Asteroid 39 Laetitia at opposition

2015 Nov 7

Dominic Ford – originally published on

Asteroid 39 Laetitia will be well placed for observation, lying in the constellation Cetus, well above the horizon for much of the night.

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

From London (click to change), it will be visible between 20:43 and 03:20. It will become accessible at around 20:43, when it rises 24° above your south-eastern horizon, and then reach its highest point in the sky at 00:04, 39° above your southern horizon. It will become inaccessible at around 03:20 when it sinks to 25° 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 Laetitia 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 Laetitia lies opposite to the Sun in the night sky, the solar system is lined up so that Laetitia, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as Laetitia.

On this occasion, Laetitia will pass within 1.537 AU of us, reaching a peak brightness of magnitude 8.9. Nonetheless, even at its brightest, Laetitia 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 Laetitia at the moment of opposition will be as follows:

Object Right Ascension Declination Constellation Magnitude
Asteroid 39 Laetitia 03h07m20s +01°07′ Cetus 8.9

The coordinates above are given in J2000.0.

The details of this observing event were provided courtesy of