“The Ghost of Mirach”

Hubble's backImage credit: NASA, ESA, and M. Livio (STScI). After a brief hiatus caused by an electronic failure, the Hubble space telescope is back online. And they’ve released the accompanying image to celebrate – ESA are happy too.. The next servicing mission has, however, been delayed while a new back-up system is checked. Meanwhile, also in the telescope category, comes this image [see below fold] from the Galaxy Evolution Explorer telescope – the Ghost of Mirach revealed.
Here’s the side-by-side comparison of the visible and ultra-violet light views of the “Ghost of Mirach” galaxy [central whitish spot]

"Ghost of Mirach" revealed

From the NASA press release

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.

What is this mysterious ultraviolet ring doing around an otherwise nondescript lenticular galaxy? As it turns out, previous imaging with the National Science Foundation’s Very Large Array radio telescope in New Mexico had discovered a gaseous ring of hydrogen that matches the ultraviolet ring observed by the Galaxy Evolution Explorer. The authors of this Very Large Array study attributed the gas ring to a violent collision between NGC 404 and a small neighboring galaxy 900 million years ago.

The ultraviolet observations demonstrate that, when the hydrogen from the collision settled into the plane of the lenticular galaxy, stars began to form in a ghostly ring. Young, relatively hot stars forming in stellar clusters sprinkled throughout NGC 404’s ring give off the ultraviolet light that the Galaxy Evolution Explorer was able to see.

“Before the Galaxy Evolution Explorer image, NGC 404 was thought to contain only very old and evolved red stars distributed in a smooth elliptical shape, suggesting a galaxy well into its old age and no longer evolving significantly,” said Mark Seibert of the Observatories of the Carnegie Institution of Washington in Pasadena, Calif. “Now we see it has come back to life, to grow once again.”

“The Ghost of Mirach has been lucky enough to get a new lease on life through the rejuvenating, chance merger with its dwarf companion,” added Thilker.