© NASA/Ricardo Nunes

Venus at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Venus
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Venus will reach half phase in its 2016–2017 evening apparition. It will be shining brightly at mag -4.4.

From Ashburn , this apparition will be well placed and prominent, reaching a peak altitude of 41° above the horizon at sunset on 4 Feb 2017.

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 Ashburn local time.

Date Sun
sets at
sets at
at sunset
at sunset
06 Nov 201617:0319:1017°south-west
16 Nov 201616:5419:2219°south-west
26 Nov 201616:4919:3822°south-west
06 Dec 201616:4719:5725°south-west
16 Dec 201616:4820:1728°south-west
26 Dec 201616:5320:3631°south-west
05 Jan 201717:0120:5335°south-west
15 Jan 201717:1121:0638°south-west
25 Jan 201717:2221:1640°south-west
04 Feb 201717:3421:2041°south-west
14 Feb 201717:4621:1739°south-west
24 Feb 201717:5721:0135°west
06 Mar 201718:0720:2927°west
16 Mar 201719:1720:3614°west

A graph of the phase of Venus is available here.

Observing Venus

The 2016–2017 evening apparition of Venus
12 Jan 2017 – Venus at greatest elongation east
14 Jan 2017 – Venus at dichotomy
04 Feb 2017 – Venus reaches highest point in evening sky
18 Feb 2017 – 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 22h52m00s -07°34' Aquarius 24.9"
Sun 19h44m -21°14' Sagittarius 32'31"

The coordinates above are given in J2000.0.

The sky on 14 January 2017
Twilight ends
Twilight begins

16-day old moon
Waning Gibbous


16 days old

Rise Culm. Set
Mercury 05:48 10:38 15:27
Venus 09:47 15:26 21:04
Moon 20:07 01:54 08:45
Mars 10:08 15:56 21:44
Jupiter 00:19 05:58 11:37
Saturn 05:15 10:02 14:49
All times shown in EST.


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

14 Jan 2017  –  Venus at dichotomy
04 Feb 2017  –  Venus reaches highest point in evening sky
18 Feb 2017  –  Venus at greatest brightness
20 Feb 2017  –  Venus at perihelion

Image credit

© NASA/Ricardo Nunes






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