A clear winter night is a delight for southern hemisphere astronomers as the centre of the Milky Way galaxy is in a perfect position for observing. As I was spending some time at my telescope eyepiece a couple of nights ago, I couldn’t resist getting the camera to capture the spectacle of the galactic centre rising over our driveway. Just down the road really!
The Galaxy rises!
The centre of the Milky Way is in the direction of the Arabic-European constellation Sagittarius – the centaur archer. While the bright stars of Sagittarius are all less than 100 light years away, the supermassive black hole at the centre of the galaxy is 25,640 light years from us and the galaxy itself is estimated to be 150,000 light years across. A light year is the distance light travels in a year – about 10,000,000,000,000 kilometres.
Also in this photo are the constellations Scorpius and Grus – the scorpion and the crane. Both of these constellations actually look like the beings the are named after, but the upswept wings of the crane are actually out of the frame at the bottom of the photo.
Gas giant planets Jupiter and Saturn can also be seen in this photo – about 50 and 80 light minutes from us, so very much closer to home.
The dark patches across the Milky Way are lanes of cold gas and dust, from which new stars will one day be born. At the top right hand corner of the frame, between two stars of the Southern Cross (Crux) is a dark gas cloud unpoetically called the Coal Sack by western astronomers. To indigenous Australian astronomers, this was the head of the giant emu, the shape made by the dark clouds along the Milky Way.
Many years ago, Newstead Landcare were fortunate to have a night under the stars with John Morieson who had studied the records of the astronomy of the Boorong people of Lake Tyrell in northern Victoria. They called the giant Emu Tchingal and it was a giant who ate people – perhaps the giant carnivorous megafauna emu that once roamed Australia. John told us of the fight between Tchingal and Bunya, the Ring-tailed Possum ancestor, who drops his spear whilst climbing a tree that we see as the Southern Cross. The spear is seen as the pointers – Alpha and Beta Centauri, whilst Bunya’s head is the top star of the cross (Gamma Crucis), his ears are two small stars above the cross and his tail is an arc of stars to the left of the cross.
Bunya and his spear and tree
I pointed the camera south to capture more of Tchingal’s head in case I needed to stitch a few photos together to catch the emu’s full glory. As I did so, a bright fireball meteor plunged earthward between the Large and Small Magellanic Clouds. These neighbouring dwarf galaxies are 150,000 and 200,000 light years away respectively and consist of 15 billion and 5 billion suns. The Milky Way is 200 billion suns in mass.
A meteor passes between the Magellanic Clouds
To the right of the Southern Cross along the Milky Way is a small bright patch around a small yellowish star, Eta Carinae. It is the seventh brightest star in the constellation Carina, the keel of Jason’s ship Argo. This star is likely to be the largest star in the Milky Way, 150 times the mass of our sun and is 7500 light years away. The fuzzy glow around it is a vast cloud of dust and gas, lit by Eta Carinae and forming numerous clusters of new stars. Eta Carina is very unstable and underwent several convulsions in the 19th century, throwing off clouds of material that are easily seen through amateur telescopes.
Incomprehensible as Eta Carinae may be, the Tarantula Nebula in the Large Magellanic Cloud manages to dwarf it. To the right of the north end of the Cloud’s bar, it appears as a faint, fuzzy round glow to the naked eye under a dark sky. It is the largest star forming region in the Local Group of galaxies and have stars up to 300 times the mass of the sun and the nebula is 930 light years across.