December 6, 2012
Warped Spiral Galaxy Shown In New Hubble Image
Lee Rannals for redOrbit.com - Your Universe Online
The ring structure and distorted spiral shape of NGC 922 was imaged with NASA's Chandra X-ray Observatory to reveal even more chaos in the form of ultra luminous X-ray sources.
The galaxy's unusual form is due to a cosmic bulls eye millions of years ago. A smaller galaxy, 2MASXI J0224301-244443, is located right in the heart of NGC 922, and is shooting out of the other side.
Wide-field views of the NGC 922 show the small interloper can still be seen shooting away from the scene of the crash.
As the galaxy passed through the middle of NGC 922, it set up ripples that disrupted the clouds of gas, and triggered the formation of new stars whose radiation then lit up the remaining gas.
The bright pink color of the nebula is a characteristic sign of this process, and it is caused by excited hydrogen gas.
If two galaxies are aligned just right, with the small one passing through the center of the larger one, then the ring of the nebula should help to form a perfect circle. However, more often the two galaxies are slightly off kilter, creating a circle that is noticeably brighter on one side than the other.
The objects known as collisional ring galaxies are relatively rare in our cosmic neighborhood. Although galaxy collisions and mergers are commonplace, the precise alignment and ratio of sizes necessary to form a ring like this is not.
The chances of seeing a galaxy like these nearby is low, despite the huge amount of galaxies in the Universe. NGC 922 is one of only a handful known in our cosmic neighborhood. Observations of the more distant Universe show that these rings were more common in the past.
The new image of NGC 922 consists of a series of exposures taken in visible light with Hubble's Wide Field Camera 3, and in visible and near-infrared light with the Wide Field and Planetary Camera 2.