Five enigmatic stars in a cluster at the heart of the Milky Way have each turned out to be mammoth young double star systems, trailing dust into elegant pinwheel shapes as they live fast and die young.
The Quintuplet, discovered in 1990, is a cluster of hundreds of stars around 26,000 light years away, near our Galaxy’s centre. It takes its name from five prominent red stars cocooned in dust, which have puzzled astronomers.
Starlight normally has sharp lumps and bumps at different wavelengths that characterise a star’s composition, age and size. But the five Quintuplet stars emit curiously uniform, featureless light across a wide waveband.
“When we use our regular barrage of observations that we throw at most stars, we come up with no answers,” says Donald Figer from the Rochester Institute of Technology in New York state, US.
Now Figer and his colleagues, led by Peter Tuthill from the University of Sydney in Australia, have revealed that all we are seeing is the dust around five double star systems, which produces the illusion of five single stars.
They used one of the twin 10-metre Keck telescopes on Mauna Kea, Hawaii, to create infrared images of the five Quintuplet stars in unprecedented detail. At least two revealed dust lanes in a clear spiral shape.
Figer believes the spirals are created by pairs of stars, each containing a so-called “Wolf-Rayet star” with a violent wind blowing outwards at about 2000 kilometres per second. Such stars represent a short-lived stage in the lives of stars born with the mass of at least 25 Suns.
The fast wind of the Wolf-Rayet star crashes into that of the stellar giant orbiting around it. Dense, cool dust forms in the region where the two winds collide, and this carves out a spiral as the two stars circle each other. “You have an effect like a garden hose being twirled around,” Figer told New Scientist.
If the stars in the Quintuplet are indeed Wolf-Rayet types, the finding should shed light on this fleeting life-stage – the stars will soon (relatively speaking) blow themselves to smithereens.
“It’s the last stage before they go supernova, probably within a few hundred thousand years,” says Figer.
Journal reference: Science (vol 313, p 935)
