Ancient stars

Ken Kennedy of Dundee Astronomical Society tells us what to look for in the June sky. “The Plough sits high in the late evening sky with its handle pointing towards the constellation Boötes with its brightest star, Arcturus, still shining quite brightly in the never dark skies this month,” he says.

“Jupiter is even brighter below and to the south west of Arcturus and from these markers we can perhaps make out the fainter constellation of summer. The Summer Triangle of Vega, Deneb and Altair can be clearly seen in the eastern sky as these stars stand out at even a casual glance.

“However, if you look carefully between the Summer Triangle and Arcturus there are a number of fainter stars which form the interesting constellations of Hercules and Corona Borealis.

“Although Hercules contains no particularly bright stars it is ranked fifth in size among the 88 constellations.

“Rather like Pegasus, Hercules is depicted as being upside down from the northern hemisphere with his left arm pointing towards Lyra and his left leg standing on the head of Draco, the dragon killed by Hercules in his quest for the golden apples.

“It’s not difficult to imaging this inverted hero in the sky as part of his lower body if marked by four stars forming the Keystone. Between the two right hand stars of this obvious shape lies the bright globular cluster Messier 13.

“The Hercules cluster is one of the best of the 150 or so globular clusters which surround our Milky Way galaxy. They all consist of ancient stars, some of which are more than 12 billion years old. How they formed is still controversial with a number of competing theories being held by astronomers.

“June brings the first full summer month of noctilucent clouds (NLC), displays of which should be well under way by the middle of the month.

“Remember to have a look to the north on clear nights from about an hour after sunset and you may be rewarded by a fine display of these very high, pearly white ice clouds. They tend to be more frequent at times near solar minimum.

“The summer solstice, when the sun reaches its highest point in the sky, will occur this year on June 21 at 5.24 BST when the length of day between sunrise and sunset will be more than 17.5 hours in Scotland.

“Mercury moves eastwards towards the sun until June 21 when it will be behind the sun and will not be visible throughout the month. Venus will be low in the east, rising about an hour and a half before the sun at around 3am midmonth.

“Mars sets only half an hour after the sun during June and will not be visible. Jupiter is still bright in the south-west as the sun sets, itself setting in the west at 2am. Saturn is low in the south at 1am and sets at around 4am.

“The moon is at first quarter on the 1st, full on the 9th, at last quarter on the 17th and new on June 24.”