Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed


Objects: Mercury

Mercury will reach half phase in its Aug–Sep 2001 evening apparition. It will be shining brightly at mag 0.1.

From Fairfield , this apparition will not be one of the most prominent and very difficult to observe, reaching a peak altitude of 8° above the horizon at sunset on 8 Sep 2001.

Aug–Sep 2001 evening apparition of Mercury

07 Sep 2001 – Mercury at highest altitude in evening sky
18 Sep 2001 – Mercury at greatest elongation east
23 Sep 2001 – Mercury at dichotomy
13 Oct 2001 – Mercury at inferior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

10 Mar 2001 – Morning apparition
22 May 2001 – Evening apparition
09 Jul 2001 – Morning apparition
18 Sep 2001 – Evening apparition
29 Oct 2001 – Morning apparition
11 Jan 2002 – Evening apparition
21 Feb 2002 – 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 13h32m10s 13°03'S Virgo 7.5"
Sun 12h01m 0°06'S Virgo 31'52"

The coordinates above are given in J2000.0.

The sky on 22 Nov 2024

The sky on 22 November 2024
Sunrise
06:47
Sunset
16:28
Twilight ends
18:05
Twilight begins
05:10


Waning Crescent

48%

21 days old

Planets
Rise Culm. Set
Mercury 08:40 13:06 17:32
Venus 10:13 14:39 19:06
Moon 22:16 05:32 12:36
Mars 20:52 04:15 11:38
Jupiter 17:26 00:53 08:20
Saturn 13:09 18:41 00:13
All times shown in EST.

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

18 Sep 2001  –  Mercury at greatest elongation east
29 Oct 2001  –  Mercury at highest altitude in morning sky
29 Oct 2001  –  Mercury at greatest elongation west
11 Jan 2002  –  Mercury at greatest elongation east

Image credit

© NASA/JPL/MESSENGER

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