Messier 83, the Southern Pinwheel Galaxy, is one of the largest and closest barred spiral galaxies to us.  At 15 million light-years away, it is one of the most conspicuous galaxies of its type in our skies.  It's in the constellation of Hydra (The Sea Serpent) and 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.

These bars are thought to act a bit like a funnel, channeling gas inwards towards the galaxy's centre. This gas is then used to form new stars and also to feed the galaxy's central black hole, explaining why many barred spirals -- including Messier 83 -- have very active and luminous central regions.


 Hubble and Magellan composite image of Messier 83 has hosted a large number of supernova explosions and seems to have a double nucleus lurking at its core.



Hubble and Magellan composite image of Messier 83, the Southern Pinwheel Galaxy. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)Acknowledgement: William Blair (Johns Hopkins University)

Messier 83's center is unusual; the supermassive black hole at its heart is not alone, it instead has 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 (SN 1923A, SN 1945B, SN 1950B, SN 1957D, SN 1968L, and SN 1983N). This number is matched by only two other galaxies: Messier 61, which also has six, and NGC 6946, which tops the list with nine. As well as these explosions, almost 300 supernova remnants -- the older leftovers from exploded stars -- have been found within Messier 83, detected using the data that make up this image. These observations are being used to study the life cycle of stars. As well as these old remnants, some 3000 star clusters have been identified in Messier 83, some of which are very young at under 5 million years old.

This mosaic image uses observations taken by Hubble's Wide Field Camera 3. It shows the galaxy in full, with dark dust lanes, fiery red patches of gas, and bright blue patches of recent star formation speckled across the spiralling arms. Although it looks sprawling, Messier 83 is just under half of the size of the
Milky Way.

Released at the 223rd meeting of the American Astronomical Society in Washington, DC, USA.