Asteroid 9 Metis at opposition

2015 Sep 6

Dominic Ford – originally published on

Asteroid 9 Metis 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, Metis will reach its highest point in the sky at around midnight local time.

From London (click to change) however, it will not be readily observable since it will lie so far south that it will never rise more than 22° above the horizon.

The geometry of the alignment

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. 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 Metis 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 Metis lies opposite to the Sun in the night sky, the solar system is lined up so that Metis, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as Metis.

On this occasion, Metis will pass within 1.358 AU of us, reaching a peak brightness of magnitude 8.8. Nonetheless, even at its brightest, Metis is a faint object beyond the reach of the naked eye or binoculars; a telescope of moderate aperture and a good star chart are needed.

The exact position of Metis at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 9 Metis 23h12m30s -15°37′ Aquarius 8.8

The coordinates above are given in J2000.0.

The details of this observing event were provided courtesy of