Sculptor galaxy. Composite image of the Sculptor spiral galaxy (NGC 253), which lies around 11 million light years from Earth, in the constellation of Sculptor. It is a starburst galaxy with very vigorous star formation and very dusty spiral arms. Image composed of data from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Southern Observatory (ESO). Low-energy X-ray radiation is red, medium energy is green and high energy is blue. Visible data from the ESO shows the backbone of the galaxy made up of stars, whilst the NuSTAR data (coloured blobs) shows a flaring source of high-energy X-rays called an ultraluminous X-ray source (ULX, blue spot, centre). This ULX is either a black hole or dense neutron star.