PICK OF THE MONTH
Venus
Best time to see: 30 April, from 20 minutes after sunset
Altitude: 3.5 (very low)
Location: Aries
Direction: West-northwest
Features: Phase, subtle cloud shadings Recommended equipment: Binoculars
Venus slowly re-emerges into the evening twilight during April, but being on the far side of its orbit from Earth, slow is indeed the word! On 12 April, it sits 3.7 northwest of a less than 1%-lit thin Moon which, at just 7.8 from the Sun, itself may be a tricky spot. Things improve as we head towards the end of April, Venus’s brightness helping the planet stand out so taht it can confidently be seen against the the evening twilight. Currently Venus shines at mag. –3.8.
On 25 April, Venus lies 1.1 south of mag. –1.5 Mercury, Venus setting 40 minutes after the Sun on this date. By the time the end of the month arrives, Venus sets 50 minutes after the Sun.
We had a spectacular evening apparition of Venus in 2020 when the planet was able to reach a high altitude and it was well separated from the Sun. This year’s appearance won’t be so favourable, the timing keeping Venus rather low to the horizon as it separates from the Sun. Despite this, there are still many things to look forward to.
Meetings of Venus and the waxing crescent Moon are an amazing sight to behold, and 2021 presents numerous opportunities to see these. Although the meeting of the pair on 12 April may be tricky to catch, the one on 13 May will be a little easier. The evenings of 11 and 12 June will present a fabulous opportunity to see the thin lunar crescent near Venus, dates which repeat in July. Things start getting tricky as we head into August, as Venus will be slipping further south in the sky and its time above the horizon after sunset will be short. A lovely, albeit low, meeting between the thin waxing crescent Moon and Venus occurs on the evenings of 10 and 11 August, repeated on 9 and 10 September.
Mercury
Best time to see: 30 April, from 30 minutes after sunset Altitude: 6Ō (low)
Location: Aries
Direction: West-northwest April starts with Mercury in a poor position in the morning sky. Edging closer towards the Sun, Mercury reaches superior conjunction on 19 April, marking its transition from a morning to an evening planet. Fortunately, things improve greatly for its evening appearance, Mercury rapidly increasing in elevation after sunset towards April’s end. On the 25th, the mag. –1.5 planet sits 1.2Ō northnorthwest of mag. –3.8 Venus. Both planets remain close for the rest of April. On the 30th, Mercury shines at mag. –1.1 and sets 85 minutes after the Sun.
Mars
Best time to see: 1 April, 21:00 BST (20:00 UT) Altitude: 42Ō
Location: Taurus
Direction: West
Mars is now well past its best for the current apparition, with its brightness dropping from mag. +1.3 to mag. +1.5 over the month and its apparent size dropping from and 5.3 to 4.7 arcseconds. It’s also getting lower as darkness falls; its rapid apparent eastward motion will keep it visible for a while longer but with such a small apparent disc size it’ll be tricky to get any serious detail from the planet via a scope.
A 26%-lit waxing crescent Moon sits 3.5Ō east of Mars on 17 April. On the 26th and 27th, Mars lies 0.5Ō north of the open cluster M35 in Gemini.
Jupiter
Best time to see: 30 April, from 04:30 BST (03:30 UT) Altitude: 5Ō (very low) Location: Aquarius Direction: East-southeast
Jupiter is a morning planet, rising 70 minutes before the Sun at the month’s start, but it’s poorly placed so it doesn’t achieve much of an altitude. A 22%-lit waning crescent Moon sits 5.7Ō south of Jupiter on the morning of 7 April.
At the month’s end, Jupiter still rises 70 minutes before the Sun, reaching a peak altitude of 14Ō before sunrise. Next month, Jupiter has an equinox.
Although the planet’s small axial tilt of 3.1Ō doesn’t cause dramatic seasonal variations in its atmosphere, around an equinox we do get to see some interesting mutual events between the four Galilean satellites. See page 47 for more on these.
Saturn
Best time to see: 30 April, from 04:00 BST (03:00 UT) Altitude:5Ō (low)
Location: Capricornus Direction: Southeast Saturn is a morning object, distancing itself from the Sun. It sits in the constellation of Capricornus, appearing like a mag. +0.7 yellowish star. A 31%-lit waning crescent Moon sits beneath it on the morning of the 6th, with Jupiter 12Ō to the east-northeast. At April’s end, Saturn manages to attain an altitude of around 13Ō before it’s lost in dawn twilight.
Uranus
Uranus is not visible this month, which is a pity as on 23 April it sits between mag. –3.8 Venus and mag. –1.7 Mercury. Uranus is in conjunction with the Sun on 30 April.
Neptune
Not visible this month.