Written by Nick Parke
Well hello again and welcome to another edition of the night sky for the month of September! Hoping that you’ve been able to enjoy plenty of long summer days and sunshine over the summer period. Perhaps you’re already anticipating with pleasure some cooler evening temperatures and the stillness of a darker night sky full of shimmering stars… so let’s begin our September night sky tour!
Turning a little to the right of where the Sun rises in the morning, let’s look for a few things in a southerly direction. High in the sky we can still see the ‘Summer Triangle’ asterism in all its glory with stars Altair, Deneb and Vega marking its vertices. This wonderful pattern – an easy one for all levels of stargazer to find will continue to put on its bright show right through into the autumn. Beneath this large pattern we can see the zodiac constellation – the “Sea-goat”, Capricornus. Not only is this the best month for us to examine this pattern, but mid-month it will be graced with the presence of, what in Roman mythology, was the god of agriculture, wealth and abundance – Saturn (the equivalent of ‘Cronus’ in Greek Mythology). Having overthrown his tyrannical father ‘Caelus’ (or Uranus in Greek mythology), Saturn represents the supreme god of the skies who would rule Latium with wisdom and who’s rule would be marked by peace.
Look for Deneb Algedi (also known as Delta Capricornus) which is the brightest star in Capricornus, marking the furthermost star from the creature’s head and is the only star with a magnitude brighter than (i.e. with a lower value than)- three, at magnitude 2.85. Connect four more stars to the right of it to draw the back of the animal up to the top of its head and you will have also reached the second brightest star of this constellation; Dabih Major, a double star. If you have any trouble locating the Capricornus constellation in the night sky, simply shoot an imaginary line from Vega in the Summer Triangle down through Altair and almost the same distance farther down again you will have reached the front knees of the ‘sea-goat’ passing through its starry head along the way.
The planet with the most spectacular rings of our Solar System lies just between the second and third stars along Capricornus’ back. Looking like a bright golden star, point a pair of binoculars or a small telescope at it if you can lay your hands on either for a better look at this striking planetary neighbour.
Looking East we can see the constellation of Lacerta, which is Latin for ‘lizard’. It is one of the 88 modern constellations and first appeared in Polish astronomer Johannes Hevelius’ Firmamentum Sobiescianum published in 1690. Unlike many of the ‘older’ constellations this one has no ancient mythology associated with it but was at one time referred to by its creator as ‘Stellio’ in reference to the European randomly-speckled species of lizard known as the Starred Agama.
The best way to be sure you are looking at Lacerta in the night sky is to triangulate its position between 3 constellations. Firstly to get a sense of where to look for the starry reptile, it’s located directly behind Cygnus’ right wing. Then if you put your finger on the orange supergiant star – Zeta Cephei (that marks the right shoulder in the square portion of the Cepheus constellation), from there you can draw your finger along the lizard’s spine running down and to the right. After Lacerta your finger should have arrived at the hooves of Pegasus, marked by stars Pi Pegasi (left hoof: a binary star system) and Kappa Pegasi (right hoof: a triple star system) respectively.
With the lizard being one of the dimmer and smaller constellations in the night sky it is less well known, however although its stars are only 4th magnitude stars they should still be visible on a good dark, clear night or more easily – from a dark-sky location. Moreover the challenge of observing it is made easier by the fact that its shape is extremely simple, looking just like a tadpole. The brightest star, designated Alpha Lacertae, marks the left-hand point of the narrow diamond-shaped head. With this star, unlike so many others in the night sky that hide their true identity – what you see with the naked eye is what you get, as it is a genuinely a ‘white’ single star that lies 103 light years from the Sun.
This pattern also happens to contain BL Lacertae which is blasar, a supermassive blackhole emitting powerful jets of energetic radiation from its poles far into Space. BL Lacertae became the prototype for these most fascinating of cosmic creatures with ‘active galactic nuclei’ (AGNs) and are therefore referred to as ‘BL Lac objects’. If you’ve heard of a quasar but not a blasar – don’t worry, they are essentially the same thing, that is, with one significant difference. With quasars – their jets are beamed into Space at an angle as perceived from our viewpoint on Earth. Blasars on the other hand are angled so that we are looking directly down the beam just as if a laser beam were being shone directly at us! Once mistaken for a rare type of variable star due to their brightness and therefore supposed close proximity, today we know them to be the brightest objects in the Universe, flashing signals from across intergalactic Space!
Closer to home and to finish our night sky tour for this month – why not treat yourself to a good look at the king of the planets, Jupiter (appearing like a very large white star) and still gracing the eastern part of the sky with its stolid regal gleam… You will find it above the tail of Cetus the sea monster (half-hidden beneath the horizon) and beneath the right hand-hand fish in the constellation of Pisces.
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!