We have not just one, but two evening stars this month, as brilliant Venus is joined by the elusive little planet Mercury.
May is the first month when the constellation of Orion is absent from the night sky altogether, and of the prominent winter stars only Capella in Auriga the Charioteer and Castor and Pollux in Gemini remain above the western horizon. The Plough or Ursa Major (the Great Bear) is still more or less overhead with the pointers pointing to the North Star. The ‘W’ of Cassiopeia is now very low down although still easily visible in the north western sky.
It is also a good month to look for another of the circumpolar constellations; Draco the Dragon. Circumpolar constellations such as the Plough, Cassiopeia and Draco are visible all year around; this is because these stars are above the Earth in space.
Draco is represented by a stream of stars that winds its way around the North Star, so although it has no really bright stars it is still quite easy to identify. The stream starts roughly between the pointers of the Plough and the North Star, then winds its way past the Plough making off in the general direction of Cepheus.
It then turns and ends up at the ‘Dragon’s Head’, a quadrilateral of four stars near the bright star Vega, which is one of the stars that forms the Summer Triangle.
There is one notable star to mention in Draco and this is Thuban, which is not prominent in brightness and is located between Mizar, in the Plough, and the orange star Kocab, in Ursa Minor.
Use the Plough, to draw a line down following the curve of the handle to the bright orange star Arcturus in Bootes the Herdsman which is now very high up. Your downward curve will take you to Spica in Virgo the Virgin. Both Arcturus and Spica are almost due south.
High in the South West can be found Leo the Lion with its bright star Regulus, at the base of a distinctive looking ‘backwards question mark’ of stars. The small quadrilateral of stars that form Corvus the Crow is still quite conspicuous low in the south, while further to the south west and low down is the orange star Alphard, the brightest star in the constellation of Hydra the Water Snake. Alphard is often called ‘The Solitary One’ because of the lack of bright stars near it.
In the North East, two of the stars that form the summer triangle can be seen; Vega, in Lyra the Lyre, has reached a respectable altitude and Deneb in Cygnus the Swan is now becoming noticeable. The third point in the triangle, Altair in Aquila the Eagle, has yet to appear.
It is an ideal month for spotting the two closest planets to the Sun. They are located in the north west after sunset.
You can’t miss Venus. Blazing at magnitude –3.9, the evening Star sets at 9.15pm at the start of the month and at 1030pm by the months end.
Mercury lies above Venus almost all the month. At the beginning of May, the innermost planet shines at magnitude -1.0 (12 times fainter than Venus).
On the evenings of 3rd and 4th of May there is a lovely sight as Mercury passes to the left of the Pleiades star cluster, with Venus below. Fading all the time, Mercury rises high above the Evening Star until on the 12th night it drops back down. The following night the Moon is right next to Mercury. The innermost planet is at its maximum separation from the Sun on the 17th May. By the time Mercury passes just to the left of Venus on 28th of the month, it’s over 200 times fainter, at magnitude +2.2.
Mars hangs higher in the evening sky, travelling through Gemini and ending the month near the ‘twins’ Castor and Pollux. The Red planet shines at magnitude +1,6 and sets around 0.45am.
Saturn at magnitude +0.6 rises in the south east around 2am in Capricornus.
Jupiter is just behind Saturn rising at 2.30am. The gas giant has moved into Aquarius and shines at magnitude –2.3.
On the far side of Aquarius, faint Neptune with a magnitude of +7.9 rises around 3am.
Uranus is to close to the sun this month for observation.
Halley’s Comet reappears this month!. well not the actual beast, but dirt from its skirt which burns up above our heads as a shower called the Eta Aquarids. This shower, which will peak in the early hours of the mornings of May 5th and May 6th, is best seen from the southern hemisphere. This year it’s under the light of a rather wide waning crescent moon. The broad peak to this shower means that some meteors may fly for a few days before and after the predicted optimal date.
On 26th May there is the biggest and brightest full moon of 2021. The Moon will be just 357,314KM away. This Supermoon is 30% brighter than the faintest full Moon.
Phases of the Moon :-
Last Quarter 3rd
New Moon 11th
First Quarter 19th
Full Moon 26th