Asteroid 2 Pallas at opposition

2017 Oct 23

Dominic Ford – originally published on

Asteroid 2 Pallas will be well placed for observation, lying in the constellation Eridanus, well above the horizon for much of the night.

Regardless of your location on the Earth, 2 Pallas 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 15° 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 2 Pallas 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 2 Pallas lies opposite to the Sun in the night sky, the solar system is lined up so that 2 Pallas, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 2 Pallas.

On this occasion, 2 Pallas will pass within 1.699 AU of us, reaching a peak brightness of magnitude 7.3. Nonetheless, even at its brightest, 2 Pallas 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.

Finding 2 Pallas

The star charts below mark the path of 2 Pallas across the sky around the time of its opposition.

This star chart is also available as a PDF download, or in a light-on-dark color scheme (large image, small image or PDF download).

The exact position of 2 Pallas at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 2 Pallas 03h10m30s -22°44' Eridanus 7.3

The coordinates above are given in J2000.0.

The details of this observing event were provided courtesy of