Armageddon: scientists calculate how stars can nudge comets to strike Earth

Plotting how often stars stray into the Oort cloud allows astronomers to assess the risk of all life being wiped out by a cosmic cataclysm

The collision of a giant comet with the Earth is one of the most violent and cataclysmic events that could befall our planet. It has happened in the past, but the odds of another such catastrophe have remained uncertain.

Now astronomers have performed the cosmic equivalent of a risk assessment. A new paper calculates how often stars stray into the Oort cloud, a vast, spherical shell of billions of icy objects that is thought to envelop our solar system. Such close encounters can dislodge these loosely orbiting comets, sending them hurtling into the solar system, risking a collision course with the Earth.