Mercury at aphelion

Dominic Ford, Editor
From the Inner Planets feed

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

Object Right Ascension Declination Constellation Angular Size
Mercury 05h20m00s 20°13'N Taurus 12.2"
Sun 05h12m 22°59'N Taurus 31'30"

The coordinates above are given in J2000.0.

From San Diego, Mercury will not be readily observable since it will be very close to the Sun, at a separation of only 3° from it.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

The sky on 9 Jun 2021

The sky on 9 June 2021
Twilight ends
Twilight begins

29-day old moon
Waxing Crescent


29 days old

Rise Culm. Set
Mercury 05:57 12:55 19:53
Venus 07:01 14:12 21:22
Moon 05:02 12:15 19:33
Mars 08:36 15:38 22:41
Jupiter 00:20 05:52 11:24
Saturn 23:22 04:38 09:54
All times shown in PDT.


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.

Related news

17 May 2021  –  Mercury at greatest elongation east
04 Jul 2021  –  Mercury at greatest elongation west
09 Jul 2021  –  Mercury at highest altitude in morning sky
04 Sep 2021  –  Mercury at highest altitude in evening sky

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San Diego



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