Free Astronomy Magazine May-June 2025

17 MAY-JUNE 2025 ASTRO PUBLISHING that can capture light from 5000 galaxies simultaneously. It was con- structed, and is operated, with fund- ing from the Department of Energy (DOE) Office of Science. DESI is mounted on the U.S. National Sci- observe roughly 40 million galaxies and quasars by the time the project ends. The DESI project is an international collaboration of more than 900 re- searchers from over 70 institutions around the world and is managed by DOE’s Lawrence Berkeley Na- tional Laboratory (Berkeley Lab). With DESI’s early data, which include survey validation and 20% of the first year of operations, the team, led by University of Utah postdoc- toral researcher Ragadeepika Pucha, was able to obtain an unprece- dented dataset that includes the spectra of 410,000 galaxies, includ- ing roughly 115,000 dwarf galaxies — small, diffuse galaxies containing thousands to several billions of stars and very little gas. This extensive set would allow Pucha and her team to explore the complex interplay between black hole evolution and dwarf galaxy evolution. While astrophysicists are fairly con- fident that all massive galaxies, like our Milky Way, host black holes at their centers, the picture becomes unclear as you move toward the low-mass end of the spectrum. Finding black holes is a challenge in itself, but identifying them in dwarf galaxies is even more difficult, owing to their small sizes and the limited ability of our current instru- ments to resolve the regions close to these objects. An actively feed- ing black hole, however, is easier to spot. “When a black hole at the center of a galaxy starts feeding, it unleashes a tremendous amount of energy into its surroundings, transforming into what we call an active galactic T his artist’s illustration depicts a dwarf galaxy that hosts an active galactic nucleus — an actively feed- ing black hole. In the background are many other dwarf galaxies hosting active black holes, as well as a variety of other types of galaxies hosting intermediate-mass black holes. [NOIRLab/NSF/AURA/J. da Silva/M. Zamani] ence Foundation (NSF) Nicholas U. Mayall 4-meter Telescope at the NSF Kitt Peak National Observatory, a Program of NSF NOIRLab. The pro- gram is now in its fourth of five years surveying the sky and is set to