The Moon and Mercury will share the same right ascension, with the Moon passing 3°15' to the south of Mercury. The Moon will be 2 days old.
From Cambridge however, the pair will not be observable – they will reach their highest point in the sky during daytime and will be no higher than 2° above the horizon at dusk.
The Moon will be at mag -9.3, and Mercury at mag 0.8, both in the constellation Leo.
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 | 09h42m00s | 8°26'N | Leo | -9.3 | 29'39"3 |
| Mercury | 09h42m00s | 11°42'N | Leo | 0.8 | 8"9 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 26° from the Sun, which is in Cancer at this time of year.
The sky on 21 Jul 2031
| The sky on 21 July 2031 | ||||||||||||||||||||||||||||||||||
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7% 2 days old |
All times shown in EDT.
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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
| 15 Jul 2031 | – Mercury at greatest elongation east |
| 29 Aug 2031 | – Mercury at greatest elongation west |
| 31 Aug 2031 | – Mercury at highest altitude in morning sky |
| 09 Nov 2031 | – 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.