Mercury at inferior solar conjunction

Thu, 20 Apr 2017 at01:48 EDT(276 days ago)
05:48 UTC

Dominic Ford, Editor
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The sky at

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°38' 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 0.57 AU from the Earth, making it appear with its largest angular size. If it could be observed, it would measure 11.7 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
Mercury 01h49m40s +13°02' Aries 11.7"
Sun 01h52m +11°30' Aries 31'50"

The coordinates above are given in J2000.0.

The sky on 20 April 2017
Sunrise 06:24
Sunset 19:50
Twilight ends
Twilight begins

23-day old moon
Age of Moon
23 days

All times shown in EDT.
Rise Culm. Set
Mercury 06:16 13:02 19:48
Venus 04:49 10:58 17:07
Moon 03:02 08:14 13:25
Mars 07:47 15:01 22:15
Jupiter 18:28 00:19 06:05
Saturn 00:17 05:04 09:50


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 DE405 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

01 Apr 2017, 01:52 EDT  –  Mercury at greatest elongation east
17 May 2017, 18:58 EDT  –  Mercury at greatest elongation west
29 Jul 2017, 20:24 EDT  –  Mercury at greatest elongation east
12 Sep 2017, 05:11 EDT  –  Mercury at greatest elongation west

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