edge-on as seen from Earth.

Later this year, on August 10 and September 4, 2009, the ring plane will appear perfectly edge-on; however, we won’t be able to see that rarity because Saturn will be too close to the Sun for good viewing. These happen periodically though — in another 14-15 years we’ll get another chance to see the rings edge-on again.

Gaze at this image (particularly the large one)  for a while — note the faint banding in Saturn’s atmosphere and the sharp shadow of Saturn’s rings darkening the cloud tops.  For more information on the image and how the HST folks got it, check out the web site news release. It’s got details about the exposures used, the observation times and much more.

There’s even a nifty video sequence of four “eclipses” as the moons transit the planet.  You can see it here.

And, thanks to Andy Chaikin for pointing out that there’s an even COOLER pic of the transits on the Hubble Heritage site. Those moons are lined up quite  nicely!

A Hubble Heritage view of the Saturn transit. (Click to embiggen.)
A Hubble Heritage view of the Saturn transit. (Click to embiggen.)


  1. Sam Marshall

    i am a year 11 student that would like to use you picture of saturn for my project if you do not reply withing 2 day i will presume that the picture is copyright free

  2. ccp

    Hi Sam,

    First, I removed the link embedded in your reply because it appeared to lead to an internet site that wants to “harvest” my password. That’s called “phishing”. If that’s not what you meant, then you need to fix that.

    Second, the image of Saturn on that entry is from Hubble Space Telescope and is in the public domain (that means NASA and the Space Telescope Science Institute have given their permission for everybody to use it in good ways). If you are really 11 years old and want to use it for a paper, go ahead, but please be professional about it (that means “grown up”) and credit the NASA/ESA Hubble Space Telescope if you do use it. That will also show your teacher that you know the right thing to do. Might help your grade.

    Third, if the picture WERE copyrighted, it remains copyrighted NO matter how long it takes me to reply to you with “permission.” Copyright doesn’t work on a basis where YOU get to say how long I have to reply to you or it belongs to you. Copyright works on the fact that someone owns the right to make copies of the picture, no matter where it appears. They get to grant you the right to make copies (i.e. use in your paper, on your web site, etc.). Everyone should ask permission to use other peoples’ work, as you have done. That is the right, proper, and legal thing to do. It’s not your place to put a time limit on it.

    Since NASA and Space Telescope Science Institute have the copyright to the picture, NASA usually gives open permissions for use of its imagery. But, they do expect you to give credit.

    Thanks for asking and thanks for reading.

Leave a Reply

Your email address will not be published.