Secrets of the stars

How UW astronomers, the world’s largest survey telescope and a revolutionary new view of space will upend what we thought we knew about the universe.

Beneath breathtakingly crisp views of the night sky, atop Cerro Pachón, a mountain in the foothills of the Andes in northern Chile, is a nearly finished construction project that will transform how we look at the universe. Though it resembles a postmodern office building, its domed tower is the telltale sign of an astronomical observatory.

Next year, when its upward-turned eye opens to the heavens, the Vera C. Rubin Observatory will form the beating heart of a revolution that is sweeping astronomy. It will impact nearly every mission, every question and every research project exploring what is “out there” beyond Earth. It could even change how we view our place within the cosmos.

Assuming, of course, astronomers can navigate their way through the unprecedented amount of data the Rubin Observatory will gather starting in 2025 — a challenge that the UW is rising to meet.

The Rubin Observatory, which features a 27-foot mirror and the largest digital camera ever constructed, will unleash a deluge of information about our night sky as part of the 10-year Legacy Survey of Space and Time (LSST). The University of Washington was a founding member of the LSST mission, which is no ordinary stargazing venture.

Thanks to the observatory’s Simonyi Survey Telescope, the LSST will be the most ambitious mission ever to capture and understand the countless cosmic events that shape and reshape our universe — effectively rewriting the astronomy books we use today.

“A generation ago, a telescope might watch just a thousand stars in a single observation run,” says James Davenport, assistant professor of astronomy in the College of Arts & Sciences. “The Rubin Observatory will observe several billion objects in the sky, giving us thousands of times more data than other telescopes could capture — and that’s just in a single night.”

But data on its own can’t drive discovery. The astronomers need tools — algorithms, software and expertise — to sort through Rubin’s bounty.

“It’s like someone delivering a silo of grain and saying, ‘Here, I’ve solved your hunger problem.’ You actually haven’t yet — not until we have the means to process that grain and bake loaves,” says Mario Jurić, a UW astronomy professor. “We’ll get silos of grain each night from the Rubin Observatory, and the field of astronomy needs to figure out how to transform that into bread.”

This is where DiRAC — the UW’s Institute for Data Intensive Research in Astrophysics & Cosmology — comes in. Launched in 2017 with lead funding from the Charles and Lisa Simonyi Fund for Arts and Sciences, DiRAC is ready to help us make sense of the discoveries of Rubin and the new generation of telescopes.

Feeding astronomy’s hunger

Jurić and Davenport are the director and associate director (respectively) of DiRAC, a collaborative community of scientists, engineers and students who are crafting software that can comb through those mountains of astronomical data to help scientists understand the events and changes unfolding continuously above our heads.

Each night, the Rubin’s camera is expected to capture millions of changes in stars and other objects — too many to sort through in a lifetime.

The astronomical events the LSST will pick up are diverse. Some will be subtle, like a dim asteroid in a frigid orbit around the sun. Others will be dramatic, like a massive star at the end of its life immolating brilliantly as a supernova.

The tools DiRAC is developing for the Rubin project are equally diverse. Daily automated alerts, for example, will help scientists worldwide identify events that require immediate action — such as an asteroid on a collision course with Earth. Other tools will enable longer-term studies, like tracking the behavior of a specific set of stars over time in our Milky Way galaxy.

“These are important tools to help democratize science and make it accessible,” says Jurić. “Most astronomers are not experts in writing algorithms or software to sort through large datasets. The tools we’re developing will do those jobs for them, so users can pull out the data that interests them and keep the discovery pipeline going.”

Beyond these tool-building goals, DiRAC scientists are looking forward to applying LSST data to a host of scientific mysteries.

The Rubin Observatory will impact nearly every mission, every question and every research project exploring what is “out there” beyond Earth. It could even change how we view our place within the cosmos.

Data on its own can’t drive discovery. Astronomers need tools — algorithms, software and expertise — to sort through Rubin’s bounty. “It’s like someone delivering a silo of grain and saying, ‘Here, I’ve solved your hunger problem.’ You actually haven’t yet — not until we have the means to process that grain and bake loaves,” says Mario Jurić, UW astronomy professor and director of DiRAC. “We’ll get silos of grain each night from the Rubin Observatory, and the field of astronomy needs to figure out how to transform that into bread.”

Photo by Christopher Michel

Finding the strange and powerful

Many of us remember making solar-system mobiles in school, with eight (or nine, depending on our age) painted balls representing the planets — but it turns out the solar system is far more crowded than we were taught.

After “first light” — when Rubin becomes operational in early 2025 — DiRAC scientists will use the data to understand our astronomical history, observe the present and predict the future, tracking and studying everything from protecting ourselves from near-Earth asteroids to the possibility of finding a Planet Nine lurking in the frozen reaches beyond our star.

DiRAC researcher Sarah Greenstreet works alongside teams that are creating an automated alert system for objects in motion that could impact the Earth. She notes that asteroids and other small bodies around the sun are also windows to the past — “which can help us understand how they have moved through the solar system throughout its history.”

Other DiRAC scientists will have their gazes fixed on stars themselves. Contemporary research is challenging long-prevailing theories about how these burning furnaces form, live and die. In his own research, Davenport — who notes that he “likes weird stars” — has catalogued unexpected stellar pairings, such as a large puffy star (one that’s expanding in its twilight years) orbited by a small companion star encased in cosmic dust, or two stars whose dance around each other is twisted and turned by an unseen third companion. With the LSST watching hundreds of millions of stars each night, scientists like Davenport expect to find more of these strange systems and learn why some stars are paired up while others, like our calm sun, are not.

“A bunch of stars out there show unusual and unexpected behavior,” says Davenport. “Is it possible that they aren’t unusual at all, but are actually very common? If so, we’ll have to go back to the theories of star formation and galaxy formation and redefine what’s ‘unusual.’”

Still other DiRAC researchers have their eyes on even bigger prizes, including the powerful events — like black hole or neutron star mergers — that generate gravitational waves. The LSST mission will provide data about the highly energetic events that generate these waves, giving scientists valuable insight never before available.

DiRAC researcher Sarah Greenstreet is working on an automated alert system for objects in motion that could impact the Earth. She notes that asteroids are also windows to the past — “which can help us understand how they have moved through the solar system throughout its history.”

Looking for the unexpected

Those are just a few of the discoveries scientists expect to find. But buried within the massive datasets from LSST and the Rubin Observatory will doubtless be evidence of events, objects and phenomena that may shock and confound scientists.

Those “anticipated unknowns,” pulled from the sky above the arid Andes and then examined at a rain-washed campus half a world away, are what most excite astronomers like Davenport. “The lasting legacy of the LSST will be in the surprises buried in the datasets that we’re helping to uncover,” he says with anticipation. “Students today will be working with these data for the rest of their careers — and that is precisely how astronomy should work.”