After traveling several billion miles toward the Sun, a wayward young comet-like object orbiting among the giant planets has found a temporary parking place along the way. The object has settled near a family of captured ancient asteroids, called Trojans, that are orbiting the Sun alongside Jupiter. This is the first time a comet-like object has been spotted near the Trojan population. The unexpected visitor belongs to a class of icy bodies found in space between Jupiter and Neptune. Called "Centaurs," they become active for the first time when heated as they approach the Sun, and dynamically transition into becoming...