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View Full Version : Hubble Sees a Rare Transit on Uranus



Fraser
2006-Sep-05, 03:21 PM
The Hubble Space Telescope recently captured a very rare event: the transit of its moon Ariel across the surface of Uranus. On Earth we call this an eclipse, when the Moon's shadow falls upon the surface of our planet. This situation is rare on Uranus; however, because the blue-green planet is tilted over on its side. The Sun, the moons and Uranus only line up once every 42 years. The last time a transit like this could have been seen was 1965, but Earth-based telescopes weren't powerful enough to image the event at the time.

Read the full blog entry (http://www.universetoday.com/2006/09/05/hubble-sees-a-rare-transit-on-uranus/)

Ray Bingham
2006-Sep-05, 08:57 PM
You refer to this event as being similar to a lunar eclipse. With the size of the small satelite would it not be more like a solar transit with the satelite appearing as just a spot crossing the sun. Has anyone calculated the apparent diameters of the satellite and the sun in relation to their distances from the "surface"? Maybe it is even more like an occultation of a star if the sun appears small enough and Ariel large enough. Of course we recognize that in the first place there may not even be a surface as we only see the shadow on the cloud tops. How long would the equinox last in relation to the orbital period of Ariel. Would we be able to see only this one passing?

Also wondering how the position of the earth during the Uranian Equinox would affect the visibility of such events. I assume the earth is somewhere near the same side of the sun as Uranus at present. Where might it have been during the 1965 Uranian Equinox or during the next one?

Assimov would would have had fun with this story.

01101001
2006-Sep-05, 09:07 PM
With the size of the small satelite would it not be more like a solar transit with the satelite appearing as just a spot crossing the sun.

I'm not even reading the article or looking up the moon's parameters. If the image has anything to do with it, that shadow is huge. Look at it. Anyone observing the sun, and in the path of that shadow, would see the sky go black for a good while. That's no mere transit.

PhantomWolf
2006-Sep-08, 01:34 AM
I think the size of the Sun from Uranus would mean it'd completely block far longer than our moon does it. By looking at the image, it'd seem to agree.

pantzov
2006-Sep-08, 04:42 AM
nothing scientific to add here. i'd just like to comment that there is a stark beauty to the photgragh. a high res version would make a nice poster or wallpaper.