This series of images taken by Rosetta shows the development
of Coma around the nucleus of comets. As the comet moves closer to Sun, the nucleus
gets heated and this causes the ice particles to evaporate and sublimate around
the nucleus as a gas cloud. More closer it gets to sun, more evaporation
happens and the coma expands.
A sequence of images showing comet 67P/Churyumov–Gerasimenko moving against a background star field in the constellation Ophiuchus between 27 March and 4 May 2014, as the distance between the spacecraft and comet closed from around 5 million to 2 million kilometres. The comet (and Rosetta) were between 640 million km and 610 million km from the Sun during the sequence. The comet is seen to develop a dust coma as the sequence progresses, with clear activity already visible in late-April. Exposure times are 720 seconds for each image, taken with the OSIRIS Narrow Angle Camera.
Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA