September Night Sky Wonders

Although the back-to-school month may see many of us locked away in ‘darkened rooms’ on more than one occasion, where curtains are left open we may just find our rooms once again graced with a little starlight.

With her bold letter-‘W’-like form grabbing your attention from high in the night sky, Cassiopeia, the circumpolar constellation named after the vain queen of Greek mythology, most likely takes pleasure in outshining the dimmer stars of her ‘downtrodden husband’ and adjacent constellation, king Cepheus. It was said that having already offended Poseidon’s golden-haired sea nymphs with her overt claims to superior beauty, the god of the sea’s punishment saw to it that Cassiopeia was toppled from her upright position and pedestal of self-regard while being placed in the heavens. Enslaved to the Pole Star and forced to endlessly circle it, Cassiopeia would forevermore frequently be found in an undignified fashion hanging upside-down or with her haughty eyes forced to look down at the ground.

In the northeast: The star patterns of Perseus and Cassiopeia in proximity to the Pole Star (marked with target), 10pm 15th September 2013.
(Image credit: Stellarium/Nick Parke)

If you ignore the final would-be line joining the last two stars of the constellation Cassiopeia’s ‘W’-like shape you should more easily be able to imagine the queen’s seated form. Look for the back of her chair currently attached to the ceiling of the celestial sphere, her shins therefore running near parallel with the horizon, and in your mind’s eye see her proud face looking down squarely at the Earth below. Beneath queen Cassiopeia in the night sky at this time of year we get a great opportunity to see another famous character of Greek legend. However once again the Greeks seemed to have ‘run out’ of stars for this constellation as only the stick figure form of the character’s torso, legs, and feet can easily be recognised in the heavens.

Perseus, son of Zeus and raised by his single-parent-mother Danae, was the legendary hero of Greek mythology who displayed great ingenuity and skill in defeating the formidable Gorgon Medusa. Where many before him had failed and been turned to stone by meeting the glare of the hideous snake-haired adversary, Perseus ‘looked for’ Medusa only in the reflection of his metallic shield, before suddenly turning and beheading it with one sweep of his sword. Originally sent on the mission for his intended undoing, king Polydectes’s hostile reception to the hero’s triumphant return so angered Perseus that he killed the king by holding up the head of the Gorgon so that the king’s gaze should fall on Medusa’s statue-forming eyes. While some may associate the ancient Arabic name ‘Ra’s Al-Ghul’ with the super-villain played by Liam Neeson in the movie Batman Begins, the star also known as ‘The Demon Star’ whose name actually means “head of the ogre”, has in reality represented the Medusa’s head as the second brightest star in the constellation of Perseus for centuries.

While this artist’s depiction of the mythical creature Capricornus crowned with the Moon on the 15th of the month may appear to be an appealing spectacle, the stargazer hoping to spot the sea-goat constellation’s dim outline of stars for real in the night sky, best do so on an evening before or after the Moon’s nocturnal reign.
(Image credit: Stellarium/Nick Parke)

Listed by the Greek astronomer Ptolemy in the second century and mentioned in Sumerian culture as ‘Suhur-mash-sha’ (the goat-fish), we find another mythical creature and sign of the Zodiac residing in the southern sky, the constellation of Capricornus the sea-goat. This roughly triangular star pattern has a goat-like head and upper body but with scales appearing on its torso and its hindquarters ending in a fish’s tail. Despite the star pattern’s visual obscurity in the heavens the creature’s place in Greek mythology is secure, as in one tale it was said to be Capricornus that nursed none other than the king of the gods, Zeus, when he was a baby. More popularly however this constellation was associated with the goat-legged god of nature, Pan, who was placed in the heavens after helping Zeus and the other gods conquer the Titans. When the beast Typhon tried to attack him, Pan guaranteed his own survival by taking the form of a goat. On jumping into the river Nile however the lower half of his body (unseen from the river bank) was changed into a fish.

9th September 10pm: Three steps you can take to see the constellation of Capricornus in the south.
(image credit: Stellarium/Nick Parke)

There are three simple steps we can follow to help us locate the sea-goat and second dimmest constellation of the Zodiac in the heavens. Firstly, we should start by looking just above the horizon in the south, below and a little left of Aquila’s bright star Altair. Secondly, we should search this patch of sky for the dim dot-to-dot perimeter of what will look like some huge shark tooth jutting out from a gum, with the tip of the tooth pointing east (see Stellarium image for reference). Within this dim collection of stars, the one marking the tip of the ‘shark’s tooth’, Deneb Algedi, and the two lining the gum will appear to be the brightest in the star pattern. If we get this far, we will have just discovered the constellation of Capricornus the sea-goat. The point of ‘the tooth’ in fact represents the fish-like tail while at the other end of the pattern your imaginary dot-to-dot line marking ‘the gum’ will form the sea-goat’s horns. In your mind’s eye connect the stars within ‘the tooth’ to make up a more sea-goat-like pattern.

So I wonder are you a little like me? When you hear the words ‘Milky Way’, ‘Galaxy’, or even ‘Mars’ does a sweet-sounding little bell go off somewhere in your head? If so, the man we have to thank for this is Franklin Clarence Mars. Since 1923 he and his family have tickled our taste buds and brought connotations of space into our kitchens, schools, and supermarkets. Although the Milky Way and Galaxy chocolate bars take their names directly from space, the third coincidentally ‘planet-titled’ chocolate bar instead was created by Mr. Mars’ son and in fact named after the family.

The Milky Way (right of arrow), 10pm northern latitudes: Best seen until the 10th of the month or from the 25th onwards, when a Moonless (and potentially cloudless) sky may give you a glimpse of it running through the constellations of Sagittarius, Aquila, Cassiopeia, and Perseus to name but a few.
Image credit: Stellarium/Nick Parke)

So what about the real Milky Way, the great star city in which we live? Well, September gives us another good month to observe our favourite spiral galaxy running right over our heads high into the night sky, where from this position it’s reduced competition with Earth’s atmosphere give us a much better chance of seeing it. That said thanks to the 21^st century light pollution only the darkest, most isolated regions of the countryside will provide a vantage point with reasonable observational prospects. Appearing to be a pale milky river starting in the SSW and running straight across space, when we see it we can remind ourselves that we are effectively looking through a large section of our pancake-shaped-galaxy’s 85 000 light-year-broad amassed plane of gas, dust and 300 billion stars.

M39 open cluster: In space, give them long enough and like people, some stars appear to prefer to ‘huddle’ together than stand alone. Behind this apparent stellar ‘social attraction’ however, is in reality only the somewhat more prosaic force of gravity.
(image credit: Heidi Schweiker/WIYN/NOAO/AURA/NSF)

But it’s that time again when we hit the light speed button and explore a little more closely, some of those other fascinating deep-space objects out there. Looking southeast we’ll start by focusing our gaze on a patch of sky within one third of the visual distance between the bright left-most star forming the base of the isosceles-shaped Summer Triangle high in the sky (Deneb in the constellation of Cygnus), and where queen Cassiopeia’s head should be, farther north in the night sky. Looking a few degrees beneath this zone you should be able to see with a small telescope the open cluster of stars known as Messier 39 (or M39 for short). M39 contains stars approximately 300 million years old, much younger than even our Solar System’s star and which are located just 800 light years away within the plane of our galaxy’s disc. As one of the biggest open clusters in the northern sky however, its stellar inhabitants are much more spread out that would be in other similar structures.

Best explored in a Moonless sky: The impressive star gatherings Messier 15 and Messier 39, SE 9th September 2013. (Image credit: Stellarium/Nick Parke)

However if you lower your gaze and look a little farther over to the right, you might just be able to spot without an optical aid, a fuzzy grey spot called Messier 15. If you shoot an imaginary line up from the ‘tail’ star of the constellation of Capricornus and then continue your line, banking at a sharp right angle towards Altair in Aquila, the sky zone in the corner of the right-angle and just beside the star Enif in Pegasus is where a pair of binoculars should reveal something special. This ancient jewel of the Universe, a spherical collection of still-mysteriously-brilliant stars continues to fascinate both the professional and amateur astronomer alike. With M15’s estimated 13 billion year old stars densely populating such a small proximity of space, they serve to make it one of the most eye-catching globular clusters known. This spherical conglomeration of stars are as far as 35 000 light years from Earth, with most of the cluster’s stars having been pulled together into a tightly-knit clump at its core thanks to the suspected process of gravitational ‘core collapse’.

Give Pease a chance: M15 is the first of four galactic or globular clusters discovered to contain a spherical ‘planetary’ nebula. Although sadly void of greenish hue Pease 1’s small blue form can just be spotted in the lower left of M15’s core.
(image credit: ESA/Hubble & NASA)

Other things to look out for this month include the crescent Moon on the evening of the 8^th September, as it will be putting on a luminal ‘double-act’  just a few degrees south of Venus, while the next day the Moon will again display her white beauty south of Saturn. For our Red Planet enthusiasts a pair of binoculars looking east in the predawn sky should also reveal our terrestrial neighbour Mars (passing in front of the constellation of Cancer) on the 8^th and 9^th September. As far as planetary double-acts go the sight of Venus (glowing at magnitude -4.0), lying only three and a half degrees to the south of our Solar System’s best-ringed planet on the 18^th might make this another date worth circling on the calendar for a little outdoor observing. A ‘Harvest Moon’ or Full Moon nearest the date of the Autumnal or Southward Equinox (22^nd Sept. 8.44pm), should all being well illuminate our night sky on the 19^th, rising in an increment of only about half an hour later than it did the night before. Finally by the 28^th and 29^th of this month our lunar enthusiasts may be delighted with the prospect of also seeing the Moon in close conference with the gas giant Jupiter in the hours of the morning. Currently making its way across the constellation of Cancer the crab, we can only hope and wait with pleasurable anticipation for our cool cosmic visitor, Comet ISON, to start to put on a more dramatic celestial ice show, perhaps even as of next month.

So as you raise your eyes to the heavens to observe the great sights of the night sky in September, happy hunting and enjoy your interstellar voyage!

(Article by Nick Parke, Education Support Officer)