67P/Churyumov-Gerasimenko - Rosetta
Rosetta OSIRIS-Wide Angle Camera view of Comet 67P taken during a far excursion on April 11, 2015. When this image was taken, Rosetta was located about 140 km from the comet's center, at a 90 degree phase angle, allowing the spacecraft to observe a half-lit comet.
The day side of the comet experiences intense outgassing activity, forming the bright jets of gas and dust that face sunward. The material in these jets eventually spreads out into a diffuse cloud called the coma. The presence of the coma allowed Rosetta to observe the comet's shadow.
Image Credit: ESA / Rosetta / MPS for OSIRIS Team (MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA) / Justin Cowart