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.
Brilliant Venus shinning at magnitude –4.5, starts the month as the evening star, shinning all evening long, and setting after midnight. Through a telescope or good binoculars you can make out its crescent shape. But Venus quickly swings towards the Sun and disappears by the end of May.
In the second half of May Mercury joins Venus in the evening sky. Around 15th of the month you can spot Mercury to the lower right of Venus, setting about 10pm. The innermost planet moves rapidly upwards, passing to the left of Venus on 21st and 22nd May when it’s at magnitude –0.6. Mercury continues to rise higher and fade; by the months end it’s at magnitude +0.2 and setting at 11pm.
The gas giants Jupiter and Saturn rise together around 1am. Jupiter the brighter at magnitude –2.5, lies in Sagittarius. Saturn at magnitude +0.5 inhabits the neighbouring constellation Capricornus.
Mars starts the month near Saturn, also in Capricornus, but heads leftwards during the course of the month to end up in Aquarius. Shining at magnitude +0.2, the Red Planet can be seen rising just before 3am.
At magnitude +7.9, Neptune lies in Aquarius, rising around 3am. Uranus is lost in the Suns glare this month.
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 the bright moonlight spoils the show.
On 7th May there’s a supermoon. Though the full Moon is not as big and bright as it was on 8th April.
Phases of the Moon
Full Moon 7th
Last Quarter 14th
New Moon 22nd
First Quarter 30th