Galaxy neighbours

Ken Kennedy of Dundee Astronomical Society tells us what we can expect to see in the October sky.

“What I think of as the first of the great winter constellations, Pegasus, straddles the meridian later on October evenings,” he says. “The square formed by the corner stars of the horse’s body is easy to see but, unless you remember that Pegasus is inverted, the neck and legs are less obvious.

“The neck stretches from the lower right hand star of the square, Markab, westwards and ends at Pegasus’ nose, the star Enif. Project a line along the stars of the head through Enif and you arrive at Messier 15, another of the many globular clusters which surround the Milky Way galaxy.

“Sadly for those of us who enjoy looking at the night sky, modern LED street lighting is intrusive despite sending less light upwards. For those below the lights it is almost impossible to see more than the brightest stars. The number of stars visible within the Square of Pegasus has long been a test of how clear the sky is and, in good conditions, it may be possible to see nine, or even a few more.

“The left or eastern edge of the Square marks the limit of Pegasus and what appears to be its hind leg is actually the constellation of Andromeda and the top left hand star of the Square, Alpheratz, is now classified as being in Andromeda.

“Looking eastwards along the stars of Andromeda we come to two of our local neighbouring galaxies, Messier 31, and Messier 33 in Triangulum which I will mention next month.

“The first of the series of winter meteor showers peaks between October 21 and 23. This year the Orionid meteor shower is favourable for observation as the moon will be only three days old on the 22nd and, because this shower does not have a very sharp peak, good numbers of meteors should be seen during a number of nights.

“At maximum 25 meteors per hour can be expected and these are fast, often with persistent trains lasting a few seconds. The Orionid meteor shower is associated with Halley’s Comet and the flashes of light seen crossing the sky are particles released from the comet on its many orbits round the sun. As with all meteor observations, watch for them in the darkest part of the sky from your observing site.

“Mercury will not be visible throughout October. Venus is still bright in the morning sky before sunrise but will close in on the sun and becomes quite low by the end of the month.

“Mars is much fainter than Venus but will be very close to it on the morning of October 6. Jupiter is too close to the sun to be seen this month. Saturn sets at around 8pm and is likely to be lost in twilight before setting.

“The moon is full on the 5th, at last quarter on the 12th, new on the 19th and at first quarter on October 27.”