3 Juno
3 Juno was the third asteroid to be discovered, on September 1, 1804 by German astronomer Karl L. Harding. It is named after the mythological figure Juno.
Juno, head of the Juno family of asteroids, is one of the largest main belt asteroids, measuring about 234 km in diameter. It is an S-type asteroid, meaning that it is highly reflective and composed of nickel-iron mixed with iron and magnesium silicates.
According to James L. Hilton (1999), Juno's orbit was observed to change (slightly) in 1839, "very likely" due to an "unmodeled encounter" — that is to say, some other object passed very close to it or actually hit it.
Juno was the first asteroid for which an occultation was observed. It passed in front of a dim star (SAO 112328) on February 19, 1958. Since then, several occultations by Juno have been observed.
Juno was recently imaged by the Hooker telescope at Mount Wilson Observatory, using adaptive optics. The study revealed that Juno has had a 100-kilometre crater blasted out of it by an ancient impact, which makes the asteroid look as though a 'bite' has been taken out of it.
