Solar system 'bounce' may send comets our way
19 April 2008
Ker Than
Magazine issue 2652
OUR solar system has a bounce in its step, which may regularly send streams of comets hurtling into the Earth's neighbourhood.
The solar system orbits the Milky Way's centre, but it does not travel exactly on the galactic plane. As a result, the gravity of the plane pulls the solar system towards it, through it, and back again at regular intervals - we pass through the plane every 35 to 40 million years.
William Napier and Janaki Wickramasinghe at Cardiff University, UK, built a computer model of this motion. They found that when the oscillation brings us closer to the galactic plane, its gravitational tug can perturb comets in the Oort cloud, which surrounds the solar system. Similarly, passing through the galactic plane may bring the solar system into collision with the massive gas nebulas that reside there, which can also dislodge comets.