Hubble: New galaxy defies conventions

WASHINGTON, Jan. 25 (UPI) -- The majority of galaxies have some level of symmetry to them. Many are spirals, like the Milky Way.

But some 25 percent look like a toddler's finger painting -- unbalanced, seemingly sporadic in their organization. They're called irregular galaxies, and their unpredictable appearance sometimes makes them hard to identify.

Recently, astronomers realized an object they thought was a planetary nebula was actually a galaxy -- an irregular one.

What had originally appeared as a cloud of gas and dust expelled by a dying star turned out to be a messy collection of stars.

NGC 5408 was first spotted in June of 1834 by astronomer John Herschel. Nearly 200 years later, the object is being reclassified. The newly identified galaxy is positioned in the constellation of Centaurus, some 16 million light-years from Earth.

Making it even more unusual is its apparent association with NGC 5408, an ultraluminous X-ray source. Astronomers believe the large amount of X-rays emanating from NGC 5408 are produced by an intermediate-mass black hole. The theoretical black hole is not as powerful as a supermassive black hole, but is much brighter than a black hole formed by the implosion of a dying star.

Researchers believe intermediate-mass black holes may help explain the evolution of the supermassive black holes found at the center of most galaxies.