Free Astronomy Magazine July-August 2015

PLANETOLOGY the various categories of plan- etary bodies. By mid-July Pluto will be reached by NASA's New Horizons probe, and therefore we will talk about it in the next issue, when the initial scientific results will be avail- able. Instead, here we talk of Ceres, reached in June by the Dawn space- craft (this too a NASA’s project, with European par- ticipation) after a long journey that began on 27 Sep- tember 2007, with its launch from Cape Canaveral Air Force Station in Florida. On 15 July 2011, after a gravity assist with Mars needed for accelerating the spacecraft and shorten its trav- el time, Dawn reached its first target, the asteroid Vesta, around which it orbited for nearly 14 months, collecting information of fundamental importance on what is now considered the last of the rocky protoplanets, namely early celestial objects with a differentiated internal structure that at the dawn of the T op, the long path followed by the Dawn spacecraft to first reach Vesta, then Ceres. Left, a view of Ceres in cres- cent phase, shot on 1 March 2015 by the Framing Cameras on board the spacecraft, just before entering its first orbit, from a dis-tance of about 48,000 km. [NASA/ JPL-Caltech/UCLA/ MPS/DLR/IDA] solar system gradually formed the planets by aggregating themselves in large quan- tities under the gravitational force. After Ceres, Vesta is the second most mas- sive object in the main asteroid belt, as well as the third by volume (after the same Ceres and Pallas), and, dur- ing the most favour- able oppositions, un- der dark, cloudless skies it is also the only one that can be seen with relative ease by the naked eye. After leaving Vesta on 4 September 2012, Dawn travelled the