COMETS AND ASTEROIDS
View Asteroid 89 Julia as it reaches opposition in Aquarius, the Water Bearer
Minor planet 89 Julia reaches opposition in Aquarius this month, shining at mag. +9.0 near the Water Jar asterism. The Water Jar, or ‘Steering Wheel’, is formed of four similar brightness stars in the northern regions of Aquarius. It sits south of the triangle that forms the upside-down head of Pegasus and to the west of the faint Circlet asterism in Pisces. Its four stars are mag. +4.3 Zeta (z) Aquarii in the centre, mag. +4.4 to +4.7 variable star Pi (π) Aquarii to the north, mag. +4.0 Eta (η) Aquarii to the east and mag. +3.8 Gamma (g) Aquarii to the west. The asterism lies 5˚ east of mag. +2.9 Sadalmelik (Alpha (a) Aquarii) and is quite easy to locate.
At the start of August, 89 Julia is located a little over 1.5˚ south-southeast of Gamma Aquarii and from here tracks westnorthwest to pass one-third of a degree south of Sadalmelik on the night of 21/22 August. On 1 August, Julia shines at mag. +9.5, as mentioned above, brightening to mag. +9.0 on the 25th, when it reaches opposition. It then retains this brightness through to the month’s end. Consequently, 89 Julia may be observed with a small telescope throughout August. To confirm an observation, image or sketch the region in which you think the asteroid is lurking over the course of several nights. If you’re looking in the correct place, the asteroid’s star-like dot will appear to move.
89 Julia orbits the Sun in the main asteroid belt region between Mars and Jupiter. It’s a large object, being around 150km across. It’s a stony or siliceous asteroid (S-type) discovered in 1866 by the French astronomer Édouard Stephan and it’s named after Saint Julia of Corsica.