Asteroid 29 Amphitrite at opposition

2015 Oct 25

Dominic Ford – originally published on In-The-Sky.org

Asteroid 29 Amphitrite will be well placed for observation, lying in the constellation Aries, well above the horizon for much of the night.

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

From London (click to change), it will be visible between 18:45 and 04:23. It will become accessible at around 18:45, when it rises 24° above your eastern horizon, and then reach its highest point in the sky at 00:36, 56° above your southern horizon. It will become inaccessible at around 04:23 when it sinks to 25° above your 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 Amphitrite 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 Amphitrite lies opposite to the Sun in the night sky, the solar system is lined up so that Amphitrite, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as Amphitrite.

On this occasion, Amphitrite will pass within 1.391 AU of us, reaching a peak brightness of magnitude 8.5. Nonetheless, even at its brightest, Amphitrite 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 Amphitrite at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 29 Amphitrite 01h48m30s +17°36′ Aries 8.5

The coordinates above are given in J2000.0.


The details of this observing event were provided courtesy of In-The-Sky.org

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