The night sky in May 2016

posted 27 Apr 2016, 12:37 by Pete Collins
by Anne Holt

Sunset:  1 May   20-40      31 May  21-27

New moon:  6 May   Full moon:  21 May

 This month's highlight is, of course, the transit of Mercury on 9th. Between 12-12 and 19-42 the planet will pass directly between the Earth and the Sun and will be visible, through specially adapted telescopes, as a tiny black dot moving across the sun's disc. This is quite a rare occurence, the last time it happened was in November 2006. If you would like to know more about it, and, if the weather is favourable, see it for yourself, come along to our open day an Heaton Park Farm Centre (behind the Stables Cafe).  We'll have solar scopes set up outside and an information display in the classroom all afternoon and early evening.


As the sky darkens at the start of the month Lyra and Cygnus are rising in the north east, followed a couple of hours later by Aquila.  In the later part of the night the Summer Triangle formed by Vega, Deneb and Altair, the brightest star in each of these three constellations, should be easily visible. By the end of the month Aquila will be above the horizon by around 11pm. The brightest part of the Milky Way visible to us in the UK runs through the Summer Triangle and down through Scutum and Sagittarius.

The Plough is still very high in the sky for most of the night, standing on its handle, so Cassiopeia, the W shaped 'Lady in the Chair',  on the opposite side of the Pole Star is very low down in the north.

Bootes, the herdsman, is now riding high although only Arcturus, the brightest star in the celestial northern hemisphere, is above magnitude 2, so its kite asterism may not be easily visible in our light polluted skies. Arcturus is easy to find though - just follow the arc of the Plough's handle down to the south until you come to Arcturus.  Carry on the arc a bit further and you come to the star Spica, the brightest star in Virgo.

At this time of year when you look up to the south you are looking out of the plane of our Milky Way galaxy instead of along it like you do in winter and summer, so there aren't many bright stars, open star clusters and nebulae. However, if you've got a telescope this is a good time of year to hunt down globular clusters like M13, the Great Globular Cluster in Hercules, and faint galaxies like the many galaxies lying in the bowl of Virgo and into Coma Berenices.


Mercury: Too close to the sun to be visible, this month - except on 9th of course, when, clouds permitting, we will see it traversing the face of the Sun.

Venus: Might just be visible in the first few days of May, when it rises about ten minutes before the sun.

Mars: In Scorpio, mag - 1.5. Rising just before midnight at the start of the month, when it will be just above Antares, whose name means 'rival of Mars'.  At the moment though, it's no contest as the planet far outshines the mag 1.1 red giant. The planet's movement is still westwards (retrograde) against the background stars. On 21st at 11pm it is 5 degrees south of the full moon. It reaches opposition on 22nd and on 30th is at its closest to Earth - actually the closest it has been since 2005.  By this time it will have moved into Libra and be rising at around 8pm.  It will also have brightened to mag -2.1, rivalling Jupiter, though with a noticeably redder hue. It is still very low in the sky, unfortunately, but well worth observing through a telescope from a site with a clear southern horizon, as the disc appears quite large so plenty of detail should be visible.

Jupiter:  in Leo,  mag -2.3. Still very prominent as darkness falls. Setting by 4am in early May and around 2am at the end of the month. By this time it will have faded slightly to mag -2. It is currently retrograde but returns to direct (prograde) motion on 10th.

Saturn:  in Ophiuchus, mag 0.1. Rising well before midnight in early May and by about 9-30pm at month end. Still very low in the Southern sky but, as with Mars, well worth seeing through a scope, especially in the last few days of the month. As it nears opposition the rings appear much brighter, this is because the sun shines directly on to the planet, from our perspective, so the shadows cast by the individual ring bodies wil be directly behind them, hidden from view rather than being visible and cutting out some of the light.  This is known as the Seeliger effect, after Hugo von Seeliger who first explained the phenomenon in 1887.

Uranus:  not visible this month

Neptune:  in Aquarius. Rising not long before the Sun, so unlikely to be visible in the pre-dawn glare.

Meteor Showers

There are a few minor meteor showers this month.

The Eta Aquarids, active between April 19th and May 28th, dust particles originating from Halley's comet, are best seen from the Southern hemisphere, as the radiant is below the horizon from our latitude. However, we could still get a ZHR of arouind 10 at the peak on 5th/6th, best seen between 3am and dawn. These are fast moving meteors, often leaving persisient trails.  The shower could include 'Earthgrazers' - bright, long lasting meteors travelling horizontally across the sky, just before dawn.

May Camelopardids:  A fairly new shower originating from comet 209P/Linear.  This was originally predicted to be a fairly active shower but doesn't appear to have lived up to expectations.  It might be worth having a look on 24th, just in case they do put on a show this year.

Spring Antehelion Source:  Several very minor showers with radiants along the ecliptic, directly opposite the position of the sun - is active in early and late May..