The collaboration’s first meeting at BU demonstrates how convergent research can advance the search for answers about dark energy.
In July, the 17th floor of the Duan Family Center for Computing and Data Sciences filled with 120 cosmologists, data scientists, and more. Soon, the quiet hum of introductions over coffee expanded into thoughtful conversations about the fundamental physics of the universe. It was the first time the Dark Energy Science Collaboration (DESC) explored data from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST)—and the first time Boston University hosted a DESC event.
DESC is an international science collaboration with over 1,450 members from over 27 countries. The group aims to make precise measurements using data from LSST with a goal of understanding the fundamental physics of the universe. Dillon Brout, a Hariri Institute Junior Faculty Fellow and an assistant professor of astronomy and physics, hosted the week-long event at BU, which included talks, breakout sessions, and open discussions, with the DESC Paris cohort joining over Zoom.
Brout has dedicated his career to probing the large-scale evolution of the universe. Recently, he received the 2026 New Horizons in Physics Prize for his work with cosmic microwave background (CMB) radiation left over from the Big Bang. He has also studied light from exploding stars (Type Ia supernovae), used as distance markers across the cosmos.
DESC connects Brout to other researchers on a mission to uncover the biggest mysteries of the universe—and the week-long event served as the beginning of a new era of this research.
The Rubin Observatory Opens New Possibilities
The universe is constantly expanding. Yet, it’s not at a constant rate; it’s speeding up. Since gravity is known to slow things down, there appears to be another anti-gravity force at work.
“We call whatever is causing that dark energy, but the remarkable thing is that we still do not know what dark energy actually is,” said Brout. “Understanding it is one of the biggest mysteries in physics. To figure that out, we need to observe an enormous amount of the Universe and catalogue it.”
In the past, gathering such a significant amount of data was a major obstacle for understanding the universe. That was until the Rubin Observatory initiated LSST—a 10-year time-lapse of the southern sky above Chile.
“A recent Rubin view of the COSMOS field contains more than half a million galaxies in a single patch of sky,” said Brout. “And Rubin will keep returning to those same fields again and again. We are not simply making a deeper picture of the Universe. We are beginning to make a movie of it.”
For years, DESC has prepared for LSST through simulations, software development, calibration, statistical methodology, and more. Now, with LSST underway and Rubin’s Data Preview 2 (DP2) becoming available, much of the conversation centered on aligning that preparatory work with the current data.
“With DP2, we are asking questions like: How accurate are the calibrations?” said Brout. “How uniform is the photometric and image quality? How well do our simulations reproduce the observations? What systematic effects remain? How should our analyses adapt to the current state of the images and our understanding of the instrument?”
Looking to the Future: Data Science and Cosmology Intersect
According to Brout, Rubin will generate tens of terabytes of data every night and ultimately produce roughly 20 petabytes of imaging data. The observatory is designed to process new observations and issue alerts within about 60 seconds. Millions of alerts then flow through a worldwide network of software brokers that classify and prioritize them, helping scientists determine which events require additional observations while they are still evolving.
“That combination of enormous data volume and real-time decision-making changes how survey cosmology has to operate,” said Brout. “We need distributed computing, sophisticated statistical inference, rapid classification and prioritization, and coordination between observatories and scientific teams around the world. It is a problem that naturally spans astronomy, physics, statistics, computing, and data science.”
That intersection of disciplines reflects the Hariri Institute’s commitment to convergent research—bringing together expertise from different fields to tackle complex problems—and is one reason Brout saw the Institute as a natural home for the DESC meeting.
“There is something particularly appropriate about the Hariri Institute being physically and intellectually situated at the intersection of astronomy, physics, computing, and data science at BU,” said Brout. “That is almost exactly where modern survey cosmology lives. Often someone working on a problem in statistics, computing, or data science is confronting a mathematical or computational problem remarkably similar to one we face in cosmology.”
For Brout, that need for collaboration extends beyond disciplines and institutions to the experiments themselves.
As DESC continues to pursue ongoing analysis of LSST data, he expects researchers will increasingly need to combine insights from different surveys to understand the physics shaping the universe.
“I do not think the next breakthroughs in dark energy will come from any single experiment,” said Brout. “Each experiment is observing a different piece of the same underlying physics. I think cross-survey cosmology will increasingly define the next decade of the field.”