A wide rings surrounds Quaoar, a dwarf planet in the outer solar system, in this artist's concept. The ring was discovered by CHEOPS, a European space telescope that is hunting for planets in other star systems. It discovered the ring by watching stars briefly disappear behind the ring as the telescope was aiming in Quaoar's direction. The ring presents a puzzle for astronomers because they expect such material to coalesce to form a moon. (Quaoar does have one known moon, Weywot, depicted at the left side of the illustration.) Quaoar is roughly 44 times farther from the Sun than Earth is, so the Sun (star at right) looks feeble. The dwarf planet is roughly 680 miles (1,100 km) in diameter. [ESA, CC BY-SA 3.0 IGO [2]]