Asteroid 3 Juno will reach opposition (the point at which it is directly opposite the Sun when observed from the Earth) at 7.10 pm GMT on Wednesday 7 September 2022, when it will also be at the closest point on its orbit to the Earth, 1.31 AU (i.e. 31 times as far from the Earth as the Sun, or about 195 422 000 km), and be completely illuminated by the Sun. While it is not obvious to the naked eye observer, asteroids have phases just like those of the Moon; being further from the Sun than the Earth, 3 Juno is 'full' when directly opposite the Sun. As 3 Juno is only about 247 km in diameter, it will not be visible to the naked eye, but with a maximum Apparent Magnitude (luminosity) of 7.8 at opposition, it should be visible in the Constellation of Aquarius to viewers equipped with a good pair of binoculars or small telescope, with the best visibility being at about midnight from anywhere on Earth.
Asteroid 3 Juno was discovered on 1 September 1804 by German astronomer Karl Harding, making it the third asteroid ever discovered. It was named Juno in honour of the Roman goddess Juno, wife of Jupiter. Juno is thought to be one of the 20 largest bodies in the Main Asteroid Belt, containing about 1% of all the mass in the Asteroid Belt, and is one of the two largest stony (S-type) asteroids, along with Asteroid 15 Eunomia.
3 Juno has a 1594 day (4.36 year) orbital period and an eccentric orbit tilted at an angle of 13.0° to the plane of the Solar System, which takes it from 1.98 AU from the Sun (i.e. 198% of the average distance at which the Earth orbits the Sun) to 3.36 AU from the Sun (i.e. 336% of the average distance at which the Earth orbits the Sun). As an asteroid that never comes within 1.666 AU of the Sun and has an average orbital distance less than 3.2 AU from the Sun, 3 Juno is classed as a Main Belt Asteroid.
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