Autumn has arrived again and the nights are getting longer. After a good days walk, the sky will now be dark enough to stare up at the autumn skies before hitting the sleeping bags. This year, as well as the usual spectacular night skies there is also a lunar eclipse and some planets to brighten up the autumn night.
The nights of the autumnal full moons are Friday March 6, Saturday April 4 and Monday May 4. While nights on and around the full moon are great for not tripping over things in camp, or night walks, they wash out the magnificent canopy of stars.
However, on Saturday April 4 there will be a total lunar eclipse to enliven the night. From 8:45 pm ACDT the Moon will look to have a chip taken from its side. As the night wears on more and more of the moon will go dark as it is covered by Earth’s shadow and more and more stars come out. Finally at 10:30 pm ACDT the Moon will be fully covered. It does not disappear; it shines with a coppery glow, a burnished coin set amongst the stars. After a scant six minutes Earth’s shadow slips off the moon and it slowly reappears again.
Three bright planets grace the autumn skies: Venus, Jupiter and Saturn. Bright Venus is easily visible low in the western skies during twilight. It never really gets very high in the sky, so you need a fairly level, clear horizon to see it. On March 23 the crescent moon is close to Venus and on April 21 the crescent moon, Venus and the bright star Aldebaran make a triangle in the north-western sky.
Jupiter is the second brightest object in the sky after Venus (and the Moon and Sun of course). It is visible above the northern horizon at the start of autumn, easily recognisable by its brightness and its warm yellow colour. In case you have difficulty deciding, on March 3, March 30, April 26 and May 24 the waning Moon is close to Jupiter. If you have binoculars with you, Jupiter’s moons are easily seen in even small binoculars. At the start of autumn Jupiter is close to the Beehive cluster in Cancer, a faint but pretty cluster easily seen under bush skies.
As autumn progresses, Jupiter moves from the northern to north-western skies, and moves away from the Beehive towards the bright white star Regulus. By the end of autumn, Venus and Jupiter can be seen together in the early evening skies.
Outside the city and suburbs, the sheer number of stars can paradoxically make identifying constellations harder. One obvious constellation is Orion. The “saucepan” that marks Orion’s belt is easily seen above the north-western horizon once full dark has fallen. Above the “saucepan” is the brightest star in the sky, Sirius in the head of Orion’s hunting dog, Canis Major. During autumn Orion gets lower, and vanishes around mid-autumn. At the same time, Orion’s nemesis, Scorpius the scorpion, rises in the east. The distinctive curled question mark of Scorpius is very easy to pick out.
The head of Scorpius is defined by three bright stars to the left of a bright red star in the body of the question mark (Antares). However, if you look this autumn, you will see what appears to be four bright stars! The bottom and brightest ”star” of the four is in fact the planet Saturn, and it will stay in the head of the Scorpion for all of autumn.
Autumn is a great time to see the constellation of the Emu. This indigenous constellation is made up of dust clouds and the dark right of the Milky Way, and it is really only visible under the dark skies of the bush. It is best seen around mid-autumn when its distinctive shape is high enough to see before midnight.
Looking south, the Southern Cross and the two Pointers are obvious around midway between the zenith and the horizon. The Coalsack Nebula, a dark area clearly visible under dark skies between the Cross and the Pointers, is the Emu’s head. The dust lanes below the pointers form the Emu’s neck and the dust lanes around the curl of stars that marks Scorpius’s tail is its wings and body. Once seen this “dark constellation” is obvious.
There is a lot more to see in the autumn skies, just let your eyes roam!
Dr Ian Musgrave is a bushwalker and blogger who describes and interprets the night skies in SA.