NSF–DOE Vera C. Rubin Observatory Will Detect Millions of Exploding Stars

Measuring distances across the Universe is much more challenging than measuring distances on Earth. Is a brighter star closer to Earth than another, or is it just emitting more light? To make confident distance measurements, scientists rely on objects that emit a known amount of light, like Type Ia supernovae.

These spectacular explosions, among the brightest to ever be recorded in the night sky, result from the violent deaths of white dwarf stars and provide scientists with a reliable cosmic yardstick. Their brightness and color, combined with information about their host galaxies, allow scientists to calculate their distance and how much the Universe expanded while their light made its journey to us. With enough Type Ia supernovae observations, scientists can measure the Universe’s expansion rate and whether it changes over time.

Although we’ve caught thousands of Type Ia supernovae to date, seeing them once or twice is not enough — there is a goldmine of information in how their fleeting light varies over time. NSF–DOE Vera C. Rubin Observatory will soon begin scanning the southern hemisphere sky every night for ten years, covering the entire hemisphere approximately every few nights. Every time Rubin detects an object changing brightness or position it will send an alert to the science community. With such rapid detection Rubin will be our most powerful tool yet for spotting Type Ia supernovae before they fade away.

Rubin Observatory is jointly funded by the U.S. National Science Foundation and the U.S. Department of Energy’s Office of Science. Rubin is a joint Program of NSF NOIRLab and DOE’s SLAC National Accelerator Laboratory, who will cooperatively operate Rubin.

Scientists like Anais Möller, a member of the Rubin/LSST Dark Energy Science Collaboration, look forward to Rubin’s decade-long Legacy Survey of Space and Time (LSST), during which it’s expected to detect millions of Type Ia supernovae. “The large volume of data from Rubin will give us a sample of all kinds of Type Ia supernovae at a range of distances and in many different types of galaxies,” says Möller.

In fact, Rubin will discover many more Type Ia supernovae in the first few months of the LSST than were used in the initial discovery of dark energy — the mysterious force causing the Universe to expand faster than expected based on gravitational theory. Current measurements hint that dark energy might change over time, which if confirmed could help refine our understanding of the Universe’s age and evolution. That in turn would impact what we understand about how the Universe formed, including how quickly stars and galaxies formed in the early Universe.

With a much larger set of Type Ia supernovae from across the Universe scientists will be able to refine our existing map of space and time, getting a fuller picture of dark energy’s influence. “The Universe expanding is like a rubber band being stretched. If dark energy is not constant, that would be like stretching the rubber band by different amounts at different points,” says Möller. “I think in the next decade we will be able to constrain whether dark energy is constant or evolving with cosmic time. Rubin will allow us to do that with Type Ia supernovae.”

Every night Rubin Observatory will produce about 20 terabytes of data and generate up to 10 million alerts — no other telescope in history has produced a firehose of data quite like this. It has required scientists to rethink the way they manage rapid alerts and to develop methods and systems to handle the large incoming datasets.

Rubin’s deluge of nightly alerts will be managed and made available to scientists through seven community software systems that will ingest and process these alerts before serving them up to scientists around the world. Möller, together with a large collaboration of scientists across expertises, is developing one of these systems, called Fink.

The software systems collect the alerts from Rubin each night, merge Rubin data with other datasets, and, using machine-learning, classify them according to their type, such as kilonovae, variable stars, or Type Ia supernovae, among others. Scientists using one of Rubin’s community systems, like Fink, will be able to sort the massive dataset of alerts according to selected filters, allowing them to quickly home in on the data that are useful for their research.

“Because of the large volumes of data, we can’t do science the same way we did before,” says Möller. “Rubin is a generational shift. And our responsibility is developing the methods that will be used by the next generation.” 

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, is a groundbreaking new astronomy and astrophysics observatory under construction on Cerro Pachón in Chile, with first light expected in 2025. It is named after astronomer Vera Rubin, who provided the first convincing evidence for the existence of dark matter. Using the largest camera ever built, Rubin will repeatedly scan the sky for 10 years and create an ultra-wide, ultra-high-definition, time-lapse record of our Universe.

NSF–DOE Vera C. Rubin Observatory is a joint initiative of the U.S. National Science Foundation (NSF) and the U.S. Department of Energy’s Office of Science (DOE/SC). Its primary mission is to carry out the Legacy Survey of Space and Time, providing an unprecedented data set for scientific research supported by both agencies. Rubin is operated jointly by NSF NOIRLab and SLAC National Accelerator Laboratory. NSF NOIRLab is managed by the Association of Universities for Research in Astronomy (AURA) and SLAC is operated by Stanford University for the DOE. France provides key support to the construction and operations of Rubin Observatory through contributions from CNRS/IN2P3. Rubin Observatory is privileged to conduct research in Chile and gratefully acknowledges additional contributions from more than 40 international organizations and teams.

The U.S. National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.

The DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. 

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag (Kitt Peak) to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.

SLAC National Accelerator Laboratory explores how the universe works at the biggest, smallest and fastest scales and invents powerful tools used by researchers around the globe. As world leaders in ultrafast science and bold explorers of the physics of the universe, we forge new ground in understanding our origins and building a healthier and more sustainable future. Our discovery and innovation help develop new materials and chemical processes and open unprecedented views of the cosmos and life’s most delicate machinery. Building on more than 60 years of visionary research, we help shape the future by advancing areas such as quantum technology, scientific computing and the development of next-generation accelerators. SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science.

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