The Hartley 2 comet, discovered in 1985 by British astronomer Malcolm Hartley, becomes only the fifth comet ever to have been photographed by a spacecraft.

NASA began the EPOXI mission to send a craft called Deep Impact to Hartley 2, which was 23 million miles away from earth, in late 2007. Deep Impact was able to capture some of the most detailed photos ever of the celestial phenomenon.

Hartley was photographed a few weeks after it had passed 11 million miles away from Earth, relatively close in astronomical terms.