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Space

Some of the fastest stars in the Milky Way come from other galaxies

Extreme-velocity stars, which travel through the Milky Way with speeds of hundreds of kilometres per second, may come from dwarf galaxies that our own galaxy gobbled up

By Leah Crane

8 April 2022

Illustration of the Milky Way galaxy as it might appear edge on. The Milky Way is a barred spiral galaxy roughly 100000 light-years in diameter. It is flat, shaped like two fried eggs back-to-back. At the centre is the nucleus, a vast flattened ball of old, red stars orbiting a supermassive black hole. This view imagines our galaxy seen from far from its nucleus, within the galactic plane. A lane of dust bisects the galaxy. Globular clusters (spherical clusters of stars) orbit here. One is seen in close up on the lower right.

Illustration of the Milky Way

Mark Garlick/Science Photo Library/Getty Images

The speediest stars in the galaxy, moving at hundreds or even thousands of kilometres per second, are also some of the least well-studied. A study of 15 of these fast-moving objects has found that most of them probably came from dwarf galaxies devoured by the Milky Way in the distant past.

“Some stars that are travelling fast have been [proposed to have] an extragalactic origin, but this is the first time that a relatively large sample has been analysed and evidence has been shown that they …

Article amended on 8 April 2022

We corrected the speeds of the stars.

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