Rich in star clusters

Ken Kennedy, of Dundee Astronomical Society, tells us what to expect in the October sky. “With autumn now well under way the Summer Triangle is still in the sky but is moving westwards,” he says.

“The bright star Vega, sitting between Hercules and Cygnus, dominates that more westerly sky, but being still at a high elevation reminds us that Cygnus and its associated objects of interest are still readily available this month.

“The square of Pegasus, made up of bright stars, is moving towards a southerly position by 10pm. The square is easy to pick out, but to see the horse you have to think head down, legs up, as Pegasus is inverted from northern latitudes. An observer south of the equator and looking northwards would see Pegasus in a much more dignified upright position as it crosses the sky.

“A rich section of the Milky Way passes through Cassiopeia and I recommend that you get your binoculars out again and scan the area covered by, and around, the letter W which marks the main area of the constellation.

“There are so many background stars in this area that it is difficult to pick out the shape of Cassiopeia, but it is easy to spot from urban locations.

“This area is rich in star clusters, all relatively young stars which have not drifted too far away from their siblings. Starting from the left-hand two stars of the W, have a look for NGC 663 and Messier 103. NGC 663 is 6,800 light years distant and the 400 stars it contains are about 20 million years old.

“Nearby Messier 103 is a bit more distant at 8,500 light years, but the stars are of similar age. It appears as a small diamond-shaped group of stars.

“Moving down just below the W-shape of Cassiopeia, you will come to another star cluster, NGC 457, also known as the Owl Cluster. Similar to Messier 103 in distance and age, two brighter stars which seem to form the owl’s eyes give it its name.

“For the fourth star cluster of our tour, Messier 52, follow the right-hand pair of stars upwards for about the same distance between these stars.

“This cluster is about 5,000 light years distant and about 35 million years old and may appear as a V-shape in binoculars.

“The maximum of the Orionid meteor shower occurs on the night of October 22/23 when the moon is waning and will not interfere significantly with observations. This is not a major meteor shower, with 20 meteors per hour expected at maximum.

“Summer time, or daylight saving time, ends on October 27 and allows astronomers throughout the UK to synchronise their observations with Greenwich Mean Time.

“Mercury and Venus both set at much the same time as the sun so will not be visible during October.

“Mars pulls away from the sun during the month and may be seen low in the east south-east by 6am, rising about two hours before the sun.

“Jupiter sets in the south-west at around 8pm and will just be seen for a short time low in the sky after sunset. Saturn, in the south south-west at the same time as Jupiter, sets two hours later at 10pm.

“The moon is at first quarter on the 5th, full on the 13th, last quarter on the 21st and new on October 28.”