© NASA/JPL/MESSENGER

Mercury at perihelion

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 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 12h38m40s -02°48' Virgo 8.0"
Sun 13h38m -10°13' Virgo 32'07"

The coordinates above are given in J2000.0.

From Washington, Mercury will not be observable – it will reach its highest point in the sky during daytime and will be no higher than 9° above the horizon at dawn.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.
The sky on 19 October 2021
Sunrise
07:47
Sunset
18:55
Twilight ends
20:19
Twilight begins
06:19

13-day old moon
Waxing Gibbous

99%

13 days old

Planets
Rise Culm. Set
Mercury 06:25 12:19 18:14
Venus 11:44 16:23 21:02
Moon 18:44 00:29 06:44
Mars 07:27 13:05 18:43
Jupiter 16:02 21:18 02:33
Saturn 15:16 20:17 01:19
All times shown in MDT.

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

19 Oct 2021  –  Mercury at perihelion
23 Oct 2021  –  Mercury at dichotomy
24 Oct 2021  –  Mercury at highest altitude in morning sky
24 Oct 2021  –  Mercury at greatest elongation west

Image credit

© NASA/JPL/MESSENGER

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Washington

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Longitude:
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37.13°N
113.51°W
MDT

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