How much power is released when half of a binary system explodes? Would you believe it’s enough power to launch the other star straight out of the galaxy at 2.7 million miles per hour? That, according to researchers, is what happened to US 708, an unbound star that is on a trajectory to eventually leave the Milky Way galaxy altogether and roam space on its own.

An unbound star, is a body that has encountered a force strong enough to dislodge it from the gravitational pull of the galaxy and send it on a different trajectory. Usually that force is a black hole. All of the known unbound stars, with the exception of US 708, are believed to have gotten too close to the black hole at the center of the milky way. However, the trajectory and speed of this star don’t match the profile for that.

“Imagine you go to a fair and ride a carousel, and the carousel goes round and round, and then the carousel explodes. What happens to you? You go flying away because your seat has such high velocity,” said Stephan Geier to the New York Times.

Geier is an astronomer at the European Southern Observatory (ESO) and lead author of the study which appears in the journal Science.

The researchers determined the velocity and trajectory of the star by observing it with the the W. M. Keck Observatory and Pan-STARRS1 telescopes in Hawaii and combining modern observations with archival measurements.

They noted that US 708 was unusual when compared with other hypervelocity stars. It is a compact, sub-dwarf, helium star that is rotating very rapidly. Because of this they believe that it was likely formed as part of a binary star system with a white dwarf that exploded in a Type 1a supernova. When its companion exploded US 708 was launched toward the outer edges of the galaxy.

“These results provide observational evidence of a link between helium stars and thermonuclear supernovae, and is a step towards understanding the progenitor systems of these mysterious explosions,” according to a statement.

According to Geier, the stars companion white dwarf would have started by stealing all of its hydrogen until all that was left was helium. The white dwarf would have then begun taking helium from the sub-dwarf until it destabilized and exploded. He believes that it was not the explosion itself, but the release that sent US 708 flying.

“It’s not a shockwave, it’s the mere fact that this star is unleashed from this very tight binary,” says Geier told New Scientist.

If the researchers are correct, finding more stars like US 708 could provide a way to study supernova. If, as scientists believe, the supernovae all happen in the same way then these could provide new “standard candles”.

Standard candles act as a “cosmic ruler”, allowing astronomers to measure distances in the vast universe.

“If we can really prove this scenario, then we have a means to study those explosions in a new and very interesting way,” says Geier.