Night Sky Watch for May

Written by David Pugh

I hope that you are all keeping well.

Despite the cold nights we have been having lately, as we move into May the nights will be getting shorter. By the third week in the month we will actually run out of astronomical darkness, (when the Sun is more than 18 degrees below the horizon), and we will then be just in twilight conditions until late July. However, this does not mean that we cannot still observe celestial wonders, just be smarter in our observing targets, perhaps avoiding faint "fuzzies" such as faint galaxies in twilight conditions.

So, what is happening in the night sky in May? Well, for starters, for several days around May 3rd the planet Mercury will be close to the Pleiades star cluster (M45), a very rare sight low in the western sky around 9.45-10.00pm. As this will be in twilight you will need binoculars. Mercury will be at its closest to M45 on May 3rd, lying 2.2 degrees to the SE. On May 2nd it will be 4 degrees below M45 and tracks north-eastwards on successive nights so it will be 4 degrees east of M45 by the 5th.

Then by May 9th Venus joins the party lying 4.1 degrees SE of M45 at 10pm very low in the W sky but by then Mercury will be much further NE. However, Mercury steals the show again on May 13th as its small mag +0.1 disc will then lie 2.4 degrees to the upper right of a 2 day old thin crescent Moon (4% lit) low in the west during twilight.

Undoubtedly the best apparition of Mercury and Venus comes at the end of the month. On May 28th at around 10.30pm look for Venus low in the west. Only 0.5 degrees to the east of Venus you will see little Mercury with binoculars. However, Mercury will have faded dramatically to mag 2.2 by then so it will be faint in twilight. You could even try a small telescope or rich field scope with a low power eyepiece as Mercury will be only a Moon diameter away from Venus! They will still be close the following night (29th) with Mercury then 1 degree below Venus.

Mars, at mag +1.7, is still well placed in evening skies, high in the west after dusk in the constellation of Gemini but now shows a tiny disc (4") in a telescope. Mars will be only 3 degrees above a very thin crescent Moon on the evening of May 15th.

Jupiter and Saturn are both pre-dawn objects in the constellation Capricornus in the eastern sky. Uranus and Neptune are not visible this month. The night of May 5th/6th is the peak of the Eta Aquarid meteor shower, typically 30 meteors per hour under ideal conditions. However, the waning crescent Moon and low elevation of the radiant from the UK will reduce the rate seen.

During the period between last quarter and first quarter Moon (May 3rd-19th) and before we totally loose astronomical darkness you could try again for some of the galaxies in the Virgo cluster. The constellations of Virgo and Coma Berenices where they mostly lie are better placed this month, due south around 11pm. Try M64 the Black Eye Galaxy for example, if you have a telescope, or any others that I mentioned last month. You could also try the nice globular star cluster M3 not far from the bright star Arcturus. If you just have binoculars you could observe one of the very closest open star clusters to us known as the Coma Cluster or Melotte 111. It lies to the NE of second magnitude star Denebola (Beta Leonis) and contains some 40 stars of mag 5 and fainter spread over a large area (7.5 degrees). It lies only 280 lys away.

Good hunting

Best Regards

David