Punted by the explosion of a massive white dwarf star that was once its neighbor in a shared solar system, the star known as US 708 is traveling at unprecedented speed on a one-way trip out of the Milky Way, according to data gathered by the Pan-STARRS1 telescope on Maui.
Unencumbered by gravity, the "unbound" US 708 is traveling at an estimated rate of 745 miles per second, the fastest speed ever recorded for an object within the Milky Way.
There are only six other known stars moving at sufficient velocity to allow them to escape the galaxy.
Stars, including our sun, are bound to the galaxy by gravity and orbit its center at moderate velocities. Scientists have theorized that it would take something as powerful as a thermonuclear supernova explosion to propel a star fast enough to break the bonds of galactic gravity.
That, according to a team of scientists led by Stephan Geier of the European Southern Observatory, is likely what happened to US 708. The team includes astronomers from Queen’s University Belfast in Northern Ireland.
According to the researchers, US 708 was likely one of two stars in a double-star solar system.
Drawing helium from US 708, the other star, a massive white dwarf, eventually exploded, violently ejecting US 708 from the system.
The team used the Echellette Spectrograph and Imager on the Keck II telescope to determine exactly how fast the US 708 is moving away. They then combined position measurements from digital archives dating back nearly 60 years with newer positions measured from images taken with the Pan-STARRS1 telescope to determine how fast the star is moving perpendicular to Earth.
That information allowed the team to "make a movie of the motions of the stars in the sky," according to team member Eugene Magnier, an astronomer with the University of Hawaii at Manoa.
