Mercury at perihelion

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 closest point to the Sun – its perihelion – at a distance of 0.31 AU from the Sun.

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 perihelion will be:

Object Right Ascension Declination Constellation Angular Size
Mercury 11h17m00s +05°48' Leo 7.1"
Sun 12h20m -02°15' Virgo 31'55"

The coordinates above are given in J2000.0.

From Ashburn, Mercury will be visible in the dawn sky, rising at 05:34 (EST) – 1 hour and 30 minutes before the Sun – and reaching an altitude of 12° above the eastern horizon before fading from view as dawn breaks around 06:42.

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The sky on 28 September 2016
Twilight ends
Twilight begins

27-day old moon
Waning Crescent


27 days old

Rise Culm. Set
Mercury 05:34 11:56 18:18
Venus 09:36 14:54 20:11
Moon 04:52 11:21 17:50
Mars 14:11 18:42 23:13
Jupiter 06:54 12:55 18:56
Saturn 12:26 17:18 22:10
All times shown in EDT.


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

28 Sep 2016  –  Mercury at perihelion
28 Sep 2016  –  Mercury at greatest elongation west
28 Sep 2016  –  Mercury at dichotomy
30 Sep 2016  –  Mercury reaches highest point in morning sky

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