Front Cover – The Tarantula Nebula in the Large Magellanic Cloud
The two Magellanic Clouds are in fact both irregular dwarf galaxies that – probably – orbit the Milky Way. These galaxies are both visible to the naked eye from much of the southern hemisphere – light pollution notwithstanding – and they owe their names to Ferdinand Magellan who documented seeing them in his voyage of 1519. As with much of our universe, ongoing astronomical studies of this region of space continue to turn up new information. As recently as November 2021, a black hole was discovered within the Large Magellanic Cloud. And data collected from the Hubble Space Telescope appears to indicate that these galaxies are moving too quickly to be orbiting the Milky Way.
For the present at least, the Large Magellanic Cloud can be found within the constellation Dorado, situated close enough the the southern celestial pole that from some latitudes, the LMC can be seen all year round. Neither of these galaxies are really observable from the northern hemisphere.
January – The Lagoon Nebula
The Lagoon Nebula is estimated at between 4,000 – 6,000 lightyears away, near the centre of the Milky Way in the Sagittarius star cloud. At its centre lies an open star cluster, NGC6530. Within its gaseous clouds there is also a very hot O-type star, which is responsible for ionising the particles visible in the nebula, causing them to emit the light that is captured here.
The Lagoon Nebula is a Hydrogen-rich molecular complex, and appears pinky-red in regular (RGB) photographs. As with most nebulae, it appears as a grey or colourless cloud to the human eye, thanks to the evolutionary prioritisation of detecting movement above colour in human night vision. This rendering of the nebula is a false colour, narrowband image. Narrowband imaging uses light filters to restrict the wavelengths of light being recorded by the camera sensor to very specific frequencies – in this case, the light emitted by Hydrogen Alpha, Oxygen III, and Sulphur II ionised gas particles. Having captured these three different wavelengths of light, colours are assigned to each gas that, rather than displaying the “true” or natural colour of each particle, instead allocates red to the sulphur data, and green to the (otherwise quite overpowering) hydrogen data, in a colour palette made famous by the images released by the Hubble Telescope. This Hubble Palette, or variations of it, are my preferred palette for exposing details of emissions nebulae, especially the dark tendrils of Bok Globules that stand out in contrast to the paler background rendering of the heart of the nebula.
February – Horsehead & Flame Nebulae
The constellation of Orion is an absolute favourite for astrophotographers. It is a rich and dense molecular complex that is easily recognised in the summer night sky here in the southern hemisphere. Indeed Orion is probably more popular in the northern hemisphere where their long winter nights can provide 12 or more hours of dark skies, provided the weather decides to cooperate!
The Horsehead Nebula is 1,375 lightyears from earth, and is a dark nebula that is dramatically backlit by the bright star-forming region behind it. Similarly, the Flame Nebula (the maple-leaf shaped structure to the left of the Horsehead) is a conglomeration of dark nebulosity matter, set in front of the glowing clouds of ionised Hydrogen being bombarded with energy from Alnitak.
March – The Statue of Liberty Nebula
Another target only visible in the southern hemisphere, the Statue of Liberty nebula bears the hallmarks of a star-forming region (or stellar nursery) – lots of ionised HII, and distinctive nebulous structures shaped by the incredible solar winds from new, very hot, very large stars that have formed from the available molecular material.
This nebula is 100 light years across, meaning that a photon emitted at one end of the nebula would take 100 earth years to reach the other end, travelling at the speed of light.
April – The Southern Pinwheel Galaxy
The only galaxy in this year’s collection, the Southern Pinwheel Galaxy was first discovered in 1752. Charles Messier added it to his record of nebulous objects in 1781, and as the 83rd object he catalogued it is most commonly referred to as Messier 83, or just M83. It is one of the brightest galaxies in the night sky, and can be seen through binoculars, most easily in the month of May. Six supernovae have been identified within this galaxy, and it has active star formation along the outer reaches of its spiral arms.
May – The Omega Nebula
June – The Gabriela Mistral Nebula
July – The Eagle Nebula
August – Carina Nebula
September – The Small Magellanic Cloud
October – The Fighting Dragons or Ara
November – The Greater Carina Nebula Complex
December – The Rosette Nebula
