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Mercury at aphelion

Dominic Ford, Editor
From the Inner Planets feed

Objects: Mercury
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The sky at

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 01h33m40s +07°11' Pisces 10.2"
Sun 02h54m +16°37' Aries 31'42"

The coordinates above are given in J2000.0.

From Seattle, Mercury will not be observable – it will reach its highest point in the sky during daytime and will be 4° below the horizon at dawn.

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The sky on 06 May 2017
Twilight ends
Twilight begins

10-day old moon
Waxing Gibbous


10 days old

Rise Culm. Set
Mercury 05:10 11:45 18:20
Venus 04:14 10:26 16:38
Moon 16:26 22:34 04:14
Mars 06:52 14:45 22:38
Jupiter 17:21 23:05 04:53
Saturn 23:35 03:58 08:17
All times shown in PDT.


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

06 May 2017  –  Mercury at aphelion
17 May 2017  –  Mercury at greatest elongation west
23 May 2017  –  Mercury at dichotomy
01 Jun 2017  –  Mercury reaches highest point in morning sky

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