... almost the entire solar system. The first probes were blasted into space toward the end of the 1950s when the Cold War between the United States and the USSR wasat its height. They have explored the ... nucleus is the solid part of acomet, in the middle of the comet’shead.• The coma is the gassy atmospherethat surrounds the nucleus when the comet nears the Sun.• The tail is the long, bright ... out from the center of the galaxy. These are the Norma Arm, the Scutum-Crux Arm, the Sagittarius Arm, and the Perseus Arm. The Sunlies in a small arm called the Orion Arm, alsocalled the Local...