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Fraser
2006-Apr-07, 11:06 PM
SUMMARY: A new blue ring has been discovered circling Uranus, similar to Saturn's outermost ring. The discovery was made by combining visible-light images from Hubble with near-infrared photos from the Keck Telescope in Hawaii. Around Saturn, the blue ring is caused by micrometeorite impacts with Enceladus. This causes a fine mist of tiny particles that scatter and reflect mostly blue light. A similar situation could be happening at Uranus.

View full article (http://www.universetoday.com/am/publish/blue_ring_ur.html)
What do you think about this story? post your comments below.

Mild mannered
2006-Apr-10, 10:18 AM
Cool
This article gave me another thought I thought I'd ask about - specifically the blue ring

If a planet or any other body emitted a sufficient amount of radiation or was surrounded by a gas or other medium of sufficient density might we not see a similar blue ring phenonema caused by charge particles hitting / passing through this medium - as in Cherenkov radiation?
"Cherenkov (sometimes spelled ) radiation is emitted whenever charged particles pass through matter with a velocity v exceeding the velocity of light in the medium, "
Not suggesting this is the case here but with other more exotic objects out there

Jerry
2006-Apr-10, 03:25 PM
"We know now that there is at least one way to make a blue ring that doesn't involve plumes, because Mab is surely too small to be internally active," said Showalter

Not!

Most astrophysicists consider Enceladus to small and light to produce the heat necessary to create the plumes. Since the heating mechanism causing the plumes on Enceladus is not well understood, it is not reasonable to assume a seperate mechansim is required to create the sub-micron scale particles. Simple is usually better, and assuming the particles are ejected from Eceladus is a reasonable explanation. It is not reasonable to assume there is no similar mechanism creating the blue ring of uranus simply because Mab is 'surely too light and too small'. Bad inferential science!

George
2006-Apr-10, 03:49 PM
Are you suggesting Mab may produce plumes (since we do not have enough understanding of plume mechanisms)?

Do we even know the ring is actually blue in color? Has it been imaged as blue? It seems it is assigned blue because of the lack of red (IR).

Joseph A. Burns did a chapter in The New Solar System which showed where the C ring was "blue", the Cassini division was "blue" (though thin, of course), the outer edge of the division was green, and the A and B ring were red. The color used in his illustration, however, was more violet than blue, but that could be a printing issue.

[Was I wrong to start a similar thread on this in the "Astronomy" forum? After checking, I had assumed it did not make it in UT.]