Where In The Universe #72
Written by Nancy Atkinson

Here's this week's image for the WITU Challenge, to test your visual knowledge of the cosmos. You know the drill: take a look at this image and see if you can determine where in the universe this image is from; give yourself extra points if you can name the spacecraft responsible for the image. We’ll provide the image today, but won’t reveal the answer until tomorrow. This gives you a chance to mull over the image and provide your answer/guess in the comment section. Please, no links or extensive explanations of what you think this is — give everyone the chance to guess.
Click here if you want to look back at all previous Where In the Universe Challenges.
UPDATE: The answer has now been posted below.

This image from the Hubble Space Telescope is a never-before-seen astronomical alignment of a moon traversing the face of Uranus, and its accompanying shadow. The white dot near the center of Uranus’ blue-green disk is the icy moon Ariel. The 700-mile-diameter satellite is casting a shadow onto the cloud tops of Uranus. To an observer on Uranus, this would appear as a solar eclipse, where the moon briefly blocks out the Sun as its shadow races across Uranus’s cloud tops.
Check back again soon for another WITU challenge!
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September 24th, 2009 at 8:03 am
I'm gonna go with Triton Transit of Neptune by HST
September 24th, 2009 at 8:06 am
… or on second thought, Ariel transits Uranus (by HST)
September 24th, 2009 at 8:07 am
Uranus and Ariel, July 26, 2006, by the Hubble Space telescope
September 24th, 2009 at 8:08 am
That's Uranus and one of its moons, shot not too long ago by Hubble.
September 24th, 2009 at 8:11 am
First time I could recognise something on "Where in the Universe" !
Ariel – Uranus – Hubble.
September 24th, 2009 at 8:18 am
The moon Ariel casting a shadow on Uranus shot by Hubble.
September 24th, 2009 at 10:30 am
It's Uranus. Note the placement of the shadow of moon and the direction of the cloud bands.
The only spacecraft that could take this photo is Hubble.
Not sure what Moon it is. Must be one of the 4 big ones based on the size of the shadow.
September 24th, 2009 at 10:32 am
My guess was Neptune, too, just from the colour. I'm so ignorant.
That said, I hope to see missions to the ice giants before I die.
September 24th, 2009 at 1:28 pm
I think it is Triton transit on Neptune….
September 24th, 2009 at 1:29 pm
Alas, looking at the other posters..seems like i am off a planet
September 24th, 2009 at 1:44 pm
This is Uranus with the white dot is the icy moon Ariel, ths shot was produced by Hubble.
September 24th, 2009 at 3:03 pm
I was thinking Neptune at first glance but am inclined to agree with the majority of the comments that it's Uranus and Ariel.
September 24th, 2009 at 4:09 pm
I was thinking Neptune initially as well, based on the color. However, I think I have to agree with the other posters, Uranus and Ariel, picture by HST.
September 24th, 2009 at 7:21 pm
HST shot of Triton transiting Neptune, flipped on its side to make it trickier. I don't think any of Uranus' moons are large enough to cast a shadow that size, and Neptune has better defined cloud bands, too.
September 25th, 2009 at 5:01 am
Uranus because of the angle of its axis. Couldn't be from Voyager 2 because it looked bland back then and the image would be clearer. Has to be Hubble. The moon? Don't know I'll have to look that up.
September 25th, 2009 at 12:31 pm
It is Matilda transit of Uranus from Hubble…………
September 25th, 2009 at 3:26 pm
It is a famous german washing powder starting with the letter A which circles around Uranus.The picture was taken at on July 26, 2006 at about 15:30 UTC by a non human being.
September 26th, 2009 at 8:16 pm
Hey, don't forget Voyager 2, the only spacecraft to visit (and image) all four of the gas giants. But I will go with the peer pressure (and with the fuzziness of the focus) and agreed that it was taken with the HST. It *IS* a reflector, you know.
September 27th, 2009 at 5:35 pm
Well, since Nancy is so late in giving the answer to this one, I still have time to chime in:
HST took this charming little photograph of the giant planet Uranus and it's moon, Ariel.
Oh no, it's Mr. Bill!