© 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 2019 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 17° above the horizon at sunset on 25 Feb 2019.

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

The table below lists how high Mercury will appear at sunset over the course of the apparition. All times are given in Fairfield local time.

Date Sun
sets at
Mercury
sets at
Altitude
at sunset
Direction
at sunset
10 Feb 201917:2018:03south-west
13 Feb 201917:2418:2010°south-west
16 Feb 201917:2718:3612°west
19 Feb 201917:3118:5114°west
22 Feb 201917:3519:0316°west
25 Feb 201917:3819:1117°west
28 Feb 201917:4219:1516°west
03 Mar 201917:4519:1216°west
06 Mar 201917:4919:0213°west
09 Mar 201917:5218:44west

A graph of the phase of Mercury is available here.

Observing Mercury

The 2019 evening apparition of Mercury
29 Jan 2019 – Mercury at superior solar conjunction
26 Feb 2019 – Mercury at dichotomy
26 Feb 2019 – Mercury at greatest elongation east
27 Feb 2019 – Mercury reaches highest point in evening sky

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 hours, 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 23h41m30s -00°28' Pisces 7.1"
Sun 22h36m -08°45' Aquarius 32'18"

The coordinates above are given in J2000.0.

The sky on 26 February 2019
Sunrise
06:32
Sunset
17:39
Twilight ends
19:11
Twilight begins
05:00

22-day old moon
Waning Crescent

48%

22 days old

Planets
Rise Culm. Set
Mercury 07:09 13:10 19:12
Venus 04:31 09:21 14:10
Moon 00:53 05:53 10:53
Mars 08:54 15:50 22:47
Jupiter 02:13 06:52 11:30
Saturn 04:03 08:44 13:25
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

26 Feb 2019  –  Mercury at dichotomy
26 Feb 2019  –  Mercury at greatest elongation east
27 Feb 2019  –  Mercury reaches highest point in evening sky
14 Mar 2019  –  Mercury at inferior solar conjunction

Image credit

© NASA/JPL/MESSENGER

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