Mercury will pass very close to the Sun in the sky as its orbit carries it between the Sun and Earth.
This occurs once in every synodic cycle of the planet (116 days), and marks the end of Mercury's apparition in the evening sky and its transition to become a morning object over the next few weeks.
At closest approach, Mercury will appear at a separation of only 1°43' from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare.
Mercury will also pass perigee – the time when it is closest to the Earth – at around the same time, since it will lie on exactly the same side of the Sun as the Earth in the Solar System. It will move to within a distance of 0.68 AU from the Earth, making it appear with its largest angular size. If it could be observed, it would measure 9.9 arcsec in diameter, whilst appearing completely unilluminated.
The exact position of Mercury at the moment it passes solar conjunction will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 12 December 2017|
24 days old
All times shown in EST.
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.
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.
|12 Dec 2017||– Mercury at inferior solar conjunction|
|27 Dec 2017||– Mercury at dichotomy|
|28 Dec 2017||– Mercury reaches highest point in morning sky|
|01 Jan 2018||– Mercury at greatest elongation west|