© 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 May–Jun 2148 morning apparition. It will be shining brightly at mag 0.0.

From Cambridge , this apparition will not be one of the most prominent and very difficult to observe, reaching a peak altitude of 10° above the horizon at sunrise on 6 Jun 2148.

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May–Jun 2148 morning apparition of Mercury

01 May 2148 – Mercury at inferior solar conjunction
28 May 2148 – Mercury at greatest elongation west
03 Jun 2148 – Mercury at dichotomy
05 Jun 2148 – Mercury at highest altitude in morning sky
30 Jun 2148 – Mercury at superior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

22 Dec 2147 – Evening apparition
30 Jan 2148 – Morning apparition
11 Apr 2148 – Evening apparition
28 May 2148 – Morning apparition
09 Aug 2148 – Evening apparition
22 Sep 2148 – Morning apparition
04 Dec 2148 – 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 03h05m00s 14°07'N Aries 7.3"
Sun 04h40m 22°10'N Taurus 31'32"

The coordinates above are given in J2000.0.

The sky on 18 Apr 2024

The sky on 18 April 2024
Sunrise
05:55
Sunset
19:29
Twilight ends
21:12
Twilight begins
04:12

10-day old moon
Waxing Gibbous

82%

10 days old

Planets
Rise Culm. Set
Mercury 05:29 11:59 18:29
Venus 05:36 11:57 18:19
Moon 14:20 21:26 04:20
Mars 04:37 10:22 16:07
Jupiter 07:00 14:09 21:19
Saturn 04:27 10:03 15:39
All times shown in EDT.

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

28 May 2148  –  Mercury at greatest elongation west
05 Jun 2148  –  Mercury at highest altitude in morning sky
29 Jul 2148  –  Mercury at highest altitude in evening sky
09 Aug 2148  –  Mercury at greatest elongation east

Image credit

© NASA/JPL/MESSENGER

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Cambridge

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42.38°N
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