© 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 Nov–Dec 2197 morning apparition. It will be shining brightly at mag -0.5.

From Cambridge , this apparition will be exceptionally well placed but tricky to observe, reaching a peak altitude of 17° above the horizon at sunrise on 22 Nov 2197.

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Nov–Dec 2197 morning apparition of Mercury

05 Nov 2197 – Mercury at inferior solar conjunction
19 Nov 2197 – Mercury at dichotomy
20 Nov 2197 – Mercury at highest altitude in morning sky
21 Nov 2197 – Mercury at greatest elongation west
02 Jan 2198 – Mercury at superior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

16 Jun 2197 – Evening apparition
03 Aug 2197 – Morning apparition
13 Oct 2197 – Evening apparition
21 Nov 2197 – Morning apparition
04 Feb 2198 – Evening apparition
17 Mar 2198 – Morning apparition
29 May 2198 – 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 14h17m00s 11°10'S Virgo 7.2"
Sun 15h30m 18°57'S Libra 32'20"

The coordinates above are given in J2000.0.

The sky on 23 Nov 2024

The sky on 23 November 2024
Sunrise
06:43
Sunset
16:15
Twilight ends
17:54
Twilight begins
05:03

22-day old moon
Waning Crescent

34%

22 days old

Planets
Rise Culm. Set
Mercury 08:33 12:55 17:17
Venus 10:09 14:32 18:54
Moon 23:09 06:06 12:50
Mars 20:36 04:03 11:30
Jupiter 17:09 00:40 08:11
Saturn 12:58 18:29 23:59
All times shown in EST.

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

13 Oct 2197  –  Mercury at greatest elongation east
21 Nov 2197  –  Mercury at highest altitude in morning sky
21 Nov 2197  –  Mercury at greatest elongation west
04 Feb 2198  –  Mercury at greatest elongation east

Image credit

© NASA/JPL/MESSENGER

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