Eye on the Night Sky in Whitby - September

Northern Milky Way - can be seen above Whitby in September
Northern Milky Way - can be seen above Whitby in September

Planetary Skylights

With Saturn having now departed, Venus is also very low in the WSW evening sky and almost lost to view. Both Jupiter and Mars can be located in the post midnight - early morning sky.

Jupiter rises before 1am by mid month and is the most conspicuous object visible in the east before dawn.

Mars is visible a couple of hours after Jupiter, being much fainter and orange in hue. The moon lies close to Jupiter on the 28th.

The Autumnal Equinox

Meteorological autumn may have started on September 1, however autumn officially commences in the northern hemisphere at the autumnal equinox, which this year falls on September 22.

At this point, the polar axis of our planet is again ‘square’ on to the sun and all locations receive equal hours of daylight and darkness.

From our vantage point, the Sun re crosses the celestial equator, retreating southwards, arcing ever lower above the southern horizon, its warming rays diminishing in intensity as it does so. Days grow shorter.

The Celestial Ocean – This Island Universe

Many amateur astronomers regard late September as one of ‘the special’ periods in which to explore the night sky. Conditions outside are often observer friendly; not too cold, clear, while skies are fully dark shortly after 9pm.

One of the heaven’s most celebrated features is also 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.

Fortunately, the North Yorkshire Moors still offer up numerous dark oases from which to fully appreciate our galactic heritage.

Choose a moonless period, (toward the end of September, early October) and allow time for your eyes to adapt to the conditions 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 4,000 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 arm’s, the nearest of which lies 6,500 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 perhaps 200 billion other stars about which orbit at least trillion planets (estimates continue to rise) Is it unreasonable to suppose that on some of these world’s alien eyes are also looking out, wondering about the majestic river of light?

Westerdale Star Party

Members of the Whitby and District Astronomical Society will be hosting a star party at the newly refurbished village hall in Westerdale on September 27 from 7.45pm.

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.

The first of the society’s monthly meetings after the summer period will be held on October 1 at Whitby Community College, main block, room H1 from 7.30pm.

If you have an interest in the night sky – are complete beginners, or want to purchase a telescope, then please do come along.

For more information please contact Mark Dawson, Whitby, on (01947) 605516 or e-mail spanton33@talktalk.net

Also you can visit www.whitby-astronomers.com