The Heart Nebula lies some 7500 light years away from Earth and is located in the Perseus Arm of our Galaxy in the constellation Cassiopeia. This is an emission nebula showing glowing gas and darker dust lanes. The most obvious shape discernible is a heart, with ventricle, atrium and dividing septum. However, it is also known as The Running Dog Nebula due to its resemblance to a dog in full flight with legs hard at work underneath its body. Turn the image through 90º counterclockwise and it is more distinguishable.

The nebula is formed by plasma of ionized hydrogen and free electrons. Its intense red output and configuration are driven by the radiation emanating from a small group of stars near the nebula’s centre. This open cluster of stars, known as Melotte 15, is relatively young (around 1.5 million years) and contains a few bright stars nearly 50 times the mass of our Sun and many more dim stars that are only a fraction of our Sun’s mass. All these stars are eroding away several picturesque dust pillars with their energetic light and winds. The cluster used to contain a microquasar that was expelled millions of years ago.

The bright knotted area at the bottom right of the image is separately classified as NGC 896, also known as The Fishhead Nebula. It was the first part of this nebula to be discovered.

The Heart Nebula is immense, spanning around 260 light years and occupying an apparent area of sky sixteen times the size of the full Moon. To capture such a large area of sky this image is a two pane mosaic. Two separate sets of exposures were captured, one for the left side and one for the right. These two images were then stitched together in post-production to create the whole image that we see here.