Juno

Juno is an S-type asteroid with a diameter of 234 km, orbiting at 2.67 AU in the asteroid belt. It was one of the first four asteroids discovered and was long considered one of the 'big four' along with Ceres, Pallas, and Vesta. Juno has a relatively reflective surface (albedo 0.24) composed of iron-bearing silicates and nickel-iron, typical of stony (S-type) asteroids. Its orbit is notably eccentric (0.255), bringing it as close as 2.0 AU from the Sun and as far as 3.4 AU. Juno has an irregular, somewhat elongated shape and a large impact crater roughly 100 km across — covering a significant fraction of its surface.

At favorable oppositions, Juno reaches about magnitude 7.4, making it a straightforward target for binoculars or any small telescope. It typically ranges between magnitude 8 and 10 depending on its distance from Earth. Juno's eccentric orbit means opposition brightness varies more than for most asteroids — perihelion oppositions are considerably brighter than aphelion ones. Track its motion over two to three nights using a finder chart or planetarium software to distinguish it from background stars. Oppositions occur roughly every 15.5 months.

Juno was discovered on September 1, 1804 by German astronomer Karl Ludwig Harding at the Lilienthal Observatory near Bremen. It was the third asteroid discovered, following Ceres and Pallas. Named after the Roman queen of the gods and wife of Jupiter, Juno was considered a major planet for several decades before the growing number of asteroid discoveries led to the creation of a new 'minor planet' category. Juno was the first asteroid for which an occultation of a star was observed, in 1958, providing early constraints on its size and shape.