A Galaxy With Two Hearts
This new Hubble image shows the spiral galaxy Messier 83, otherwise known as the Southern Pinwheel Galaxy. One of the largest and closest barred spirals to us, this galaxy is dramatic and mysterious; it has hosted a large number of supernova explosions, and is thought to have a double nucleus lurking at its core.
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 (heic1110) and irregular NGC 5253 (potw1248a) 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 centre, 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, channelling 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.
However, Messier 83’s centre is mysterious and unusual; the supermassive black hole at its heart is not alone.