Astronomers have confirmed the existence of thousands of planets outside of our own solar system (called extrasolar planets or exoplanets) orbiting nearby stars like our Sun in our own Galaxy. Many of the systems are completely unlike our own solar system though, and our improved understanding of how planets form has been greatly influenced by the new discoveries. Most of the differences between our own solar system and the known exoplanets are due to the fact that the ways that we find exoplanets are not perfect -- they're much, much better at finding massive planets like Jupiter that are closer to their host stars than Earth is to the Sun, and much, much worse at finding planets like Earth. Still, there is enormous diversity in the exoplanet population of our Galaxy, and a general theory of planet formation should explain them all.
I'm playing a small role in the effort to better understand the properties of the exoplanet population and to use those properties to improve our understanding of planet formation. My research has been featured in Science Magazine and on the web at Wired, New Scientist, Science Now, Astrobio.net, and the popular exoplanet blog Oklo (here, here, and here).
Like all other upper middle-class galaxies, our own Milky Way Galaxy has been built-up through the acquisition of more stuff: more gas, more stars, and more dark matter. Some of the gas and the dark matter continuously stream into our own Galaxy from the space between galaxies -- this is not the case for the stars though, as stars can only form in galaxies. Now, most of the stars in our own Galaxy are natives that formed here; however, there is a population of stars that have compositions and orbits seemingly unlike the stars native to our own Galaxy. These stars potentially formed in smaller galaxies that our Galaxy has gravitational acquired and torn asunder over the past 10 billion years. At the same time, they might also be very atypical stars that are nevertheless native to the Milky Way. Either way, they're valuable finds that can provide insight into the formation of our Galaxy and into the characteristics of the universe billions of years ago in a way that no other population of stars can. Unfortunately, trying to find rare stars like these in our Galaxy is like trying to find needles in a haystack.
Even though these special stars are hard to find, there is hope. Certain special properties of the way that the orbits of stars change over time due to the mutual gravitational interactions between those stars can cause the special stars to stand out. Once they're identified as such, further study of those special stars can reveal a lot about the environments in which they formed.
For my PhD dissertation, I found some of those special stars. The properties of the stars allowed me to figure out what type of galaxy they came from, even though that galaxy was eaten by our own Milky Way 5 billion years ago! I'm currently working to find the most ancient stars in the Galaxy that are currently closest to the Sun. Ancient stars are typically found far away from the Sun in the outskirts of the Galaxy, so it's import to find them in the vicinity of the Sun so that we can study them in detail.