NGC 1313

A starburst galaxy, NGC 1313 has a barred spiral shape, with the arms emanating outwards in a loose twist from the ends of the bar. The galaxy lies just 15 million light-years away from the Milky Way - a mere skip on cosmological scales. The spiral arms are a hotbed of star-forming activity, with numerous young clusters of hot stars being born continuously at a staggering rate out of the dense clouds of gas and dust. Their light blasts through the surrounding gas, creating an intricately beautiful pattern of light and dark nebulosity.

NGC 1313's appearance suggests it has seen troubled times: its spiral arms look lop-sided and gas globules are spread out widely around them. Moreover, observations have revealed that its 'real' centre, around which it rotates, does not coincide with the central bar. Its rotation is therefore also off kilter.

Strangely enough NGC 1313 seems to be an isolated galaxy. It is not part of a group and has no neighbor, and it is not clear whether it may have swallowed a small companion in its past. An explanation based on the presence of the central bar also does not hold for NGC 1313: the majority of its star formation is actually taking place not in its bar but in dense gassy regions scattered around the arms. By what mechanism the gas is compressed for stars to form at this staggering rate is unknown.

Probing further into NGC 1313's insides reveals yet more mysteries. In the midst of the cosmic violence of the starburst regions lie two objects that emit large amounts of highly energetic X-rays - so called ultra-luminous X-ray sources. These might be black holes with masses of perhaps a few hundred times the mass of an ordinary star, that formed as part of a binary star system.