The Courier & Advertiser (Fife Edition)
Coming out of the darkness
Most people are usually delighted to see longer evenings beginning in earnest during May – but it can be a bittersweet dawning for dedicated skywatchers.
Looking ahead to the prospects of potential stratospheric displays in the month ahead, Craigie’s resident stargazer Ken Kennedy explains: “Twilight diminishes during April and by the second of May true darkness only occurs for 32 minutes after which, until the 10th of August, true darkness does not return.
“The summer constellations are much less dramatic and bright than those in winter months, but the brightest stars which indicate the summer constellations can still be seen during darker times of the evening.
“Regulus, in Leo, can be seen towards the south-west while Arcturus of Bootes is high in the south by 10pm. By that time, the Summer Triangle of Vega, Deneb and Altair are rising in the east to north-eastern sky.
“Finally, looking north-west, the bright yellow star Capella will be seen in a northerly direction throughout the summer months.”
The Dundee Astronomical Society stalwart goes on: “The seven stars of the Plough are nearly overhead in late May evenings, with its handle pointing towards bright Arcturus, making it easy to identify.
“Have a look at the handle of the Plough and in particular the second star from the handle’s end. This star is called Mizar and, if your eyesight is better than mine, you may see another star close to Mizar.
“This is named Alcor and may be seen more easily using binoculars. This pair of stars move together in the sky at a distance of 82 light years and it has been discovered that they are bound by gravity – and orbit each other in about one million years.
“The pair Mizar and Alcor also have companions making a total of six stars in the multiple complex, a striking contrast to our own solitary sun.”
With stellar activity becoming more tricky to observe, Ken says attention is likely to focus on other features in the sky.
He points out: “The end of May should see the start of the noctilucent cloud season. Because of warming in the lower layers of the atmosphere, tenuous ice clouds form at an extreme height of around 85km and these have regularly made their first appearances in the last week of May.
“They are so thin that they can only be seen after sunset, from about 10.30pm until 3am, explaining their name – which can be translated as ‘night-shining clouds’. These pearly-white clouds are generally seen to the north but can be quite extensive.
“There is evidence to suggest that high ice clouds such as these are associated with global climate change but may also be influenced by solar activity. They are best seen during June and July and usually end around early August.”
He adds: “I have previously mentioned the star Capella of Auriga and this swings round above the northern horizon as the evenings progress. It is one of the best markers for the position of noctilucent clouds, and photographs taken often show bands and ripples of the ice clouds round it.”
Ken will look at planetary prospects for May in a postscript in tomorrow’s Craigie.