Astronomers have a good grasp of how stars such as our Sun form from clouds of gas and dust, but how heavier stars form is still largely unknown.
"Massive stars are rare, making up only a few per cent of all stars, and they will only form in significant numbers when really massive clouds of gas collapse, creating hundreds of stars of different masses," said Dr Peter Barnes from the University of Florida. "Smaller gas clouds are not likely to make big stars."
The massive star-forming region BYF73 seen in near-infrared light at a wavelength of 2.25 micrometres, imaged with the IRIS2 camera on the Anglo-Australian Telescope in eastern Australia.
(photo credit: AAO)
Accordingly, regions in space where massive stars seem to be forming are also rare. Most are well over 1000 light-years away, making them hard to observe.
Using CSIRO's 'Mopra' radio telescope – a 22m dish near Coonabarabran, NSW – the research team discovered the massive cloud of mostly hydrogen gas and dust, three or more light-years across, that is collapsing in on itself and will probably form a huge cluster of stars. The discovery was made during a survey of more than 200 gas clouds.
BYF73 is about 8,000 light years away, in the constellation of Carina ("the keel") in the Southern sky. Evidence for 'infalling' gas came from the radio telescope's detection of two kinds of molecules in the cloud – HCO+ and H13CO+. The spectral lines from the HCO+ molecules in particular showed the gas had a velocity and temperature pattern that indicated collapse.
The CSIRO telescope observations were confirmed by observations with the Atacama Submillimeter Telescope Experiment (ATSE) telescope in Chile. The research team calculates that the gas is falling in at the rate of about three per cent of the Sun's mass every year – one of the highest rates known.
Follow-up infrared observations made with the 3.9-m Anglo-Australian Telescope (also near Coonabarabran, NSW) showed signs of massive young stars that have already formed right at the centre of the gas clump, and new stars forming.
Star-formation in the cloud was also evident in archival data from the Spitzer and MSX spacecraft, which observe in the mid-infrared.