Expert: Courtney Seligman - 4/16/2009

Question
Goodmorning from Barcelona. After recently watching 2012 Nostradamus on the History Channel -which contained a lot of speculation interlaced with astronomical probabilities- i was left curious. How do we know where we are positioned in our Milky Way, and how do we know its exact form, when we are actually in it?

Answer
Although visible light cannot penetrate the clouds of gas and dust which lie in the plane of the Galaxy, other wavelengths of electromagnetic radiation can be used to map the direction and motions of stars and gases which lie beyond our 'local' view. In addition some objects, such as globular clusters, lie above or below the plane of the galaxy, and can be directly studied at all wavelengths. A comparison of the results of these measurements with direct observation of other galaxies allows us to create models of our Galaxy.

Prior to the start of the space age, such models weren't nearly as accurate, because our atmosphere blocks many of the wavelengths which are used to study the Galaxy. But now that we have several large telescopes in space, each studying a different wavelength region, we have fairly detailed knowledge of where we are, and what lies around us.