Mapping the Milky Way
How big is the Milky Way galaxy? How fast does it rotate? Where, in its vast expanses, is our sun located?
When you're right in the middle of something, it's hard to get the big picture. Such the case with our own Milky Way, which astronomers can only observe from within. Based on radio astronomical investigations of the distribution of hydrogen clouds, we do know that the Milky Way is a rotating disc-shaped gathering of stars, gas and dust about 100,000 light-years across and 1,000 light-years thick. Our sun is located along one of the Milky Way's spiral arms, but its exact distance from the center of the galaxy is unknown.
SIM PlanetQuest will use optical interferometry to measure the distances between stars throughout the galaxy with unprecedented accuracy. Interferometry is the process of combining light from two or more telescopes as if they were pieces of a single, gigantic telescope mirror.
With its precise measuring ability, SIM PlanetQuest will allow astronomers to create a new, more accurate roadmap of our home galaxy, and answer many fundamental questions about it size, shape and structure.