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 23h34m40s 4°46'S Aquarius 7.9"
Sun 01h13m 7°46'N Pisces 31'55"

The coordinates above are given in J2000.0.

From Cambridge, Mercury will not be observable – it will reach its highest point in the sky during daytime and will be no higher than 2° above the horizon at dawn.

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The sky on 10 Apr 2019

The sky on 10 April 2019
Twilight ends
Twilight begins

5-day old moon
Waxing Crescent


5 days old

Rise Culm. Set
Mercury 05:20 11:06 16:51
Venus 05:05 10:46 16:27
Moon 09:34 17:12 00:54
Mars 08:15 15:47 23:19
Jupiter 00:31 05:05 09:39
Saturn 02:17 06:56 11:35
All times shown in EDT.


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

06 Apr 2019  –  Mercury at highest altitude in morning sky
11 Apr 2019  –  Mercury at greatest elongation west
18 Jun 2019  –  Mercury at highest altitude in evening sky
23 Jun 2019  –  Mercury at greatest elongation east

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