Asteroid 7 Iris at opposition
2013 Aug 16
Asteroid 7 Iris will be well placed for observation, lying in the constellation Aquarius, well above the horizon for much of the night.
Regardless of your location on the Earth, Iris will reach its highest point in the sky at around midnight local time.
This optimal positioning occurs when it makes its closest approach to the point in the sky directly opposite to the Sun – an event termed opposition, the exact moment of which will be 15:41 UTC. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.
At around the same time that Iris passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest in the night sky. This happens because when Iris lies opposite to the Sun in the night sky, the Solar System is lined up so that Iris, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as Iris.