The Moon and Mercury will share the same right ascension, with the Moon passing 1°36' to the south of Mercury. The Moon will be 28 days old.
From Cambridge , the pair will be difficult to observe as they will appear no higher than 11° above the horizon. They will be visible in the dawn sky, rising at 05:18 (EST) – 1 hour and 43 minutes before the Sun – and reaching an altitude of 11° above the south-eastern horizon before fading from view as dawn breaks at around 06:31.
The Moon will be at mag -9.0, and Mercury at mag -0.2, both in the constellation Libra.
The pair will be too widely separated to fit within the field of view of a telescope, but will be visible to the naked eye or through a pair of binoculars.
A graph of the angular separation between the Moon and Mercury around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| The Moon | 15h54m20s | 19°10'S | Libra | -9.0 | 32'28"5 |
| Mercury | 15h54m20s | 17°33'S | Libra | -0.2 | 7"5 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 19° from the Sun, which is in Ophiuchus at this time of year.
The sky on 12 Dec 2031
| The sky on 12 December 2031 | ||||||||||||||||||||||||||||||||||
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1% 28 days old |
All times shown in EST.
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Source
The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
Related news
| 13 Nov 2031 | – Mercury at highest altitude in evening sky |
| 16 Dec 2031 | – Mercury at highest altitude in morning sky |
| 18 Dec 2031 | – Mercury at greatest elongation west |
| 29 Feb 2032 | – Mercury at greatest elongation east |
Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.