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.
In the evening sky, Mars still holds sway as it gradually sinks into the twilight sky. Setting around midnight. The Red Planet shines at magnitude +1.7, and moves from Taurus to Gemini.
During the last few nights of May, Mars has serious competition as Mercury roars up above the horizon in the north-west. At magnitude –1.4, the innermost planet is 20 times brighter than Mars. By the end of the month it will be setting well after 10pm.
Jupiter is now rising about 11pm. The Gas Giant shines at magnitude –2.5 in Ophiuchus.
Well to the left of Jupiter you will find Saturn. Some 15 times fainter than the Gas Giant at magnitude +0.4. Rising in Sagittarius around 1am.
Outermost planet Neptune rises in the morning sky about 3am, with a dim magnitude of +7.9 in Aquarius.
Finally, you can catch brilliant Venus, very low in the east rising about 4.30am. At magnitude –3.9 it rises just before the Sun.
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; however, on either of those mornings a couple of hours before sunrise you might see around 10 meteors per hour.
Phases of the Moon for May
New Moon 4th
First Quarter 12th
Full Moon 18th
Last Quarter 26th