I don't think your interpretation of the UV image is correct, Ann. If it was, then the Ghost galaxy would be vastly larger seen in UV than in visible light, and that doesn't seem to be what they're saying in the description.
I think that the galaxy really may be a lot larger in ultraviolet than in visual light, Rob.
This is what GALEX' own homepage says about Mirach's Ghost:
The first images of the Ghost of Mirach taken by the Galaxy Evolution Explorer hinted at a surrounding ultraviolet-bright extended structure. Subsequent, longer exposure observations indeed show that the lenticular galaxy is surrounded by a clumpy, never-before-seen ring of stars.
A surrounding ring must encompass an area that fits within itself. So it makes sense that the galaxy will look larger in UV light than in visual light.
There are also other galaxies which are larger in UV light than in visual light. This is well-known galaxy M 83:
The familiar visually bright disk of M 83 is the compact bright "rounded" shape at the center of both images. In the image on the right, the visual disk is surrounded by long blue "streamers" of ultraviolet-bright stars which have formed far from the bright disk. In the image on the left, the red streamers are cold gas, prime starforming material, detected by the National Science Foundation's Very Large Array in New Mexico.
Another example of a galaxy that is much larger in UV light than in visual light is NGC 4625:
NGC 4625 is the galaxy with a small bright disk and a large set of visually faint but ultraviolet-bright arms, here seen in blue.
Ann
[quote]I don't think your interpretation of the UV image is correct, Ann. If it was, then the Ghost galaxy would be vastly larger seen in UV than in visible light, and that doesn't seem to be what they're saying in the description.[/quote]
I think that the galaxy really may be a lot larger in ultraviolet than in visual light, Rob.
This is what GALEX' own homepage says about Mirach's Ghost:
[quote]The first images of the Ghost of Mirach taken by the Galaxy Evolution Explorer hinted at a surrounding ultraviolet-bright extended structure. Subsequent, longer exposure observations indeed show that [size=150][color=#8000FF][b]the lenticular galaxy is surrounded by a clumpy, never-before-seen ring of stars[/b][/color].[/quote][/size]
A surrounding ring must encompass an area that fits within itself. So it makes sense that the galaxy will look larger in UV light than in visual light.
There are also other galaxies which are larger in UV light than in visual light. This is well-known galaxy M 83:
[img]http://www.nasa.gov/images/content/222777main_b-516.jpg[/img]
The familiar visually bright disk of M 83 is the compact bright "rounded" shape at the center of both images. In the image on the right, the visual disk is surrounded by long blue "streamers" of ultraviolet-bright stars which have formed far from the bright disk. In the image on the left, the red streamers are cold gas, prime starforming material, detected by the National Science Foundation's Very Large Array in New Mexico.
Another example of a galaxy that is much larger in UV light than in visual light is NGC 4625:
[img]http://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/NGC_4625-galex-dss.jpg/300px-NGC_4625-galex-dss.jpg[/img]
NGC 4625 is the galaxy with a small bright disk and a large set of visually faint but ultraviolet-bright arms, here seen in blue.
Ann