The Mopra Telescope, at Coonabarabran, NSW

2004 saw the first operations of ‘on-the-fly’ mapping with the Mopra radiotelescope. Until recently, the main mode of operation of Mopra has been a simple point and shoot method, giving you one spectrum each time you point the telescope. To fully understand astrophysical phenomena, it is essential to know how dust and gas is distributed in the sky, not just what it is doing at one point in the sky. Therefore mapping is a very useful part of astrophysics. The new method of ‘on-the-fly’ mapping has greatly increased the efficiency of the telescope.

I have used this method to observe one interesting region of massive star formation within our Galaxy. The observations were made during October 2004 when the weather was not good enough for our main observing project. The region contains two distinct centres of massive star formation that show starkly different qualities: one appears to be well developed and is associated with a very bright infrared source, the other has no infrared counterpart whatsoever – presumably because it is at such an early phase of evolution that the protostar has no had the chance to heat up its surroundings yet. With no infrared counterpart, this second younger source has been something of a mystery until the recent Mopra observations. The maps show that a whole host of complex molecules – the signatures of star formation – are associated with the younger source and not the older source. ¹³CO (an isotope of carbon monoxide), HCO⁺ (hydrogenated carbon monoxide), N₂H⁺ (diazenylium), CH₃CN (methyl cyanide) and even CH₃OH (methanol) are detected here, confirming that this source is one of the youngest sites of massive star formation known.

Andrew Walsh