with Dr David Weldrake
Milky Way, galaxy central, moves to the west
October is a transition time when the bright stars and vast Milky Way of winter start to give way to the fainter stars of spring. The Milky Way is starting to settle towards the west after sunset, with the bright red star Antares leading the way. Rising in the east to take it’s place are blue white Fomalhaut and white Canopus.
Low in the north are white Vega and blue white Altair, with yellow Alpha Centauri completing the picture towards the south west.
The Milky Way we see defines the central disc of our galaxy. As the Milky Way moves towards the west during spring we start to see the space around its southern pole. This provides a clear line of sight, and we can see many other more distant galaxies. Indeed, during spring, thousands of them are visible across the sky through backyard telescopes, visible as very faint smudges of distant light.
The planets in October: Mars and Saturn continue to shine
October, as per last month allows us a continued chance to see Mars and Saturn, shining in turn as reddish and yellowish ‘stars’ towards the west after sunset. In between the two is the red star Antares, in the constellation Scorpius
Eagle eyed people can also spot tiny Mercury, appearing as a fairly conspicuous white ‘star’ low in the west after sunset. Mercury moves very quickly, as it is the closest planet to the Sun, and will only be visible for the first part of the month.
Jupiter and Venus are also visible, although early in the morning. Look for two very bright ‘stars’ in the east before sunrise. Jupiter is higher up the sky, and Venus rises just before the Sun. Venus will return to our evening skies early next year.
October 8 total lunar eclipse, red or purple
October gives us an excellent opportunity to see a total lunar eclipse, which occurs this month on the evening of 8 October.
Lunar eclipses occur at the time of full Moon, only in this case the Moon passes into the shadow cast by the Earth. As the Moon shines purely by reflected sunlight, moving into the Earth’s shadow causes it to fade out, gradually going dark over a period of an hour or so.
Once the Moon is totally immersed in the Earth’s shadow, a period called ‘totality’, it can turn a dark red or purple colour, before gradually moving out of the Earth’s shadow and resuming it’s normal appearance. During totality, lunar eclipses can be a variety of different colours.
The Earth’s atmosphere causes light to be bent or ‘refracted’ onto the Moon during the eclipse, and if the atmosphere has lots of dust in it, caused for example by a volcanic eruption somewhere in the world, then the Moon will look very dark. If the Earth’s atmosphere is clear of dust, the Moon will be a brighter red. This time around the Moon should be a fairly bright reddish copper colour, but it is very hard to predict exactly what it will look like.
Lunar eclipses occur fairly regularly, but sometimes we have to wait a couple of years for the next one. The most recent was back in April, and the next is due in April 2015. The reason they tend to happen at around the same times of the year is no coincidence; the alignment of the Earth, Moon and Sun occurs more frequently around the equinox.
The first phase of the eclipse will occur at 8:18pm, after which the Moon will gradually move into the Earth’s shadow, and will be totally eclipsed at 9:27pm. Between then and 10:22pm the Moon will be a coppery red colour, before moving back out of the shadow again and back to normal by 11:32pm.
Lunar eclipses are there for all to see, they do not require any optical aid, just a clear sky and are well worth a look. Don’t miss this opportunity!
For October the Moon is at first quarter (half phase) on the 2, full on the 8 (hence the lunar eclipse), at third quarter on the 16 and new on the 24.