Comets and asteroids
Asteroid 3 Juno reaches opposition on 2 April in the constellation of Virgo
Asteroid 3 Juno is one of the larger bodies in the asteroid belt. It reaches opposition on 2 April 2020, within the main body of Virgo. On 1 April it shines at mag. +9.6 and is located just south of the two-thirds position along a line from mag. +3.4 Heze (Zeta (z) Virginis) towards Auva (Delta (d) Virginis), which is also of mag. +3.4. It then follows a path towards Auva, performing a very close apparent pass of this star on 17 April. The asteroid remains at mag. +9.6 through opposition, two magnitudes fainter than it can achieve at perihelic oppositions – when Juno is at its closest to the Sun. As it appears to trundle through Virgo, 3 Juno will pass the mag.
+11.3 galaxy NGC 4900 on the evening of 10 April. It dims to mag. +10 on 26 April, a magnitude it then maintains until the end of the month.
Juno is the 11th largest asteroid with tri-axial ellipsoid dimensions of 320 x 267 x 200km and a mean diameter of 247km. It is the second largest stony (siliceous or S-type) asteroid, the largest being 15 Eunomia, and contains an estimated 1 per cent of the entire mass of the asteroid belt. This pales into insignificance compared to the largest object in the asteroid belt, dwarf planet Ceres, Juno’s mass being just 3 per cent that of Ceres. Juno’s elliptical orbit is highly eccentric and takes it out as far as 3.35 AU (where 1 AU is the distance between the Sun and the Earth) from the Sun at aphelion, and in as close as 1.99 AU at perihelion. The entire orbit takes 4.36 years to complete and is quite inclined, with a tilt of 12˚ to the ecliptic plane.
Analysis of Juno’s spectrum has led to a theory that this body could be the source of chondritic, or stony, meteorites. A series of images made using ALMA (Atacama Large Millimeter/submillimeter Array) have revealed a great deal of information about Juno, showing us much of a single rotation and resolving large surface features. There is evidence that the asteorid 3 Juno has a massive 100km impact crater on its surface.