June 11, 2010


Behold! Thy ExoComet Cometh!
Just a day after I posted an entry about Comet McNaught and showed how "otherworldy" it seems to me, along comes an article that says that maybe 90% of comets lurking in the outer parts of our solar system are from other planetary systems!
I'm tempted to call them "exoComets" even if they're already part of our solar system, because some famous comets such as Halley, Hale-Bopp and McNaught might have originated from around other stars!
Wait! How did that happen? The nearest star is Proxima Centauri, which is 4.2 light-years away. Surely it would take thousands of years for an interstellar comet to travel to our solar system!
Well, here's the reason why some of these comets may be "exo": Stars often form in clusters. And perhaps a long long time ago, our Sun may have shared comets with her stellar "sisters" who may have been quite nearer at that time. When you think about it, our Oort cloud which is estimated to have around 400 billion comets, is spread so far and wide past Pluto that its already a quarter of the distance to Proxima Centauri (but some estimates say that the spherical Oort cloud extends up to 3 light-years from our sun!).
Computer simulations reveal that perhaps the green Comet McNaught featured in my previous post may have had a long history that ties it with other stars in the distant past.
Hey, you never know, these pretty comets might be messengers from Alpha Centauri!