Dominic Ford, Editor
From the Inner Planets feed
Venus will be well placed for observation in the dawn sky, shining brightly at mag -4.5.
From Cambridge, it will be difficult to observe as it will appear no higher than 13° above the horizon. It will rise at 04:09 (EST) – 1 hour and 37 minutes before the Sun – and reach an altitude of 13° above the eastern horizon before fading from view as dawn breaks at around 05:27.
Venus's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is very difficult to observe most of the time.
It is observable only for a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation.
On these occasions, however, 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 or evening star.
Venus's brightness depends on two factors: its closeness to the Earth, and its phase. Its 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 reaches its brightest when it is still a crescent – with less than half of its disk illuminated. This is because it is much closer to the Earth during its crescent phases than at other times.
As a result, during evening apparitions, Venus reaches maximum brightness a few days after it is at greatest separation from the Sun, which always coincides with it showing half-phase (dichotomy).
Conversely, during morning apparitions, Venus reaches maximum brightness a few days before it is at greatest separation from the Sun.
Venus in coming weeks
The key moments in this apparition of Venus are as follows:
|18 Feb 2017 10:42 EST||– Venus at greatest brightness|
|25 Mar 2017 06:12 EDT||– Venus at inferior solar conjunction|
|26 Apr 2017 14:36 EDT||– Venus at greatest brightness|
|03 Jun 2017 01:58 EDT||– Venus at greatest elongation west|
|04 Jun 2017 02:00 EDT||– Venus at dichotomy|
Over coming weeks, the distance between Venus and the Sun will decrease each night as it sinks back into the Sun's glare. The table below lists how long before sunrise Venus will rise each night; all times are given in Cambridge local time.
|Altitude of Venus
|Direction of Venus
|19 Apr 2017||05:56||04:25||15°||north-west|
|26 Apr 2017||05:45||04:09||16°||north-west|
|03 May 2017||05:35||03:55||17°||north-west|
|10 May 2017||05:27||03:42||18°||north-west|
|17 May 2017||05:19||03:31||19°||north-west|
|24 May 2017||05:14||03:20||19°||north-west|
|31 May 2017||05:09||03:09||21°||north-west|
|07 Jun 2017||05:06||03:00||22°||north-west|
|14 Jun 2017||05:05||02:51||23°||north-west|
|21 Jun 2017||05:06||02:44||25°||north-west|
|28 Jun 2017||05:08||02:38||26°||north|
A graph of the brightness of Venus is available here.
The coordinates of Venus when it reaches greatest brightness will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 26 April 2017|
29 days old
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.
|12 Jan 2017, 10:52 EST||– Venus at greatest elongation east|
|03 Jun 2017, 01:58 EDT||– Venus at greatest elongation west|
|17 Aug 2018, 03:58 EDT||– Venus at greatest elongation east|
|06 Jan 2019, 01:02 EST||– Venus at greatest elongation west|
© NASA/Ricardo Nunes