Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed


Objects: Mercury

Mercury will reach half phase in its May–Jun 1960 evening apparition. It will be shining brightly at mag 0.0.

From London , this apparition will be well placed but very difficult to observe, reaching a peak altitude of 13° above the horizon at sunset on 12 Jun 1960.

May–Jun 1960 evening apparition of Mercury

17 May 1960 – Mercury at superior solar conjunction
11 Jun 1960 – Mercury at highest altitude in evening sky
13 Jun 1960 – Mercury at dichotomy
19 Jun 1960 – Mercury at greatest elongation east
17 Jul 1960 – Mercury at inferior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

12 Dec 1959 – Morning apparition
23 Feb 1960 – Evening apparition
07 Apr 1960 – Morning apparition
19 Jun 1960 – Evening apparition
06 Aug 1960 – Morning apparition
15 Oct 1960 – Evening apparition
24 Nov 1960 – Morning 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 07h14m50s 23°57'N Gemini 7.2"
Sun 05h30m 23°16'N Taurus 31'29"

The coordinates above are given in J2000.0.

The sky on 23 Apr 2025

The sky on 23 April 2025
Sunrise
05:45
Sunset
20:09
Twilight ends
22:28
Twilight begins
03:28


Waning Crescent

20%

25 days old

Planets
Rise Culm. Set
Mercury 05:16 11:19 17:23
Venus 04:28 10:36 16:43
Moon 04:22 09:10 14:13
Mars 11:05 19:10 03:16
Jupiter 07:55 16:07 00:19
Saturn 04:56 10:44 16:32
All times shown in BST.

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

11 Jun 1960  –  Mercury at highest altitude in evening sky
19 Jun 1960  –  Mercury at greatest elongation east
06 Aug 1960  –  Mercury at greatest elongation west
08 Aug 1960  –  Mercury at highest altitude in morning sky

Image credit

© NASA/JPL/MESSENGER

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