Whenever I talk about my astronomy research, I realize that for most people, the fascination begins with star-gazing. I can't say that I know much about the constellations (I do recognize the Big Dipper and Orion, and that’s about it) but it is a constant reminder of how little most people know what they are missing with the naked eye.
To really understand where our small planet fits in, it’s helpful to look at the hierarchy of systems that are found in the universe. I think of this hierarchy in terms of size, running from small to enormous collections of objects. On the small end are solar systems, where a series of planets orbits around a central star. Galaxies like the Milky Way define the mid-range. Galaxy clusters, which are collections of thousands of galaxies, are the largest in this hierarchy.
The solar system everyone recognizes is our own, with nine... I mean eight... planets orbiting around the Sun. When I was in elementary school, they taught us “My Very Eager Mother Just Served Us Nine Pickles” as a reminder of the planets in our solar system. With the recent demotion of Pluto, I guess it's now "My Very Eager Mother Just Served Us Nachos".
Well, it turns out that we are not alone, or at least our solar system is not alone. There are now over 200 known solar systems in the Milky Way. These solar systems are very hard to find, since the planets that make the system do not emit light or "shine." Typically, these solar systems are identified through very careful observations of the central star. A central star, analogous to the Sun, displays a subtle wiggle or change in brightness with the passing of large planets in its system. These planets are known as extrasolar planets.
One person in the Bay Area community who is making serious headway in this research is Geoff Marcy at UC-Berkeley as part of the California and Carnegie Planet Search. Their team has discovered more than 100 extrasolar planets around nearby stars. No one really knows how many of these planets are out there. For all we know, every sun-sized star has its own solar system. It’s just going to take some time to find them all.