The planet Venus will be approaching the Pleiades open cluster at the start of April, making for a beautiful sight that will be visible with the naked eye, through binoculars and a telescope.
Venus has dominated the western twilight sky for many weeks and is now a familiar sight after sunset. The planet is very bright, shining at mag –4.3 on 1 April, brightening to –4.4 by the end of April.
It’s favourably positioned for UK viewing, staying above the horizon for nearly five hours on 1 April and 4.3 hours on the 30th.
Venus is easy to spot as soon as the Sun sets but this extended period above the horizon means that its visibility improves because there is time for the background sky to fully darken.
At the start of April, Venus appears against an astronomically dark sky for 2.7 hours. By the end of the month, the expanding period of daylight erodes this time to 1.7 hours.
One issue when waiting for Venus to appear against a truly dark sky is its lower altitude.
At the month’s start, Venus’s appearance is further enhanced by virtue of its position against the background stars.
Left: movement of Venus through the Pleiades in early April, with positions for 23:00 BST (22:00 UT); Right: the main stars of the Pleiades. Credit: Pete Lawrence
On 1 April, it lies 2˚ west-southwest of mag. +2.8 Alcyone (Eta (η) Tauri), the brightest star in the Pleiades open cluster.
This apparent separation is small enough to provide an excellent opportunity for astrophotography and heralds an even more spectacular conjunction between the cluster and planet over the next couple of days.
On 2 April, Venus will appear 1˚ from Alcyone. This will be a glorious sight through binoculars or a scope using a wide-field eyepiece.
Cameras with longer focal length lenses or attached to a wide-field telescope can be used to achieve additional image scale.
Venus appears against the cluster stars on 3 April, tracking one-quarter of a degree south of Alcyone.
Photography will present an interesting dilemma here. Venus is so bright that any extended exposure used in an attempt to bring out the reflection nebulosity associated with the cluster is likely to result in a blown out, over-exposed planet.
On 4 April, Venus appears east of the cluster. The main shape of the Pleiades is often described as appearing like a box with a handle.
On 4 April, the handle gets an extension thanks to the positioning of the planet. On 5 April, Venus maintains its eastern march, now appearing 1.7˚ to the east of Alcyone.
Later in April, with Venus near to the star Elnath (Beta (β) Tauri), a crescent Moon will slip by to the south of the planet. Look out for this between 25-27 April.
Pete Lawrence is an experienced astronomer and a co-presenter of The Sky at Night. This guide originally appeared in the April 2020 issue of BBC Sky at Night Magazine.