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© NASA/JPL-Caltech/GLIMPSE Team/M Rahman/U of Toronto
Dragonfish are fearsome deep-sea predators with giant mouths, bulging eyes and a propensity for eating bioluminescent prey. Now it seems they have a celestial counterpart in the Dragonfish nebula. Hidden in its gaping maw may be the Milky Way's most massive cluster of young stars.

Mubdi Rahman and Norman Murray, both of the University of Toronto in Canada, found the first hint of the cluster in 2010 in the form of a big cloud of ionised gas 30,000 light years from Earth. They picked up the gas by its microwave emissions - suspecting that radiation from massive stars nearby had ionised the gas.

Now Rahman and his colleagues have identified a knot of 400 massive stars in the cloud's heart in images from the infrared 2 Micron All Sky Survey (Astrophysical Journal Letters, in press). The cluster probably contains many more stars too small and dim to see.

The surrounding cloud of ionised gas is producing more microwaves than clouds around other star clusters in our galaxy. That suggests the Dragonfish is the brightest and most massive young cluster discovered so far, with a total mass in the range of 100,000 times the mass of the sun.

"Until now, we've only seen clusters this size outside of our galaxy," Rahman says. Because it is so much closer, it can be studied in greater detail, he says.