There are around a hundred billion stars in the Milky Way, and most are rather humdrum – but the oddballs are so strange that they challenge our understanding of physics

Renaud Vigourt

WITH hundreds of billions of stars in our galaxy alone, you would expect a few oddballs – and you would be right. Stars do follow a more or less set life path, determined by their mass. But we are increasingly finding that the details of those lives can diverge more than we ever imagined. In some cases, we are discovering stellar characteristics and habits so outlandish that they challenge our understanding of physics.

From a cannibalistic star to one that makes impossible elements and another that refuses to die, here is our introduction to some of the strangest stars in the universe.

The one that got away

Our galaxy is leaking stars. That is the only conclusion astronomers have been able to draw from the discovery of a few dozen stars travelling so fast that not even the gravity of the Milky Way can hold on to them. The record holder is S5-HVS1, which clocks in at 1700 kilometres per second – so fast that it has already broken out into the lonely reaches of intergalactic space. But how has an enormous ball of gas accelerated to such a speed?

When Warren Brown at the Harvard-Smithsonian Center for Astrophysics identified the first hypervelocity star in 2005, it appeared to have come from the centre of the galaxy. That pointed the finger at the supermassive black hole there. Brown’s calculations showed that if a pair of stars passed close enough, the black hole would snatch hold of one of them and shoot the other off into space.