When a Picture Is Worth a Billion Worlds: Duke Cosmologists Celebrate the Rubin Observatory’s First Images

Duke’s football stadium scoreboard is accustomed to displaying impressive images. On June 23rd, however, it had the privilege of displaying images unlike any other before: the cosmos, as seen in the first photographs released by the NSF–DOE Vera C. Rubin Observatory. 

From the identification of its ideal site on a Chilean mountaintop 8,684 feet above sea level to the fine-tuning of its software, thousands of researchers have played a role in ensuring that the Rubin Observatory’s extraordinarily ambitious goal — to uncover the secrets hidden in the night sky — is fulfilled. Their work will revolutionize our understanding of the universe —and may even change physics itself.

Huddled in the shade among those who braved the heat to attend Duke’s First Watch Party were four Duke cosmologists who had a hand in bringing the cosmos to the hundreds of watch parties being hosted across the world, including at Wallace Wade Stadium.

Professor of Physics Christopher Walter is the one to blame — or rather, praise — for Duke’s strength in cosmology. As the founding member of Duke’s Cosmology group, he joined the international collaboration that became the Rubin Observatory in pursuit of his interest in dark energy, and out of a desire to work collaboratively with others. Over the next 12 years, four cosmologists joined him in the Duke Physics Department, each with their own group of students and postdocs, turning Duke Cosmology into an international powerhouse.

“We really strive to be the best place in the country to work on survey cosmology,” Walter says. “We work in teams, and nobody does just their own thing. People are involved in commissioning instruments, they’re working on the infrastructure of the codes that we use, they’re working in leadership. So, for those of us working on Rubin, we've all spent a lot of time trying to get the telescope running.”

But what will the telescope do, exactly? Over the course of 10 years, the Rubin Observatory will repeatedly photograph each section of the cosmos every three days, for a survey called the Legacy Survey of Space and Time (LSST). Combined in a time-lapse movie, these images will reveal with unparalleled precision and depth not only what the sky looks like on any given night, but also which celestial objects have changed in brightness, position or behavior over days, months, or years.

Bekah Polen is a Ph.D. student in the Duke Cosmology group whose interest in understanding dark energy led to a desire to obtain the most precise images possible of the universe. She exemplifies the collaborative approach Walter describes.

"I came to Duke with the goal of studying weak gravitational lensing, which is one of the probes we use to study dark energy by mapping where matter is in the universe and how it's evolved over time," she says. "The quality of weak lensing data we’ll get from Rubin depends on how focused and high quality the images are, and I work on a team that helps the telescope operate its control system to keep it as focused and sharp as possible.”

To take such high-quality images, the Vera Rubin Observatory houses the biggest digital camera ever built. Weighing as much as a pickup truck, it boasts an unprecedented 3,200-megapixel resolution. HyeYun Park, a postdoctoral researcher working with Walter, is a commissioning scientist on the ground at the Observatory, ensuring the telescope and dome work as they should.

“I chose to study astrophysics in grad school because I was fascinated by how the universe is made, but I’ve always been more interested in things I can physically touch and play with, so for my Ph.D. I focused on camera sensors, and how sensor effects influence weak lensing studies," she shares. 

"As I moved on to postdoc positions, I came to Chile and expanded from sensors to the whole Rubin Observatory instrumentation."

Upon arriving in Chile in 2022, she met with Walter, who spent two years on site. "We were helping build the telescope, testing it, and analyzing how it works and how to improve it — like making the image quality better or making the telescope move more safely."

Taking one such ultra-precise image every 40 seconds, the Rubin Observatory will produce hundreds of massive files. Processing them and turning them into usable data will require lots of new software. That’s where Assistant Research Professor of Physics Arun Kannawadi thrives.

“I'm kind of like the opposite of HyeYun, I don't do well with hardware. I feel like I might actually break things,” he laughs. “I'm much more comfortable with software, writing code. So that's my niche in the Rubin.”

As it surveys the night sky, the Rubin Observatory will photograph the same point multiple times per night. “My job is making sure that we can stack all of these photographs to make a much deeper image, so we begin to see fainter and fainter galaxies and can reliably measure their properties — how bright they are, what kind of shape they have,” Kannawadi says. “That feeds into the way we extract the weak gravitational lensing signal.” 

The sheer amount of data is a challenge. In one night, the Rubin Observatory will produce approximately 20 terabytes of raw data every night — more data than you’d need to stream 50 years of music non-stop. In 10 years, Rubin data processing will generate around 500 petabytes — roughly the same amount of content written in every language throughout human history.

“That's where a lot of my work comes in,” says Kannawadi. “The petabytes of data are a challenge by themselves, so a lot of my research just asks ‘what is the best way to compute these quantities? What is the best way of storing this amount of data?”

“Those are all efforts to actually put the telescope together and make it work,” summarizes Walter. “But also, the way that you can do good science is by really understanding the instruments that you work on.”

And if helping map the entire universe, understanding dark energy and possibly rewriting the laws of physics weren’t enough, the innovations developed for the Rubin Observatory by Kannawadi, Walter, Park, Polen and the thousands of researchers involved in its development can bring future applications in fields as wide as data management, wireless connections, camera optics and robotics. Oh, and they can also help detect killer asteroids — an adventure that Maryann Benny Fernandes, another Ph.D. student in the group, is interested in.

To our Duke Cosmologists, the striking images on the Duke scoreboard symbolize a door into their wildest research dreams. 

“With better data, we will be able to actually test hypotheses and answer really existential questions,” says Kannawadi. “That excites me.”

 “I’m really excited to do this ‘hands-on’ cosmology,” says Walter. “I want to be involved in understanding the truly fundamental nature of how things work. And I hope what it means is that we'll learn something completely new about the universe and the way space-time works.”

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NSF–DOE Vera C. Rubin Observatory, funded by the U.S. National Science Foundation and the U.S. Department of Energy’s Office of Science, will perform the Legacy Survey of Space and Time using the LSST Camera and the Simonyi Survey Telescope. Rubin Observatory is a joint Program of NSF NOIRLab and DOE’s SLAC National Accelerator Laboratory. To learn more about it, visit their website.