Daniel Weisz, an assistant professor of astronomy at UC Berkeley, was honored at this week’s meeting of the American Astronomical Society for his early-career research on relatively nearby “dwarf” galaxies using the Hubble Space Telescope.

He received the 2019 Newton Lacy Pierce Prize “for his transformational work on the star-formation histories of dwarf galaxies in the Local Group, our galactic neighborhood.”

Weisz came to UC Berkeley in the summer of 2016 and focuses on stars, dark matter, and galaxies near Earth, in particular the Local Group of galaxies that includes some 100 mostly small galaxies surrounding the two heavies, our own Milky Way and Andromeda.

While obtaining his Ph.D. in astrophysics from the University of Minnesota in 2010 and during subsequent fellowships, including a Hubble Fellowship, at the University of Washington and UC Santa Cruz, he worked with Hubble observations to resolve individual stars within the dwarf galaxies in the Local Group so as to determine their brightness and temperature.

“The temperatures and luminosities of stars encode their age,” he said. “By counting up all the stars of different ages in a galaxy, it’s possible to reconstruct a galaxy’s star-formation history — that is, how many stars formed at a given time — over the entire history of the universe.”

In the past, star-formation histories in the Local Group have been measured one galaxy at a time, often using different analysis techniques. But in 2014, Weisz published a paper with measurements of the star-formation histories of 40 dwarf galaxies in the Local Group, all using the same analysis technique on existing Hubble data.

This allowed him to look for statistical trends in the data. He subsequently documented when in their history these Local Group dwarf galaxies stopped making stars, or “quenched,” and how this was affected by the proximity of the larger galaxies, including the Milky Way.

He is looking forward to taking the first observations of the local universe with the James Webb Space Telescope, the successor to Hubble that is scheduled for launch in 2021.