© 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 Mar–May 2032 morning apparition. It will be shining brightly at mag 0.2.

From Cambridge , this apparition will not be one of the most prominent and very difficult to observe, reaching a peak altitude of 9° above the horizon at sunrise on 6 Apr 2032.

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Mar–May 2032 morning apparition of Mercury

16 Mar 2032 – Mercury at inferior solar conjunction
08 Apr 2032 – Mercury at highest altitude in morning sky
13 Apr 2032 – Mercury at greatest elongation west
15 Apr 2032 – Mercury at dichotomy
23 May 2032 – Mercury at superior solar conjunction

The table below lists the altitude of Mercury at sunrise over the course of the apparition. All times are given in Cambridge local time.

Date Sun
rises at
Mercury
rises at
Altitude
at sunrise
Direction
at sunrise
Mag Phase
22 Mar 203206:4106:08east3.75%
25 Mar 203206:3505:55east2.510%
28 Mar 203206:3005:45east1.816%
31 Mar 203206:2505:36east1.222%
03 Apr 203206:2005:29east0.929%
06 Apr 203206:1505:23east0.634%
09 Apr 203206:1005:18east0.440%
12 Apr 203206:0505:14east0.345%
15 Apr 203206:0005:10east0.249%
18 Apr 203205:5505:07east0.154%
21 Apr 203205:5005:04east0.158%
24 Apr 203205:4605:01east-0.062%
27 Apr 203205:4204:59east-0.167%
30 Apr 203205:3704:57east-0.271%
03 May 203205:3304:56east-0.475%
06 May 203205:2904:55east-0.580%

Mercury will brighten rapidly at the start of its morning apparition as it emerges from inferior conjunction. Prior to its apparition, it passed between the Earth and Sun, at which time it had its unilluminated side turned towards the Earth and so appeared as a thin, barely illuminated crescent. As the apparition proceeds, this crescent waxes and becomes gibbous.

Since Mercury can only ever be observed in twilight, it is particularly difficult to find when it is in a thin crescent phase. Thus, it will be significantly easier to see in the days after it reaches its highest point in the sky – when it will show a gibbous phase – than in the days beforehand.

Altitude of Mercury at sunrise

A graph of the phase of Mercury is available here.

Apparitions of Mercury

09 Nov 2031 – Evening apparition
18 Dec 2031 – Morning apparition
29 Feb 2032 – Evening apparition
13 Apr 2032 – Morning apparition
25 Jun 2032 – Evening apparition
11 Aug 2032 – Morning apparition
21 Oct 2032 – 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 23h57m00s 2°52'S Pisces 7.6"
Sun 01h35m 9°55'N Pisces 31'52"

The coordinates above are given in J2000.0.

The sky on 15 Apr 2032

The sky on 15 April 2032
Sunrise
06:00
Sunset
19:25
Twilight ends
21:07
Twilight begins
04:18

5-day old moon
Waxing Crescent

34%

5 days old

Planets
Rise Culm. Set
Mercury 05:11 11:04 16:57
Venus 05:40 11:57 18:14
Moon 10:10 17:33 00:54
Mars 07:04 14:17 21:30
Jupiter 02:31 07:16 12:00
Saturn 08:48 16:17 23:46
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

13 Apr 2032  –  Mercury at greatest elongation west
19 Jun 2032  –  Mercury at highest altitude in evening sky
25 Jun 2032  –  Mercury at greatest elongation east
11 Aug 2032  –  Mercury at greatest elongation west

Image credit

© NASA/JPL/MESSENGER

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