Dr. Sarah Pearson

Astrophysicist, Science Communicator & Public Speaker

The Extragalactic Streams Group

Funded by Villum Fonden (project VIL53081) and by the European Commission (ERC starting grant: BeyondSTREAMS 101115754). The group's work focuses on what we can learn about the nature of dark matter from extragalactic streams through simulations, model-to-data comparisons, and observations from the Roman Space Telescope, Rubin, Euclid, and ARRAKIHS.

Sarah Pearson

group leader

Pearson recently returned to the Niels Bohr Institute at the University of Copenhagen after spending 10 years in the US, where she obtained her PhD degree in Astronomy from Columbia University in 2018, held a NASA Hubble Fellowship at New York University (2020-2023), and a Flatiron Research Fellowship at the Center for Computational Astrophysics (2018-2020). Pearson's research interests include galactic collisions, stellar streams, galactic bars, and dark matter. You can find a link to her publications here and details on her research interests here.

Khyati Malhan


Malhan's research interests include Galactic archaeology, dark matter, and he is best known for his work on the stellar streams of the Milky Way. His style encompasses and combines observations and data analysis (e.g., Gaia, APOGEE, LAMOST), running N-body simulations of stellar systems, and analyzing large-scale cosmological simulations (e.g., Illustris, TNG). He obtained his PhD from Strasbourg Observatory between 2015-18, followed by a postdoc at Stockholm University from 2018-21, and a Humboldt postdoc fellowship at MPIA, Heidelberg from 2021-23. You may find his publications here.

Sirui Wu

PhD student

Wu will join the group in September 2024 after obtaining his master's degree in astrophysics from Sun Yat-sen University in China. Wu's research interests focus on constraining dark matter distributions with various methods such as stellar streams, galaxy dynamical analysis, and gravitational lensing. He is also interested in the applications of machine learning in astronomical data analysis. You can find his most recent publications here.

Daniel A. Bobruk

Summer student

Daniel holds a Master’s degree from the Niels Bohr Institute specialized in astrophysics and high energy particle physics. He concluded his studies with a one year stay at CERN working with high energy charged particle interactions with Silicon crystals. Daniel has a strong passion for cosmology and galaxy dynamics. Before joining the group Daniel spent two years in a tech startup working with applied AI. His research will be focused on stellar streams as probes for examining dark matter distributions in galaxies.

Join our group!

The Extragalactic Streams group will be hiring more PhD students and postdocs in 2025 and 2026. In addition to positions in our group, there are also other opportunities to work at U. Copenhagen (e.g. the DAWN and DARK Postdoctoral Fellowships, and the Marie Skłodowska-Curie Actions fellowship, with a deadline on Sept. 11th, 2024). Please reach out if you are interested in working with us. For bachelor's or master's students enrolled at the University of Copenhagen, please get in contact about potential projects for the fall 2024 semester at sarah.pearson (at) nbi.ku.dk.

Prospective students can find the group research expectations here>>.