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Venus at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

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The sky at

Venus will reach half phase in its 2011–2012 evening apparition. It will be shining brightly at mag -4.4.

From Fairfield , this apparition will be exceptionally well placed and prominent, reaching a peak altitude of 44° above the horizon at sunset on 28 Mar 2012.

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 Venus will appear at sunset over the course of the apparition. All times are given in Fairfield local time.

Date Sun
sets at
sets at
at sunset
at sunset
29 Dec 201116:2515:0522°south-west
08 Jan 201216:4119:3526°south-west
18 Jan 201216:5219:5829°south-west
28 Jan 201217:0420:2133°south-west
07 Feb 201217:1620:4336°south-west
17 Feb 201217:2921:0439°south-west
27 Feb 201217:4121:2441°south-west
08 Mar 201217:5221:4342°west
18 Mar 201219:0323:0244°west
28 Mar 201219:1423:1744°west
07 Apr 201219:2523:2944°west
17 Apr 201219:3523:3441°west
27 Apr 201219:4623:2938°west
07 May 201219:5623:1032°west
17 May 201220:0622:3224°west
27 May 201220:1521:3212°north-west

A graph of the phase of Venus is available here.

Observing Venus

The 2011–2012 evening apparition of Venus
26 Mar 2012 – Venus at greatest elongation east
28 Mar 2012 – Venus reaches highest point in evening sky
29 Mar 2012 – Venus at dichotomy
30 Apr 2012 – Venus at greatest brightness

Venus'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 a few months each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. These apparitions repeat roughly once every 1.6 years.

On these occasions, Venus is so bright and conspicuous that it becomes the third brightest object in the sky after the Sun and Moon. It is often called the morning star or the evening star.

Venus's phase

Venus'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.

Venus 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 Venus's orbit is not quite perfectly aligned with the ecliptic.

Venus's position

The coordinates of Venus when it reaches dichotomy will be:

Object Right Ascension Declination Constellation Angular Size
Venus 03h26m10s +22°08' Aries 24.1"
Sun 00h32m +03°30' Pisces 32'02"

The coordinates above are given in J2000.0.

The sky on 29 March 2012
Twilight ends
Twilight begins

7-day old moon
Waxing Crescent


7 days old

Rise Culm. Set
Mercury 06:02 12:04 18:05
Venus 08:24 15:52 23:19
Moon 10:56 18:20 00:56
Mars 16:05 22:54 05:48
Jupiter 08:09 15:05 22:02
Saturn 20:32 02:11 07:46
All times shown in EDT.


The circumstances of this event were computed using the DE405 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

29 Mar 2012  –  Venus at dichotomy
30 Apr 2012  –  Venus at greatest brightness
05 Jun 2012  –  Venus at inferior solar conjunction
05 Jun 2012  –  Transit of Venus

Image credit

None available.




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