© 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 Jan–Feb 1974 evening apparition. It will be shining brightly at mag -0.6.

From Fairfield , this apparition will be well placed but tricky to observe, reaching a peak altitude of 15° above the horizon at sunset on 11 Feb 1974.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

Jan–Feb 1974 evening apparition of Mercury

09 Jan 1974 – Mercury at superior solar conjunction
09 Feb 1974 – Mercury at greatest elongation east
09 Feb 1974 – Mercury at dichotomy
10 Feb 1974 – Mercury at highest altitude in evening sky
24 Feb 1974 – Mercury at inferior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

08 Aug 1973 – Morning apparition
18 Oct 1973 – Evening apparition
27 Nov 1973 – Morning apparition
09 Feb 1974 – Evening apparition
23 Mar 1974 – Morning apparition
04 Jun 1974 – Evening apparition
22 Jul 1974 – 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 22h41m50s 7°21'S Aquarius 7.2"
Sun 21h33m 14°29'S Capricornus 32'25"

The coordinates above are given in J2000.0.

The sky on 24 Nov 2024

The sky on 24 November 2024
Sunrise
06:49
Sunset
16:27
Twilight ends
18:04
Twilight begins
05:12

23-day old moon
Waning Crescent

30%

23 days old

Planets
Rise Culm. Set
Mercury 08:34 13:01 17:28
Venus 10:14 14:42 19:09
Moon 00:22 06:55 13:17
Mars 20:46 04:08 11:31
Jupiter 17:18 00:45 08:11
Saturn 13:01 18:33 00:05
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

09 Feb 1974  –  Mercury at greatest elongation east
10 Feb 1974  –  Mercury at highest altitude in evening sky
15 Mar 1974  –  Mercury at highest altitude in morning sky
23 Mar 1974  –  Mercury at greatest elongation west

Image credit

© NASA/JPL/MESSENGER

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Fairfield

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41.14°N
73.26°W
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