A distant galaxy spotted by the Hubble Space Telescope doesn't fall easily into the usual categories of shapes -- spiral, elliptical or irregular -- but is a beautiful sight nonetheless, astronomers say.
A dramatic image released by NASA on Christmas Eve shows the galaxy IC 335 edge on, which is why putting it into one of the usual "shape" categories is proving difficult, scientists say.
That's because the most common characteristics of a galaxy's morphology used for classifications -- the spiral arms or a central bar -- are only visible if the galaxy is seen face-on.
This galaxy, 450,000 light years across, "could be classified as an S0 type" or lenticular galaxy, NASA says.
Such "lens-shaped" galaxies represent an intermediate shape between spiral galaxies and elliptical galaxies, the space agency says.
While they possess a thin stellar disk and a central bulge, like a spiral galaxy displays, they have consumed most of their star-making fuel so their rate of star formation is quite low.
That means the stars in IC 335 are mostly older ones, similar to star populations in elliptical galaxies.
If an SO or lenticular galaxy such as IC 335 possesses spiral arms they are usually so ill-defined that the galaxies are easily mistaken for elliptical galaxies if they are seen only edge on, NASA says.
"It clearly isn't an elliptical galaxy since it looks flat, but it doesn't seem to have matter between the stars ... so the scientists involved classify it as an intermediate type between spirals and ellipticals," says Jay M. Pasachoff, professor of astronomy at Williams College in Williamstown, Massachusetts.
S0 galaxies are generally considered to be aging and fading spiral galaxies that never experienced any interactions with other galaxies, although the exact character of such galaxies is a matter of debate among astronomers.
IC 335 is location 60 million miles from earth and is part of a four-galaxy group known as the Fornax Cluster.
