NGC 1316: After Galaxies Collide

Explanation: Astronomers turn detectives when trying to figure out the cause of startling sights like NGC 1316 . Their investigation indicates that NGC 1316 is an enormous elliptical galaxy that started, about 100 million years ago, to devour a smaller spiral galaxy neighbor, NGC 1317, just above it. Supporting evidence includes the dark dust lanes characteristic of a spiral galaxy, and faint swirls of stars and gas visible in this wide and deep image . What remains unexplained are the unusually small globular star clusters , seen as faint dots on the image . Most elliptical galaxies have more and brighter globular clusters than NGC 1316 . Yet the observed globulars are too old to have been created by the recent spiral collision . One hypothesis is that these globulars survive from an even earlier galaxy that was subsumed into NGC 1316 .