Monday 11 March 2019 — ASTROPHOTOGRAPHY
The brighter stars in each constellation are designated, roughly in order of their brightness, with a letter of the greek alphabet. this follows a system introduced by Johann Bayer (1572-1625). The brightest star in the constellation Centaurus (the Centaur) is Alpha Centauri, the nearest bright star to our sun. The 19th brightest “star” in that constellation is Omega Centauri.
Even with the naked eye, there is something slightly odd about this “star.” It appears to be slightly “fuzzy.” Looking at it with any telescope reveals one of the great wonders of the sky. Omega Centauri is in fact not one star, but around 10 million, gathered in the tight sphere of a globular cluster. This is the brightest and richest, as well as the largest and most massive, of these objects in the sky. Globular clusters are arranged as a “halo” outside the main arms and core of our galaxy, but closely linked with it. They are ancient, with stars formed in the first burst of the new Universe and lasting a very long time.
There have been suggestions (e.g. Young-Wook Lee and colleagues 1999) that the cluster is the remaining nucleus of a small galaxy that merged with our Milky Way. Another globular cluster (M54) appears to be the nucleus of a dwarf galaxy that is in the process of being absorbed by the Milky Way.
The constellation Centaurus is too far south to be visible from the British Isles. I have seen it, from a really dark site in Tanzania, and can say it is a stunning constellation with bright, beautifully coloured stars and close to the famous Southern Cross. Of course, the velvet dark and warmth of a tropical night helped with that impression!
This image is difficult to process. The bright core is so much brighter than the surrounding areas that I often found the object looking like a target or bullseye when I processed the image. This version is designed to show as much detail as possible, so has less contrast than the object would have if viewed through a telescope. Through a good telescope from a dark site, globular clusters are often “wow” objects that can take your breath away.
This is a 300mm f9 reflector sited in Bathurst, NSW, Australia, and fitted with a specialist camera for deep sky images. The colour image was made from 5 one-minute exposures each through clear (for luminance), red, green and blue filters. I processed it in PixInsight software integrating the separate images before bringng out the detail, colour and contrast in startools software.