This beautiful image of Comet 67P/Churyumov–Gerasimenko was taken by space probe Rosetta on August 3, 2014. 67P, like all comets, is mainly composed of water ice, dust and smaller rocky particles. When the image was taken the comet was about 405 million km or 2.7 AU away from the Sun. The Sun's radiation was not strong enough for large scale evaporation of the ice - thus the comet was still inactive at this point in time. This may change during the comets approaches of its perihelion (the closest distance from the Sun), in case of 67P it was 1.24 AU in August 2015.
The comet itself has a size of 3.5 x 4 km and consists of two connected sections of different size. 67P is a short-period comet, needing just 6.45 years for a full orbit around the Sun.If interested, read more about: Asteroids, meteoroids, meteors, meteorites, comets