September is possibly my favourite month, nights are dark reasonably early and you don’t have to don Arctic clothing in which to observe.
In the night sky, the Milky Way is at its best as seen from the UK and there’s plenty on offer to tempt the observer, particularly after midmonth when the moon is waning and we have dark skies.
Talking of the moon September’s Full Moon is actually another ‘mega moon’ event, Augusts’ mega moon (the biggest of the year) having been clouded out on that awful Regatta Sunday.
Dependant of weather conditions on Tuesday September 9, have a camera to hand in readiness for moon rise around 7.45pm. September is also the month of the autumnal equinox; equal hours of light and dark again, after which there is more dark in the equation as days grow shorter and the northern hemisphere tilts away from our nearest star.
The actual date of the equinox is a little later this year, September 23 at 3.30am in the morning.
Planetary wise, Mars and Saturn remain on view, low in the WSW evening twilight sky, but will become increasingly difficult to observe as the month progresses.
Mars is trying to keep ahead of the Sun and will lie well to the right of Saturn. The red planet is in conjunction with its nemesis Antares – ‘the rival of Mars’ - chief star in Scorpius on the 29th when also the moon is close by.
Jupiter and Venus both lie in the dawn sky. Jupiter is quite high up in the east an hour before sunrise and should be easily recognizable, whereas brilliant Venus lies deep in dawn twilight very low to ENE horizon.
The moon lies near Jupiter on the 20th.
Many amateur astronomers regard late September as one of ‘the special’ periods in which to explore the night sky. Conditions are often favourable, and apart from a wealth of deep sky objects to view, one of the skies most celebrated features is seen at its best during this time, the summer Milky Way.
Sadly for many inhabitants of the UK this magical aspect of the night sky is all too often rendered invisible because of light pollution. At least round these parts, the moors and coast still offer up numerous dark oases from which to fully appreciate our galactic heritage.
Choose a moonless period, mid month onwards this September, and allow your eyes time to light levels, before attempting to trace the path of the Milky Way through the brilliant starry canopy above.
On a clear, dark night you will discern the Milky Way stretching across the heavens from the NNE horizon, where it flows passed conspicuous Capella in Auriga, dissecting the sky overhead, before flowing down through Sagittarius on the SW horizon.
In-between the milky waters sweep through Perseus and into the familiar ‘W’ pattern of Cassiopeia, where it is worth while spending some time exploring a plethora of star fields and clusters using a pair of binoculars or better still a telescope. Moving through Cepheus, the Milky Way then passes overhead, directly through the long axis of Cygnus the swan (also known as the Northern Cross).
Here, nearby its chief star; Deneb, the milky stream divides as though passing either side of a long island midstream. Known as the ‘northern rift’, in reality this is a vast obscuring dust cloud hundreds of light years in length and some 4000 light years distant that blocks out the stellar multitude beyond.
The two courses continue on down through Aquila, highlighted by the most southerly star of the ‘summer Triangle’, bright Altair, before broadening through Scutum, a small constellation rich in galactic objects.
The river finally spills down over the SW horizon through Sagittarius, an area awash with nebulae, star clusters and dust clouds, hidden within which resides the centre of our galaxy.
Revered by ancient civilizations as a divine water course or spiritual path guiding the soul of the departed into the afterlife, even today the sight of the Milky Way can be magical experience.
The true nature of this mystical ghostly light has now been understood for over a century, however, it is only in the last decade combining data obtained from across the electromagnetic spectrum that astronomers have developed a clearer, more refined picture of our stellar metropolis. Our galaxy is now classed as a ‘barred spiral’ some 90 –110 thousand light years in diameter with just two major arms and two lesser ones.
The major spiral arms, the nearest of which lies 6500 light years away, are around 1,500 light years thick.
The central bar consists of stars orbiting in highly elliptical paths and is approximately 28,000 light years in length, bulging at the centre by some 12,000.light years.
Our own Sun is located on the edge of the ‘Orion spur’, midway between two major arms and regarded as a fairly quite stellar neighbourhood approximately 26,000 light years from galactic centre. At the very heart of our galaxy lurks a black hole that feeds’ on any star straying too close.
There is strong evidence to suggest that like many galaxies, our galaxy has cannibal tendencies, having absorbed several dwarf galaxies over the millennia. Astronomers now believe that some of the many globular clusters visible around the periphery of our galaxy are in fact the central cores of these.
So when you next gaze up in awe at the Milky Way, ponder this. Within our ‘island universe’ the Sun is just one of some 200 billion other stars around which at least one trillion planets orbit (very conservative estimate). Is it unreasonable to suppose that on some of these worlds alien eyes are also gazing upwards and outwards, wondering about the majestic river of light? Our ancestors would be utterly amazed!
Members of the Whitby and District Astronomical Society will be hosting a star party at Westerdale village hall on September 13 from 8.15pm. We shall be bringing along a number of telescopes with the intention of showing numerous deep sky wonders visible in the early autumn sky. An indoor presentation will be given if skies are cloudy.
Whitby and District Astronomical Society will be hosting public star parties on the Cook headland area – West Cliff on September 9, 12 and 20 from 8pm.
For more information email Mark at email@example.com, call him on (01947) 605516 or visit