Queen’s University astronomy professor Martin Duncan, and an international team of astronomers, have discovered that many of the comets observed from Earth – including well known comets like Halley, Hale-Bopp and McNaught – may have been formed in orbit around other stars and not our own sun.
Using computer simulations, researchers demonstrate that the Sun may have captured small icy bodies from its sibling stars while still in its birth star cluster, creating a reservoir of observed comets.
Although the Sun has no companion stars now, it is believed to have formed in a cluster of hundreds of closely packed stars all embedded in a dense cloud of gas. During this time, each star formed a large number of small icy bodies – which is what comets are composed of – in a disk from which planets formed.
Most of these comets were flung out of these early planetary systems by the newly forming giant planets, becoming tiny, free-floating entities in the cluster.
Our sun’s cluster was destroyed when its gas was blown out by the hottest young stars. The researchers’ computer models indicate that the Sun then gravitationally captured a large cloud of comets as the cluster dispersed.
“Anyone who has seen a long tail comet in the night sky may be looking at material from another star,” says Professor Duncan.
“The process of capture is surprisingly efficient and leads to the exciting possibility that the cloud contains a potpourri which samples material from a large number of stellar siblings of the Sun.”
Evidence for the team’s hypothesis is indicated in the roughly spherical cloud of comets – called the “Oort cloud” – surrounding the Sun. Exactly how the Oort cloud was created has been a mystery for more than 60 years.
“We have a new model of how the Oort cloud formed. We’re not the first to suggest this could happen but we are the first to show it in a detailed computer simulation,” adds Professor Duncan.
Photo: Chris (chrs_snll)