© NASA/JPL/MESSENGER

Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Mercury
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Mercury will reach half phase in its Oct–Nov 2185 morning apparition. It will be shining brightly at mag -0.5.

From Fairfield , this apparition will be exceptionally well placed but tricky to observe, reaching a peak altitude of 17° above the horizon at sunrise on 3 Nov 2185.

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Oct–Nov 2185 morning apparition of Mercury

17 Oct 2185 – Mercury at inferior solar conjunction
31 Oct 2185 – Mercury at dichotomy
02 Nov 2185 – Mercury at highest altitude in morning sky
02 Nov 2185 – Mercury at greatest elongation west
08 Dec 2185 – Mercury at superior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

26 May 2185 – Evening apparition
13 Jul 2185 – Morning apparition
22 Sep 2185 – Evening apparition
02 Nov 2185 – Morning apparition
15 Jan 2186 – Evening apparition
25 Feb 2186 – Morning apparition
07 May 2186 – Evening apparition

Observing Mercury

Mercury's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is lost in the Sun's glare much of the time.

It is observable for only a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. These apparitions repeat roughly once every 3–4 months.

Mercury's phase

Mercury's phase varies depending on its position relative to the Earth. When it passes between the Earth and Sun, for example, the side that is turned towards the Earth is entirely unilluminated, like a new moon.

Conversely, when it lies opposite to the Earth in its orbit, passing almost behind the Sun, it appears fully illuminated, like a full moon. However, at this time it is also at its most distant from the Earth, so it is actually fainter than at other times.

Mercury shows an intermediate half phase – called dichotomy – at roughly the same moment that it appears furthest from the Sun, at greatest elongation. The exact times of the two events may differ by a few days, only because Mercury's orbit is not quite perfectly aligned with the ecliptic.

Mercury's position

The coordinates of Mercury when it reaches dichotomy will be:

Object Right Ascension Declination Constellation Angular Size
Mercury 13h09m40s 5°11'S Virgo 7.1"
Sun 14h16m 13°38'S Virgo 32'12"

The coordinates above are given in J2000.0.

The sky on 5 May 2024

The sky on 5 May 2024
Sunrise
05:43
Sunset
19:54
Twilight ends
21:43
Twilight begins
03:54

27-day old moon
Waning Crescent

7%

27 days old

Planets
Rise Culm. Set
Mercury 04:53 11:13 17:34
Venus 05:28 12:18 19:07
Moon 04:16 10:36 17:10
Mars 04:08 10:12 16:16
Jupiter 06:17 13:27 20:37
Saturn 03:32 09:11 14:50
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

22 Sep 2185  –  Mercury at greatest elongation east
02 Nov 2185  –  Mercury at highest altitude in morning sky
02 Nov 2185  –  Mercury at greatest elongation west
15 Jan 2186  –  Mercury at greatest elongation east

Image credit

© NASA/JPL/MESSENGER

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Fairfield

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41.14°N
73.26°W
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