© NASA/JPL/MESSENGER

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

Object Right Ascension Declination Constellation Angular Size
Mercury 15h04m20s 18°32'S Libra 4.9"
Sun 14h14m 13°31'S Virgo 32'12"

The coordinates above are given in J2000.0.

From Ashburn, Mercury will not be observable – it will reach its highest point in the sky during daytime and will be no higher than 0° above the horizon at dusk.

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The sky on 29 Oct 2017

The sky on 29 October 2017
Sunrise
07:32
Sunset
18:12
Twilight ends
19:42
Twilight begins
06:02

10-day old moon
Waxing Gibbous

69%

10 days old

Planets
Rise Culm. Set
Mercury 08:42 13:42 18:42
Venus 06:05 11:48 17:32
Moon 15:18 20:46 02:19
Mars 04:53 10:54 16:55
Jupiter 07:21 12:45 18:08
Saturn 11:25 16:11 20:56
All times shown in EDT.

Warning

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.

Source

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

13 Sep 2017  –  Mercury at highest altitude in morning sky
23 Nov 2017  –  Mercury at greatest elongation east
28 Nov 2017  –  Mercury at highest altitude in evening sky
29 Dec 2017  –  Mercury at highest altitude in morning sky

Image credit

© NASA/JPL/MESSENGER

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Ashburn

Latitude:
Longitude:
Timezone:

39.04°N
77.49°W
EDT

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