Messier 100

This stunning spiral galaxy is Messier 100 in the constellation Coma Berenices, captured here by the NASA/ESA Hubble Space Telescope — not for the first time.

After Hubble was launched, the astronomers and engineers operating the telescope found that the images it returned were fuzzy, as if it were out of focus. In fact, that was exactly what was happening. Hubble’s primary mirror functions like a satellite dish; its curved surface reflects all the light falling on it to a single focal point. However, the mirror suffered from a defect known as a spherical aberration, meaning that the light striking the edges of the mirror was not travelling to the same point as the light from the centre. The result was blurry, unfocused images.

To correct this fault, a team of seven astronauts undertook the first Servicing Mission in December 1993

Credit:
NASA, ESA
https://esahubble.org/images/potw1850a/