Stellar streams, the tidally-disrupted remnants of globular clusters and dwarf galaxies orbiting throughout the Milky Way's halo, are some of the most powerful tools for mapping dark matter across cosmic scales. They are sensitive probes of dark matter structure from the smallest subhalos, below the threshold of galaxy formation, to the Milky Way’s own dark matter halo, as well as excellent tracers of the growth and assembly of our Galaxy. Thanks to recent large photometric, astrometric, and spectroscopic surveys, the population of stellar streams around the Milky Way is finally being revealed. In this talk, I will present the discovery, characterization, and modeling of Milky Way stellar streams. I will also present the first comparative studies of stream populations in observations and cosmological simulations, which have revealed inconsistencies in orbital parameters and disruption rates, as well as a wealth of potentially yet-to-be-detected stellar streams. Finally, I will present plans to use upcoming surveys, including the Rubin Observatory LSST and the Roman Space Telescope, to discover and characterize tidal structures throughout the Milky Way halo, enabling powerful stream-based population-level constraints on the dark matter subhalo mass function and the particle nature of dark matter.

Speaker: Nora Shipp (University of Washington)

The 2026 Spring Colloquium talks are held on Wednesdays at 3:00 PM. This colloquium is hosted by STScI and will be held as an in-person and virtual event.

You may join in person at STScI’s John N. Bahcall Auditorium or virtually on the STScI Research YouTube channel.

Please direct questions or comments to contact above. The 2026 Spring Colloquium members are: Nimisha Kumari (STScI), Elena Manjavacas (STScI), Jack Neustadt (JHU), Kevin Schlaufman (JHU), Adam Smercina (STScI), Ethan Vishniac (JHU).