The fastest-moving stars in our galaxy may have been shot off the bow of a passing smaller galaxy.

Key points: Hypervelocity stars are the fastest stars in our galaxy

Scientists are not sure where they come from

Their clustering in one part of the sky could provide a clue

These so-called "galactic hypervelocity stars" are large and short-lived but travel up to 1,000 kilometres per second.

Strangely, most of them appear to be in an unusual cluster in the northern hemisphere sky, and the origin of these huge speedsters has been a bit of a puzzle.

But now, researchers from the University of Cambridge argue these stars may have been flung off the front of the Large Magellanic Cloud, a dwarf galaxy travelling at high speed past the edge of the Milky Way galaxy.

The findings of their new modelling study are published in the current Monthly Notices of the Royal Astronomical Society.

Puzzling origins of superfast stars

Hypervelocity stars are three to 10 times the mass of our Sun and are the fastest stars in our galaxy, travelling between 500km and 1,000km per second.

They are thought to form when one of a pair of massive stars orbiting each other explode in a supernova, and one of the partners is flung away at high speed.

Astronomers first thought these stellar sprinters, found on the edge of our galaxy, may have been sling-shotted there by the giant black hole at the centre of the Milky Way.

But these type of stars only last a few hundred million years and this would not be enough time for them to reach the speeds needed to travel so far out from our galaxy's centre.

"It's a bit of puzzle, because you'd expect really massive stars to be hard to accelerate up to these speeds," said PhD candidate Douglas Boubert, lead author of the new study.

This also doesn't solve the mystery of why galactic hypervelocity stars are mostly clustered in one part of the sky — in the constellations of Leo and Sextans.

The Large Magellanic Cloud is speeding past the Milky Way at 378 kilometres per second. ( Supplied: ESA/NASA/JPL-Caltech/STScI )

Mr Boubert and colleagues came up with the idea that perhaps the stars had come from the Large Magellanic Cloud, which is travelling past the outer edge of the Milky Way galaxy at 378km per second.

"Ejecting these stars from a dwarf galaxy, which itself is moving, is like putting that cannon on a train, because then the fastest stars are going to be the ones that are ejected in the same direction as the train's moving," he said.

When the researchers modelled what might happen if this scenario occurred with a star from the Large Magellanic Cloud, the results exactly matched what they could see in the sky.

Many more where they came from

The hypervelocity stars examined in the study were detected by the Sloan Digital Sky Survey, which only looks at a proportion of the northern hemisphere sky.

Mr Boubert suggested that this cluster could in fact be just the tip of a large trail of hypervelocity stars coming from the Large Magellanic Cloud.

The Gaia-ESA space observatory, launched in 2013, covers far more of the sky than the Sloan Digital Sky Survey, and is expected to deliver its first payload of data next year.

Mr Boubert hopes this will reveal more stars with the same direction and velocity as the cluster.

"I'm thinking they're at the very edge of this trail, the least dense part, so [this] implies that there are thousands more in the southern sky."