Hubble spots spiral galaxy with double nucleus at its core

Hubble has shown new image of the spiral galaxy Messier 83, otherwise known as the Southern Pinwheel Galaxy, which is thought to have a double nucleus lurking at its core.

It is one of the largest and closest barred spirals to us, and has hosted a large number of supernova explosions.

Messier 83 is not one to blend into the background. Located some 15 million light-years away in the constellation of Hydra (The Sea Serpent), it is one of the most conspicuous galaxies of its type in our skies.

It is a prominent member of a group of galaxies known as the Centaurus A/M83 Group, which also counts dusty Centaurus A and irregular NGC 5253 as members.

Spiral galaxies come in a range of types depending on their appearance and structure-for example, how tightly wound their arms are, and the characteristics of the central bulge. Messier 83 has a "bar" of stars slicing through its center, leading to its classification as a barred spiral. The Milky Way also belongs to this category.

However, Messier 83's center is mysterious and unusual; the supermassive black hole at its heart is not alone. The striking spiral displays a phenomenon known as a double nucleus-a feature that has also been spotted in the Andromeda Galaxy, the nearest spiral galaxy to us.

This does not mean that Messier 83 contains two central black holes, but that its single supermassive black hole may be ringed by a lopsided disc of stars, which orbits around the black hole and creates the appearance of a dual core.

As well as this double nucleus, Messier 83 has hosted quite a few supernova explosions-six in total that we have observed. This number is matched by only two other galaxies: Messier 61 which also has six, and NGC 6946, which tops the list with nine.