For the second time in history, we are very likely seeing an object crossing the Solar System region, but coming from the deep, extra-solar space. It is comet C/2019 Q4 Borisov: its eccentricity (at this very moment, the best eccentricity estimate is e = 3.2076692, that is a clearly hyperbolic – opened – orbit) and especially its speed when it approached the Solar System (about 30 km/s) suggests it is an interstellar comet.
About a week later, NASA and ESA astronomers obtained images of the object and performed several position measurements. The data confirmed the object’s unusual orbit, which was first reported by NASA’s Scout system.
“We can tell a lot about an object from the shape of its orbit, in particular its eccentricity — how much it is stretched,” explained Dr. Marco Micheli from ESA’s Near-Earth Object Coordination Centre and colleagues.