With the longest day of the year imminent for those of us in the northern hemisphere, we will no doubt be hoping to enjoy a little more sunshine and warmth each evening than in the months just passed! This however does not preclude there being some really fascinating sights to see in the heavens when the nocturnal star show commences.
Ninety degrees to the right of where the Sun has set (north) and at the highest point above you in the sky, you will find a long and rather snake-like pattern weaving its way between the Bears, Cepheus, and Hercules. This star pattern has a number of rather unique features which sets it apart from the other constellations embroidering the celestial sphere. As a ‘circumpolar’ constellation wrapped around the Pole Star this star pattern will never drop beneath the horizon, thus making it a great target for identification not only this month, but at any other time of the year. Having already described its shape you may have shrewdly judged this to be a creature rather than a person or character. Draco, Latin for ‘dragon’ originated in a garden-of-Eden-like myth involving females, a tree of apples, a monster, and a hero. The constellation that never sets therefore took the role of ‘Ladon’, the 100-headed monster that never sleeps. Guarding a tree of golden apples in a magnificent garden under the stewardship of the Hesperides (daughters of Atlas and Venus, also known as Hesperus), its final battle was with Hercules. However the plot thickens in one version of the story as the steward’s father, Atlas, became Hercules’ accomplice. In this dramatic twist Hercules’ great strength was put to the test as he temporarily bore the world for Atlas on his back while his tag-team partner slew the fearsome dragon.
The constellation of Draco proudly contains a ‘Pole Star’ among its number. This is a star that lies directly above Earth’s north Pole (and axis of rotation), albeit far out in space. However Alpha Draconis or Thuban to give the star its proper name, meaning “snake”, abdicated this unique role some 4000 years ago when Earth’s very slow motion spinning-top-like ‘wobble’ along its axis reselected Polaris in Ursa Minor as the Pole Star. That said, to this day the Great Pyramid of Giza in Egypt touches its forelock to Thuban as it contains a passage whose prospect looks directly out on the star. It is predicted that Earth’s sporadic axial wobble, a process known as ‘precession’ should restore the title of Pole Star to Draco’s once famous blue-white giant star by the year 21 000 AD. According to its orientation at this time of year, and if viewed facing north, Draco will look a little like a sprawling capital ‘N’ with the creature’s head rising from the tail of the letter up at the zenith. The head contains the pattern’s brightest star, Eltanin or “Zenith Star” which will have a more reddish hue. At the other end of the dragon Thuban’s dim radiance should be discernible as the brightest of the few stars located not far from the halfway point between the star marking the head of the little bear and the bright star in the tip of the tail of the Great Bear.
With planets outside our solar system known as ‘exoplanets’ and a grand total of as many as 889 discovered to date, the constellation of the dragon contains one of special significance. Although the majority of this number are composed of Neptune-Jupiter-sized gas giant planets (which potentially makes them easier to spot in the first place), one rocky Earth-sized planet once considered to be a possible candidate for hosting alien life, was observed in January 2011 by NASA’s Kepler spacecraft orbiting Kepler-10, a star that lies within Draco’s patch of sky. Despite the fact that subsequent investigations have revealed Kepler-10b, to give the planet its designated name, to be an inhospitable Venus-like world (thus eliminating its chances of supporting extra-terrestrial life), the fact that it was the first extra-solar terrestrial planet to be discovered is in itself an accolade of some distinction. For the majority of us however this star and its planetary system of at least two planets will remain shrouded in mystery, as the distant and extremely dim 10.9 magnitude Kepler-10 cannot be detected by the naked eye. The constellation of Draco also contains a nice selection of “Double Stars”. These are stars that at a first glance appear to be single celestial objects, however when inspected more closely reveal themselves to actually be two separate points of light, two stars in very close visual proximity to one another. One such pair can easily be found within the dragon’s head as the dimmest of the four stars of the quadrangle. Even a pair of binoculars will reveal Nu Draconis’ secret and split its light into two sources.
June affords us not only a great opportunity to find one of the most famous creatures from the rich Herculean myth, but to also locate the hero himself. Known to the Greeks as Heracles, the Romans referred to him as Hercules. When provocation by Hera, Hercules’ stepmother to a mad anger led him to commit murder, only the fulfilment of twelve years of service along with the completion of ten seemingly impossible challenges or ‘labours’ promised him atonement for his guilt. Since his efforts at slaying the Lernean Hydra and cleaning the Augean stables were not to the satisfaction of king Eurystheus who assigned Hercules the tasks, two additional ones were given him instead. According to the famous Greek myth the ten labours which Hercules undertook and ultimately completed with success were: To kill a Nemean lion; to bring a red female deer from Ceryneia; to acquire a live Erymanthian boar; to drive away Stymphalian birds; to capture a Cretan bull; to fetch the man-eating horses of Diomedes; to bring back the belt of the warrior queen Hippolyte; to attain the cattle of the monster Geryon; to steal the golden apples of the Hesperides; to kidnap Cerberus, beast of the Underworld. With the occasional aid from sympathetic deities Hermes and Athena, Hercules’ virtuous and eventually victorious struggles rewarded him with immortality.
Although this constellation is already adjacent to Draco we will have to reposition ourselves and concede to viewing him upside down if we wish to avoid neck strain! So from the direction you are facing make an about turn so that you can examine the southern sky. In a steep diagonal left sweep of the heavens move up from Spica and Virgo to Arcturus. The collection of stars above and to the left of Bootes’ kite-shaped body is your observational target. The absence of bright stars along with the squat Virgo-like shape that should greet your eyes when you join the luminous dots between 10 and 50 degrees down from the zenith will tell you that you have found Hercules.
Stargazers in the northern hemisphere aspiring to glimpse the whole constellation of Libra above the celestial equator may discover that this month ought to provide an ideal opportunity for doing so. Facing you squarely in the south and low down in the sky Libra forms the pattern of stars immediately to the left of the bright star Spica. Commonly composed of eight stars of only average brightness, the scales of Libra were said to belong to Virgo, also known as the goddess of justice.
Returning a little closer to home to complete our sampling of the night sky for this month, we at last come to the planets. Despite the greatest planetary performances remaining consigned to last month’s grand triple conjunction finale, as Jupiter continues its decent to eventually set with the Sun, the 10th of June will dramatically see a crescent Moon emerging to fill the gap to the left of Venus and Mercury. Although during the second half of the month Mercury too will plummet towards the horizon, Venus, on the other end of the cosmic seesaw will be continuing its ascent into the night sky. Other highlights to look out for this month include the meteor shower known as the Lyrids, thought to come from an old stream of debris trailing behind Comet Thatcher (C/1861 G1) which our planet passes through on a cyclical basis every year. Generally observed as of bluish-white hue and moving fairly rapidly across the heavens, the peak of activity could display up to a maximum of eight meteors per hour on the 15th and 16th June. Although known for being the most Spartan and potentially least dramatic of the all this season’s meteor showers, the spectacle of seeing a shooting star is one of which we can never tire. Look high in the eastern sky to the constellation of Lyra on these dates if you would like to see a few naturally-occurring celestial fireworks.
Shooting stars, but not as we know them: Here is an Earthward view of the Lyrids meteor shower as seen from the International Space Station showing them appearing as tailless flashes of purple light as they strike Earth’s atmosphere at high speed.
So as you raise your eyes to the heavens to observe the great sights of the night sky in June, happy hunting and enjoy your interstellar voyage!
(Article by Nick Parke, Education Support Officer)