Robyn Sanderson

Weighing and measuring the Milky Way and other galaxies
Contact information:
Columbia University Department of Astronomy
Mail Code 5246
550 W 120th St
New York, NY 10027
Fellowship status:
Starting year: 2014
Research Interests:

Outside the Galactic disk, where most stars including our Sun reside, most of our Galaxy's mass is in its roughly spherical halo of dark matter, invisible material only known to exist through its gravitational influence. Also out there are a handful of halo stars, including the scattered remains of smaller galaxies that entered the Milky Way's dark halo only to be ripped apart by its tidal forces. Even after one of these small galaxies is destroyed, its stars follow similar paths as they orbit the Milky Way since they were neighbors to begin with. The small differences in the stars' orbits spread them out over time into a long trail of stars called a tidal stream.

In my research, I develop and use new tools to explore the structure of dark matter halos, particularly the Milky Way's, by studying their tidal streams. `The common origin of tidal stream stars gives us insight into the Galaxy's mass distribution, which determines their orbits: only if we guess close to the true mass distribution do the predicted orbits of stars in each stream stay lined up. Changes to the neighboring orbits of tidal stream stars could also provide evidence for smaller-scale dark matter structure: tiny dark matter clumps too small to hold galaxies, predicted by some theories of dark matter, would deflect the paths of stream stars in predictable ways. I hope to use the information from the new tools I develop to compare the structures of galaxy halos to the predictions of different theories of dark matter.

Education and Outreach Interests:

My research might use cutting-edge methods, but it is based on fundamental concepts that kids learn in middle school: why stars shine, how we make and read maps, and how gravity works. To teach these core ideas and inspire middle schoolers' interest in science, I am developing portable science lessons for use in underserved New York City middle schools. These multimedia lessons will incorporate the images and movies I produce in my research, remixed with songs and movement the students produce themselves to introduce them to the "music of the spheres."