Runaway star is fleeing black hole

Astronomers from America and the UK have collaborated to identify the origin of a young star speeding away from the Milky Way at an incredible 1.6 million miles per hour.

They believe it is unique because it must have been fired like a bullet from a yet-undiscovered black hole in a small galaxy that orbits our own.

The runaway, labelled HE 0437-5439, is a hot, blue star nine times the mass of the Sun and around 35 million years old. We reported its discovery in 2005.

It covers 450 miles per second as it races through the cosmos. But unlike previous fast-moving stars, it is alien to our own Milky Way galaxy.

Astronomers Ian Hunter and Robert Ryans, from Queen’s University Belfast, closely studied the runaway star with colleagues from Carnegie, Washington.

They believe it once had a mate, being one of a pair of stars spinning around each other. But the stars ventured too close to a black hole 1,000 times the size of the sun.

As one star was pulled into the black hole, the other was whipped into a feenzy and flung out of the neighbouring galaxy, called the Large Magellanic Cloud. The astronomers say that nine previously found hypervelocity stars have all been ejected by a supermassive black hole at the centre of the Milky Way.

Alceste Bonanos, of Carnegie, said: “We’ve ruled out that the star came from the Milky Way. Like evidence from a crime scene, the fingerprints point to an origin in the Large Magellanic Cloud.”

He added: “This is the first observational clue that a massive black hole exists somewhere in the LMC. We look forward to finding out where this black hole might be.”

Artwork: Harvard-Smithsonian Center for Astrophysics

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