© 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 19h28m20s 23°04'S Sagittarius 5.0"
Sun 20h30m 18°58'S Capricornus 32'29"

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 2° above the horizon at dawn.

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The sky on 25 Jan 2018

The sky on 25 January 2018
Sunrise
07:20
Sunset
17:22
Twilight ends
18:55
Twilight begins
05:47

8-day old moon
Waxing Gibbous

61%

8 days old

Planets
Rise Culm. Set
Mercury 06:37 11:20 16:02
Venus 07:40 12:38 17:36
Moon 12:09 19:02 02:02
Mars 02:42 07:39 12:36
Jupiter 01:56 07:03 12:10
Saturn 05:22 10:07 14:52
All times shown in EST.

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

01 Jan 2018  –  Mercury at greatest elongation west
15 Mar 2018  –  Mercury at highest altitude in evening sky
15 Mar 2018  –  Mercury at greatest elongation east
29 Apr 2018  –  Mercury at greatest elongation west

Image credit

© NASA/JPL/MESSENGER

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Ashburn

Latitude:
Longitude:
Timezone:

39.04°N
77.49°W
EDT

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