Free Astronomy Magazine July-August 2015

JULY-AUGUST 2015 13 PLANETOLOGY acecraft 2015 will be remembered as a golden year for the exploration of the solar system, since besides the hoped but none- theless surprising reawakening in June of ESA's Philae lander on the 67P/Churyu- mov-Gerasimenko comet, we also have to record the reaching and close observation of the last two historical planetary targets that were still missing: Ceres and Pluto. Originally considered an asteroid (the first) and a planet (the latter), they both ended up in the class of dwarf planets until 2006, when the International Astronomical Union redefined the distinctive characteristics of A rtist's render- ing of the Dawn spacecraft firing its ion en- gine for manoeu- vring into orbit around Ceres. [NASA/JPL-Caltech]