Astronomers say they have discovered a star cluster that has been thrown in the direction of Earth at a speed of more than two million miles per hour.

The cluster, named HVGC-1, originated in the M87 galaxy and is expected to endlessly drift through space, rocketing through the voids between other galaxies.

"Astronomers have found runaway stars before, but this is the first time we've found a runaway star cluster," said Nelson Caldwell of the Harvard-Smithsonian Center for Astrophysics, who is the lead author on a study which is set to be published in the The Astrophysical Journal.

HVGC stands for hypervelocity globular cluster. These clusters are groupings of thousands of stars contained inside a ball a few dozen light-years across.

The team found HVGC-1 using the MMT Telescope in Arizona after spending years studying the space around M87. A computer then calculated the speed of the cluster.

"We didn't expect to find anything moving that fast," said Jay Strader of Michigan State University, who is a co-author of the study.

The Milky Way Galaxy holds around 150 globular clusters, while the M87 galaxy holds thousands, according to a news release from Harvard-Smithsonian Center for Astrophysics.

Astronomers believe HVGC-1 could have reached its current speed after passing through two supermassive black holes at the center of M87, which acted like a slingshot, flinging the cluster away.