Asteroid 2 Pallas at opposition

2015 Jun 12

Dominic Ford – originally published on

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

Regardless of your location on the Earth, Pallas will reach its highest point in the sky at around midnight local time.

From London (click to change), it will be visible all night. It will become visible at around 23:30 (GMT) as the dusk sky fades, 57° above your south-eastern horizon. It will be lost to dawn twilight at around 02:23, 60° above your south-western 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 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 Pallas lies opposite to the Sun in the night sky, the solar system is lined up so that 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 Pallas.

On this occasion, Pallas will pass within 2.405 AU of us, reaching a peak brightness of magnitude 8.6. Nonetheless, even at its brightest, 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.

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

Object Right Ascension Declination Constellation Magnitude
Asteroid 2 Pallas 17h32m30s +25°32′ Hercules 8.6

The coordinates above are given in J2000.0.

The details of this observing event were provided courtesy of