Star's Erratic Conduct Hides Predictable Nature

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<b>Star's Erratic Conduct Hides Predictable Nature</b><br /><br />LINK<br /><br />A massive star known for violent and erratic behaviour shows a surprisingly predictable and regular pattern in brightness, reveals the most detailed study ever done on the star. But the clockwork signal has stumped astronomers, who hope to unravel how other such stars sow the universe with heavy elements. <br /><br />The object, called WR123, is one of 200 so-called "Wolf-Rayet" stars known in our galaxy. These represent a short-lived stage - lasting just a few hundred thousand years - in the lives of stars born with the mass of at least 25 Suns. <br /><br />Wolf-Rayet stars haemorrhage trillions of tonnes of material into space every second and are also thought to produce fleeting blasts of high-energy photons, called gamma-ray bursts, when they die as supernovae. <br /><br />The objects are "very important astrophysically", says Michael Corcoran, an astronomer with the Universities Space Research Association in Greenbelt, Maryland, US. "They produce the heavy elements we need for life - like carbon and oxygen - and they distribute them by blowing up."<br /><br />Explosive departures<br />But Wolf-Rayet stars are not well understood, and WR123 is a member of an even more mysterious subclass - called WN8 - whose 17 known members lie far from any stellar nursery. That suggests WN8 stars once had stellar companions that exploded as supernovae, which pushed the surviving stars into regions of empty space. The brightness of WN8 stars appears to vary chaotically.<br /><br />Indeed, previous ground-based observations showed WR123 dimmed and brightened on a number of different timescales - from once every 10 hours to once every few days. But the periodic signals tended to disappear after a short time, and observing runs were generally limited to evenings over a single week, providing limited statistics. <br /><br />Now, a team of ast