Mercury will pass very close to the Sun in the sky as its orbit carries it around the far side of the solar system from the Earth.
This occurs once in every synodic cycle of the planet (116 days), and marks the end of Mercury's apparition in the morning sky and its transition to become an evening object over the next few weeks.
At closest approach, Mercury will appear at a separation of only 1°27' from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare.
Mercury will also pass apogee – the time when it is most distant from the Earth – at around the same time, since it will lie exactly opposite to the Earth in the Solar System. It will move to a distance of 1.45 AU from the Earth, making it appear small and very distant. If it could be observed, it would measure 4.6 arcsec in diameter, whilst appearing completely illuminated.
The position of Mercury at the moment it passes solar conjunction will be:
| Object | Right Ascension | Declination | Constellation | Angular Size |
| Mercury | 17h53m00s | 24°52'S | Sagittarius | 4.6" |
| Sun | 17h53m | 23°25'S | Sagittarius | 32'30" |
The coordinates above are given in J2000.0.
The sky on 19 Dec 2020
| The sky on 19 December 2020 | ||||||||||||||||||||||||||||||||||
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37% 5 days old |
All times shown in EST.
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Warning
Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.
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
| 10 Nov 2020 | – Mercury at greatest elongation west |
| 23 Jan 2021 | – Mercury at greatest elongation east |
| 25 Jan 2021 | – Mercury at highest altitude in evening sky |
| 26 Feb 2021 | – Mercury at highest altitude in morning sky |
Image credit
© NASA/JPL/MESSENGER