Asteroid 3

Juno is an asteroid of irregular shape, with its longest axis measuring some 300km. Its outline is broken by a large crater roughly 100km in diameter, probably caused by a relatively recent collision. Though comparatively large for a stony asteroid, it is by no means the largest of the minor planets; Ceres, Pallas and Vesta, among others, are all considerably larger. Juno has an unusually high albedo, however, and reflects more sunlight than most asteroids. This makes it brighter than other objects of comparable size, and it was for this reason that it was among the first of the asteroids to be discovered.

Juno has an eccentric orbit that can bring it within 2 AU of the Sun at its closest approach. At this perihelion point in its orbit, the surface can warm to above the melting point of water, even exceeding 300K (approaching 30°C) at times.