It is orbiting a star called Gliese 876, 15 light years from Earth, with an orbit time of just 1.94 Earth days.

They found that the shuttle's orbit time could be extended by 25 days, and reckoned that, with a second shuttle on stand-by in case crew needed rescuing, the risk was acceptable.

The shape of this orbit isn't consistent; it varies over time, over a period of about a thousand years.