This is a stunning photograph of Io , one of Jupiter ’s moons. At first glance, Io looks almost unreal—its surface is splashed with bright yellows, oranges, and reds, resembling a giant pizza or a world covered in molten paint. These striking colours come from sulphur and volcanic deposits constantly reshaping its surface. Io is the innermost and third-largest of the four Galilean moons . It is slightly larger than Moon and is the fourth-largest moon in the Solar System. It is also the most volcanically active body in the Solar System, with more than 400 active volcanoes that release sulphur and sulphur dioxide. Io was discovered in 1610 by Galileo Galilei , along with the other Galilean moons: Ganymede , Callisto , and Europa . These moons are named after figures from Greek mythology associated with Zeus , whom he seduced or abducted. Io, for example, was a priestess of Hera and one of Zeus’s lovers.

This image shows the Andromeda and two satellite galaxies: Messier 32 (M32), the blue dot just above Andromeda, to the left and centre; and Messier 110 (M11), the hazy blue oval below the central spiral of Andromeda. The image was taken by NASA; JPL-Caltech University of California, Los Angeles.  Andromeda is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It is categorized at Messier 31, M31, and NGC 224. It has a diameter of 152 000 light years, and is 2.5 million light years from Earth.  Messier 32 is a dwarf "early-type" galaxy about 2 490 000 light years from the Sol Solar System. It is a satellite galaxy of the Andromeda Galaxy and was discovered by Guillaume Le Gentil in 1749. It has a radius of 330 light-years.  Messier 110 is a dwarf elliptical galaxy that is also a satellite of the Andromeda Galaxy. Charles Messier first saw the object in 1773. It was also independently discovered by Caroline Herschel in 1783, and her brother William He...