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BAA Observing calendar

Mercury at superior solar conjunction

Tuesday, 2019, May 21 - 13:55

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 0°19' 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 1.32 AU from the Earth, making it appear small and very distant. If it could be observed, it would measure 5.1 arcsec in diameter, whilst appearing completely illuminated.

The exact position of Mercury at the moment it passes solar conjunction will be:

Object Right Ascension Declination Constellation Angular Size
Mercury 03h50m40s +20°27' Taurus 5.1"
Sun 03h51m +20°08' Taurus 31'36"

The coordinates above are given in J2000.0.

This entry in the observing calendar was provided by In-The-Sky.org

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