Thursday, March 3, 2011
The Zone of Avoidance
When I was a kid, I couldn't wrap my head around the idea of the Milky Way. Once it was pointed out to me in the sky, on a dark clear night in a remote area, it was terrifying. It was like something out of a science fiction movie to discover that something so immense was taking up so much of the sky at night but you just don't notice it most of the time unless you really look. (And, of course, the more you look, the less you know.)
But even then, it took a long time as a child to really "get" the big picture, that we were part of the Milky Way galaxy, but out on the very fringes of it, looking sidelong at the edge of its spiral disc shape. And every star that we can see at night with the naked eye is also part of this galaxy. I feel sorry for the inhabitants of planets much deeper into the galaxy - they have no clear view of the night sky and their sense of astronomy is atrocious. On the other hand, their skies are freakin' gorgeous.
The Milky Way does throw a slight monkey wrench into our own astronomy, however - we have a very poor concept of what the Universe looks like on the other side of it. The Milky Way obstructs our view of about 20% of the sky at visible wavelengths, which is why optical surveys of the Universe are incomplete around the galactic plane. This area is known as the "Zone of avoidance", and remains one of the biggest (literally) mysteries in Science.
What little we know about the other side of the Milky Way has been gleaned from radio astronomy, but even then pickings have been slim. In 1995 an Australian project to survey the Zone via radio resulted in the discovery of The Dwingeloos, a pair of galaxies with one orbiting the other.
In 2003 a deep blind survey to map this uncharted portion of space was conducted as a joint effort between Universities in Mexico, New Mexico, and Australia. Analysis of the data revealed the presence of slightly over a thousand previously unknown galaxies. It also yielded a treasure trove of new information about little-understood places like the Norma Supercluster and the constantly-growing Local Void.
We know the Milky Way is moving in a specific direction, and it had previously been believed that it was being sucked toward something called The Great Attractor. But in 2005, the CIZA Project to explore the Zone via X-Rays, discovered that what is actually pulling us toward it is not the Great Attractor, but something even more powerful behind it: the Shapley Supercluster.
Even as the Shapley Supercluster is sucking everything within its sphere of influence toward it, the Local Void is expanding and pushing our "Local Sheet" of galaxies away from itself, at a rate of 600,000 miles per hour. From our own terrestrial perspective, Relativity prevents us from sensing the chaotic roller-coaster ride this section of the Universe - including our planet - is presently in.
Bill Hicks was right - life is just a ride. Enjoy it.