What’s in the sky this October?
Don’t forget that Daylight Saving Time starts at 2am on October 4th in NSW, ACT, Victoria, Tasmania and South Australia. Put your clocks forward one hour. If you rely on a smartphone the adjustment is automatic – but at least you will know why you seem to have lost an hour of the night.
Constellations are groupings of stars that have been given a name. For millennia they have been used as a tool to share significant cultural stories. Today, they also help astronomers delineate portions of the sky and are a navigational tool for locating astronomical objects. Use the map above, or the downloadable version, or your smartphone app, to help you navigate the sky. This month these constellations dominate the winter sky:
- Crux – The Southern Cross is in the south-east in October and upside down each evening. Around midnight it reaches its lowest point in the sky, very close to the southern horizon. It will be difficult to spot unless you have an unobstructed view due south.
- Scorpius – this is your final chance this year to spot the Scorpion as he dips into the western horizon. If you have a very dark sky (and the Moon is not up) you will see Scorpius hanging by his hooked tail from the Milky Way as he descends.
- Capricornus – an odd creature composed of a goat’s head and forefeet joined to the tail of a fish. Like Scorpius Capricornus is a zodiac constellation – one through which the Sun passes – and amongst the most ancient of constellations. The Greeks identified him with Pan, their god of the countryside. He was a naughty little goat who chased women. One attempted conquest failed when his target leapt into a river and turned herself into a bunch of reeds. Grabbing the reeds Pan heard the wind blowing tunefully through them – and the Pan flutes were born!
- Grus – just to the south-east from Capricornus, but still high overhead, is a bright star. This is Fomalhaut, the mouth of Pisces Austrinus, the Southern Fish. But I only mention this because it’s a guide onwards to the constellation Grus, the Crane. A modern constellation (well, dating from the 1500s!) it looks to me more like a scimitar with a great curving blade and it’s one of my favourite Spring constellations. Being a modern constellation there are no stories associated with it.
- Cygnus – the Swan is low by the northern horizon in October. Stories connected to Cygnus are somewhat convoluted but one has Zeus in disguise as a Swan on his way to seduce the, uninterested, nymph named Nemesis. Nemesis produced an egg from which hatched the beautiful Helen of Troy. The tail of Cygnus is marked by the bright star Deneb. This blue-white star is a giant, over 100 times the size of our Sun. Even at its vast distance of 3000 light years it’s still amongst the brightest stars in the sky. If it were as close as Alpha Centauri (4.5 light years) it would cast shadows at night!
This month Mercury, Mars, Jupiter and Saturn are our evening planets while Mars and Venus grace the morning sky. If you have trouble identifying planets from stars the Moon comes to your aid.
- Mercury – is low in the west in the evening sky and moving from Virgo into Libra but fading into the twilight around the middle of the month. If you have a clear and low western horizon a thin crescent Moon will be above and right of Mercury on the 18th.
- Venus – is low in the east in the morning twilight. On the 14th the Moon is below and left of Venus.
- Mars – the red planet is at its best this month. Don’t miss it! It’s in the east early in the night, overhead by midnight, and low in the west by night’s end. Mars is at its closest (to Earth) on the 7th and at its brightest on the 14th. In fact, it’s at its closest for two years and won’t be this close again until 2033. It doesn’t look very ‘red’, just a golden-orange colour but it is one of the brightest objects in the sky this month. Through a telescope you may get to see the patchy surface markings (if another planet-wide dust storm hasn’t blown up) and a bright spot of polar ice on one limb. The Moon is nearby on the 2nd and 3rd and again on the 29th and 30th.
- Jupiter & Saturn – the giant planets of the solar system are both high overhead in the early evening. On the 22nd and 23rd the crescent Moon passes by. These planets are gradually drawing closer together heading for their very close conjunction in December.
- The Orionids – not a planet but still part of our solar system, the Orionids meteor shower will be active all month, with the best nights being around the 21st. These meteors originated as dust expelled from Halley’s comet and they are often fast and bright. Look north after midnight for a few days around the 21st for meteors radiating from just below Orion’s red shoulder star, Betelgeuse. Be patient, it might be a few minutes between each one.
For the monthly movements of the moon, check out our Moon Phase Calendar.
Explore the universe through your binoculars or a telescope and take in some of the gems of this month’s sky. These look at their best with no Moon in the sky:
- The Magellanic Clouds and 47-Tuc – with binoculars look south for our neighbouring galaxies the Large Magellanic Cloud and the Small Magellanic Cloud (SMC) both of which are around 200,000 light years away from us. You will see fields of stars and maybe a hazy nebula. Beside the SMC the fuzzy, dandelion-like star you see is in fact the globular cluster known as 47-Tuc. Measurements of its distance vary from 13,000 to 16,000 light years. It is a ball-shaped group of stars on the edge of our galaxy and contains hundreds of thousands of ancient stars most of them several times older than our Sun.
- Turn your binoculars northwards to spot little Delphinus, the dolphin constellation, and then scan slowly along the Milky Way to spot clusters and nebulae galore.
- Mars, Jupiter & Saturn – are targets for a telescope if you have one. Watch Jupiter’s Moon Io play hide & seek with the planet (predictions available here) and then turn to Saturn to marvel at his rings.
- The Ring & Lagoon nebulae – with a larger telescope, one with computer control, you can easily locate the Ring nebula, M57, a ‘smoke ring’ blown off by a dying star. And finally, under Moon-less and dark country skies, dive into the Lagoon nebula…and contemplate the grandeur and timeliness of our vast and surprising universe.
An historical note to wrap up October 2020
October 17 marks 200 years since the birth of French astronomer and mathematician Edouard Roche. In 1848 he developed the theory of the Roche Limit which determines how close a moon can get to its parent planet before tidal forces tear the moon apart. Some time in the distant past a moon of Saturn passed inside the Roche limit, disintegrated, and formed the planet’s amazing rings.
- Purchase the 2020 Australasian Sky Guide by Dr Nick Lomb, featuring an annual report of what’s in the sky and the latest astronomical findings. Produced by MAAS Media.
- View the October Sky Chart, which shows the stars, constellations and planets visible in the night sky from anywhere in Australia
- Check out these resources for getting started