Sky notes from Brian Woosnam of the North Wales Astronomy Society for May 2021

The Moon phases

Last quarter 3rd. First quarter 19th. Full 26th

The planets

Jupiter can be found in the early morning southeast sky in Aquarius around 4am. At the start of the month Jupiter will rise 70 minutes before the Sun.

A waning crescent moon lies 5.9 degrees southeast of Jupiter on the morning of the 5th. By the end of the month Jupiter’s visibility will have improved and it will rise three hours before the Sun.

Saturn can also be found in the early morning southeast sky in Capricornus, a waning moon lies near Saturn on the 3rd and 4th.

Venus and Mercury are both in the evening sky Northwest in Taurus of the two mercury can been seen 30 minutes after sunset setting around 90 minutes after sunset. On the 3rd of May mercury will be 2.3 degrees south of the Pleiades open cluster M45.

On the 13th Mercury will be 2.7 degrees to the north of the waxing crescent moon and will set 135 minutes after sunset on this date. Greatest eastern elongation occurs on the 17th May and after this date mercury dims but remains visible as it re approached by the planet Venus. At Mercury's greatest elongation the solar system's innermost planet swings to a whopping 27.3 degrees west of the sun, placing Mercury in the morning sky before sunrise. That's the maximum angular separation between the sun and Mercury for all of 2021!

Venus is an evening object setting 50 minutes after the Sun on 1st May, and around 1.5 hours at the end of the month. On the evening of 12th May a very thin moon will be 2 degrees southwest of the planet which sets 70 minutes after Sun set. On the evening of the 28th May Mercury and Venus will be just 32 arcminutes apart a pair of 10x50mm binoculars will give a good view.

Mars can be found in the west in Gemini around 22.30 BST sadly the apparent size of the planet drops during May from 4.6 arc seconds on the 1st to 4.2 at the end of the month.

Events during May

Saturday 2nd Jupiter reaches an equinox, sideways on to the Sun which will be a good time to view the four largest moons. Occultation’s, transits and eclipses between the moons are possible.

Tuesday 4th Mercury will be 2.3 degrees south of the Pleiades open cluster M45 low above the northwest horizon. Look after 30 minutes after Sunset Mercury will be 6.3 degrees above and slightly left of Venus.

Thursday 6th The eta Aquarid meteor shower peaks at 4am BST. The observing window is short for the UK between 2.30BST and the morning twilight. If you have a telescope Jupiter’s moon Io will shadow eclipses Europa from 4.26 – 4.32 BST.

Wednesday 12th look to the west 30 minutes after sunset to see Venus and the very thin crescent moon which will be 2 degrees below the moon.

Thursday 13th This evening the moon, Venus and Mercury make triangle above the northwest horizon best seen 40 minutes after sunset.

Friday 14th if you have a telescope take a look at Jupiter 4.43-4.53 BST moon Ganymed shadow partially eclipses moon Io.

Saturday 15th the moon will be found 3.3 degrees of Mars this evening.

Monday 17th mercury reaches greatest eastern elongation just 2.2 degrees from the Sun in the evening sky.

Wednesday 19th if you have a telescope take a look at the moon 00.44BST to view the Clair obscure effects known as the lunar X and V. The giant floating letters start to form on the Moon’s terminator.

Sunday 23rd the bright star below and to the right of the Moon this evening is Spica.

Monday 24th the last week of the month starts the noctilucent cloud season which can be seen until early August best time 90-120 minutes after sunset low above the northwest horizon. What are noctilucent clouds? Noctilucent clouds form in the highest reaches of the atmosphere – the mesosphere – as much as 50 miles (80 km) above the Earth's surface. They're thought to be made of ice crystals that form on fine dust particles from meteors.

Wednesday 26th tonight see the brightest and largest super moon of this year.

Friday 28th look to the northwest this evening an hour after sunset Venus and Mercury will be very close.

Saturday if you have a telescope take a look at Jupiter between 3.27 – 4.17BST moon Ganymede shadow eclipse of the moon Io.

Monday 31st the planet Saturn will be 5 degrees above the waning gibbous in the morning sky.