© 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 Jul–Aug 2033 morning apparition. It will be shining brightly at mag -0.3.

From Fairfield , this apparition will be well placed but tricky to observe, reaching a peak altitude of 15° above the horizon at sunrise on 29 Jul 2033.

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Jul–Aug 2033 morning apparition of Mercury

04 Jul 2033 – Mercury at inferior solar conjunction
25 Jul 2033 – Mercury at greatest elongation west
28 Jul 2033 – Mercury at highest altitude in morning sky
29 Jul 2033 – Mercury at dichotomy
20 Aug 2033 – 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 Fairfield local time.

Date Sun
rises at
Mercury
rises at
Altitude
at sunrise
Direction
at sunrise
Mag Phase
14 Jul 203305:2904:43east2.610%
17 Jul 203305:3104:3010°east1.816%
20 Jul 203305:3404:2012°east1.123%
23 Jul 203305:3704:1314°east0.531%
26 Jul 203305:3904:1015°east0.140%
29 Jul 203305:4204:1115°east-0.350%
01 Aug 203305:4504:1615°east-0.660%
04 Aug 203305:4804:2514°east-0.971%
07 Aug 203305:5104:3912°east-1.181%
10 Aug 203305:5404:5510°east-1.389%
13 Aug 203305:5705:13east-1.595%

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

12 Feb 2033 – Evening apparition
26 Mar 2033 – Morning apparition
07 Jun 2033 – Evening apparition
25 Jul 2033 – Morning apparition
04 Oct 2033 – Evening apparition
13 Nov 2033 – Morning apparition
26 Jan 2034 – 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 07h11m10s 21°06'N Gemini 7.0"
Sun 08h33m 18°46'N Cancer 31'30"

The coordinates above are given in J2000.0.

The sky on 29 Jul 2033

The sky on 29 July 2033
Sunrise
05:42
Sunset
20:12
Twilight ends
22:05
Twilight begins
03:48

3-day old moon
Waxing Crescent

10%

3 days old

Planets
Rise Culm. Set
Mercury 04:13 11:36 18:58
Venus 02:50 10:15 17:41
Moon 09:05 15:26 21:41
Mars 18:07 22:18 02:28
Jupiter 21:28 02:53 08:18
Saturn 03:55 11:22 18:49
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

28 Jul 2033  –  Mercury at highest altitude in morning sky
27 Sep 2033  –  Mercury at highest altitude in evening sky
04 Oct 2033  –  Mercury at greatest elongation east
13 Nov 2033  –  Mercury at highest altitude in morning sky

Image credit

© NASA/JPL/MESSENGER

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