A runaway black hole is tearing through the universe, leaving a trail of stars in its wake that's never been seen before, NASA says.

The supermassive black hole weighs as much as 20 million suns - and it's travelling so fast that if it were in our solar system, it could travel from Earth to the Moon in 14 minutes.

It has left behind a 200,000 light year long trail of newborn stars, twice the diameter of our Milky Way galaxy.

The phenomenon was accidentally spotted through NASA's Hubble Telescope, with the astronomer who discovered it saying the sighting was "pure serendipity".

"It didn't look like anything we've seen before," said Pieter van Dokkum of Yale University.

The star trail was "quite astonishing, very, very bright and very unusual", he said, describing it as like the wake of a ship.

This led to the conclusion that he was looking at the aftermath of a black hole flying through a halo of gas surrounding the host galaxy.

The stars are being created when the black hole ploughs into the gas in front of it, researchers believe.

The supermassive black hole is likely the result of three black holes colliding. Scientists believe two of the black holes merged perhaps 50 million years ago before another galaxy joined with its own black hole.

One of the black holes was then thrown out of its host galaxy, with one black hole shooting off in one direction and the other two travelling in the opposite direction.

Scientists will make follow-up observations to confirm this explanation.

The team's research was published on Thursday in the Astrophysical Journal Letters.