Mercury at aphelion

Dominic Ford, Editor
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Mercury's 88-day orbit around the Sun will carry it to its furthest point to the Sun – its aphelion – at a distance of 0.47 AU.

Unlike most of the planets, which follow almost exactly circular orbits around the Sun only varying in their distance from the Sun by a few percent, Mercury has a significantly elliptical orbit.

Its distance from the Sun varies between 0.307 AU at perihelion (closest approach to the Sun), and 0.467 AU at aphelion (furthest recess from the Sun). This variation, of over 50%, means that its surface receives over twice as much energy from the Sun at perihelion as compared to aphelion.

However, this makes little difference to Mercury's telescopic appearance, since little if any detail on its surface can be resolved by ground-based telescopes. Although its changing seasons have an incredible effect upon its surface temperatures, there is little change that is visible to amateur observers.

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

Object Right Ascension Declination Constellation Angular Size
Mercury 18h05m50s -24°32' Sagittarius 4.7"
Sun 18h34m -23°11' Sagittarius 32'31"

The coordinates above are given in J2000.0.

From Fairfield, Mercury will not be readily observable since it will be very close to the Sun, at a separation of only 6° from it.

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The sky on 30 December 2019
Twilight ends
Twilight begins

4-day old moon
Waxing Crescent


4 days old

Rise Culm. Set
Mercury 06:57 11:26 15:56
Venus 09:25 14:20 19:14
Moon 10:31 15:39 20:48
Mars 04:05 08:58 13:50
Jupiter 07:08 11:44 16:19
Saturn 08:06 12:48 17:30
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 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

28 Nov 2019  –  Mercury at greatest elongation west
10 Feb 2020  –  Mercury at greatest elongation east
11 Feb 2020  –  Mercury reaches highest point in evening sky
17 Mar 2020  –  Mercury reaches highest point in morning sky

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