The star that astronomers call S301 isn’t your average ball of fiery plasma. For one thing, this newfound star is travelling at more than 8 per cent of the speed of light. Blink, and you’ll miss it.
But there is an even more striking thing about it: the simple fact that it shouldn’t exist. S301 isn’t an isolated oddity, either; it is the fastest-known member of a superhighway of stars frenetically circling the black hole at the centre of our galaxy. The extreme gravity in this region explains why the stars are zooming around so rapidly and why their very existence is unlikely.
Black holes usually rip apart the clouds of gas and dust from which stars form. But the fact that these stars do exist – and that we can now observe them – is extremely handy. The centre of our Milky Way galaxy is so bright and so crowded that, for decades, we could barely discern anything about what was going on there.
Today, thanks to S301 and its ilk, that is changing fast. The stars could reveal hidden properties of the black hole at the centre of our galaxy, expose what lurks around it and even test gravity in one of the universe’s most extreme places. The bombshell results that demand a new theory of the universe Earth is positioned in one of the Milky Way’s spiral arms, some 26,500 light years from the middle of the galaxy.
From where we are in the sleepy galactic suburbs, trying to look into the galactic centre is like squinting into the beam of a searchlight. The region is so crowded, and thus shines so brightly, that for most of astronomy’s history, there was little hope of picking out individual objects. Earth’s atmosphere blurs our view, making tiny objects especially difficult to resolve.
And the whole region is also shrouded in huge clouds of dust and gas. The central black hole, called Sagittarius A*, wasn’t discovered until 1974, just a few decades after astronomers concluded that its neighbourhood was, in fact, the centre of the Milky Way. Only recently have astronomers been able to see through this mess well enough to pick out individual stars.
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