28-04-2007 May night sky (Article 83)

[Simon Kenny]

May night sky (Article 83)

This month sees summer constellations starting to appear over the horizon. Meantime, the late spring skies are commanded by the orange Arcturus and brilliant white Spica, — heralding long days and not so dark nights ahead. Though there are galaxies to be found in just about every part of the sky, from Ireland the observable constellations of Virgo and fainter, neighbouring Coma Berenices (located between Virgo and Leo) contains many thousands of galaxies clustered only several degrees across. Most famously is the Virgo Cluster, the nearest supercluster to our own Local Group of about 20 galaxies, including our MilkyWay and the Andromeda Galaxy. Though the average distance to the Virgo Cluster is 60 million light years, there are about 16 that can be glimpsed in only 50mm optics. In larger amateur telescopes, even the finest of these ‘star cities’ does not display more significant detail. While this may sound unexciting, the fact that we mere mortals can see the nearest piece of the large-scale structure of the Universe is where the thrill truly lies. Don’t be confused with the Coma Star Cluster, which can be seen with the unaided eye. This large, loose cluster of stars represents the shorn locks of the Egyptian Queen, Berenice. Placed in the sky by the gods after she cut off her long hair upon their granting her wish to have her husband (Ptolemy III, Euergetes) return safely from war with the Assyrians. Once regarded as the tuft of Leo’s tail, or a pond, Berenice’s enchanting myth holds sway today. The three brightest stars of this constellation form a small right triangle. Coma Berenices contains our north galactic pole, hence we are looking perpendicular to the plane of our MilkyWay Galaxy, to the domain beyond our Galaxy. External galaxies are easier to see in these regions, since the star-glow and dust of our own home galaxy does not obscure them.

Venus remains absolutely stunning this month in NW, but not yet at its brightest for 2007. However, best viewing is this month as the brightening skies will catch up, thus its brilliance against a dark sky will soon diminish. Saturn remains a late evening object, while Jupiter rises now in SE long before midnight. You may also glimpse Mercury hugging the SW horizon later in the month.
(Warning: do not use a telescope or binoculars with the Sun above the horizon — instant blindness will occur). Clear skies!