Astronomy Picture of the Day

Explanation: The Rosetta spacecraft captured this remarkable series of 9 frames between March 27 and May 4, as it closed from 5 million to 2 million kilometers of its target comet. Cruising along a 6.5 year orbit toward closest approach to the Sun next year, periodic comet 67P/Churyumov-Gerasimenko is seen moving past a distant background of stars in Ophiuchus and globular star cluster M107. The comet's developing coma is actually visible by the end of the sequence, extending for some 1300 km into space. Rosetta is scheduled for an early August rendezvous with the comet's nucleus. Now clearly active, the nucleus is about 4 kilometers in diameter, releasing the dusty coma as its dirty ices begin to sublimate in the sunlight. The Rosetta lander's contact with the surface of the nucleus is anticipated in November.