The biggest sky survey ever attempted has begun, and Denmark is in

After more than two decades from first sketch to first survey night, the Vera C. Rubin Observatory has begun its main mission: scanning more than half of the entire sky every few nights, for ten years, with the largest digital camera ever built. The result will be an unprecedented time-lapse movie of the Universe that lets astronomers watch the cosmos change in close to real time, including asteroids drifting past Earth, stars exploding in distant galaxies, and the faint, hidden fingerprints of dark matter and dark energy.

The numbers are staggering. Every night the observatory gathers around 20 terabytes of data and can fire off millions of automated alerts the instant something in the sky moves, brightens, fades or appears for the first time. Over the decade, LSST is expected to map roughly 20 billion galaxies, measure some 17 billion stars in the Milky Way, and catalogue around 6 million bodies in the Solar System and millions of new supernovae and transients in distant galaxies. The system is already working. From its first nights, Rubin’s alerts have streamed to data brokers around the world, flagging new exploding stars for astronomers to chase within hours of detection.

Denmark is one of the international partners taking part. Through the Instrument Center for Danish Astrophysics (IDA), Danish institutions have established a national Independent Data Access Center (the Danish IDAC, or DK-IDAC) as an in-kind contribution to the Rubin Observatory. In return, researchers at Danish institutions can get formal data rights, meaning direct access to the proprietary LSST data stream and to the international science community built around it.

“For fourteen years we’ve been knocking on this door, and now it has opened. Every night, Rubin pours a firehose of data into Denmark: millions of things that move, flare or explode across the sky, now open for our researchers to explore. There are discoveries in there that no one has dreamed of yet, and overnight the sky has become a laboratory for Danish scientists,” says Christa Gall, Associate Professor at DARK / Niels Bohr Institute, University of Copenhagen, who has led the Danish effort to join LSST.

"Observations with Rubin will be used to put the standard model of cosmology to a stringent test. Rubin may transform our understanding of dark matter and dark energy, two mysteries of modern cosmology and key elements of the standard cosmological model." says  Radoslaw Wojtak, Associate Professor at DARK / Niels Bohr Institute, University of Copenhagen, who led the Danish IDAC proposal.

A 14-year effort

Denmark’s involvement has been a long time in the making. The first Danish notice of intention to contribute to LSST was submitted in 2011, followed by national workshops in 2013, 2015 and 2022 and, eventually, a formal agreement with the Rubin Observatory. Joining LSST has been a national priority for IDA.

Funded through Villum Foundation research grants, IDA and the University of Copenhagen’s Faculty of Science high-performance computing, the Danish data centre lets researchers work with the LSST data directly, on Danish infrastructure and with substantial computing power and storage, rather than depending entirely on facilities abroad. Danish researchers are interested in the full range of LSST science, including dark energy, the structure of the Milky Way, exploding stars, and the changing, “transient” Universe.

Much of this depends on artificial intelligence. LSST’s nightly data tsunami, with millions of alerts and billions of objects, cannot be sorted by hand. The Danish IDAC is being built as a platform for hosting and co-developing data-processing and machine-learning pipelines. These include those that produce joint ground based Rubin LSST and ESA's Euclid space mission’s data products or estimate photometric redshifts, the distances to galaxies. Combining LSST-scale data with the IDAC’s hardware also invites a wider range of future AI and machine-learning work, both within astrophysics and at the interface with adjacent data-intensive fields, developed together with partners such as the NSF SkAI Institute (Chicago, US) and the LSST Dark Energy Science Collaboration.

This Rubin and Euclid combination is itself unusual as it is a pairing very few groups anywhere can make, since LSST is largely a U.S.-led project and Euclid an almost exclusively European one. But that is only one project. The data centre is meant to support many more, across the wide range of science that LSST will make possible.

“For me, combining Rubin and Euclid data with the most cutting edge AI methods we’re developing at SkAI is the key to understanding dark energy and dark matter, and understanding the transient sky, and it is a privilege to work with Christa and her team at DARK / NBI. We could not do this without her and her team.” said Prof. Gautham Narayan, the Deputy Director of SkAI, and spokesperson for the Dark Energy Science Collaboration.

“Rubin and Euclid together give us something no single facility can: the same sky seen from the ground and from space, in visible and infrared light at once. Few groups anywhere hold both, and that combination is exactly where the discoveries of the next decade will be made,” says Jens Hjorth, Professor at DARK / Niels Bohr Institute, University of Copenhagen.

About the observatory

The Vera C. Rubin Observatory sits on the Cerro Pachón ridge in the Atacama, in northern Chile. Its 8.4-metre Simonyi Survey Telescope uses an unusual three-mirror design and feeds a 3,200-megapixel camera, the largest digital camera ever built for astronomy, whose front lens holds a Guinness World Record as the largest ever made. The survey works on a “Wide-Fast-Deep” principle: imaging large patches of sky, quickly, down to very faint objects, in six optical filters, and revisiting each point on the sky on average around 825 times over ten years.

The observatory is jointly funded by the U.S. National Science Foundation (NSF) and the U.S. Department of Energy’s Office of Science (DOE), and operated jointly by NSF NOIRLab and DOE’s SLAC National Accelerator Laboratory. It is named for the American astronomer Vera C. Rubin, whose work provided key early evidence for dark matter, and it is the first major publicly funded U.S. astronomical facility named after a woman.

LSST is designed to advance four science areas: understanding the nature of dark matter and dark energy; taking an inventory of the Solar System; mapping the structure of the Milky Way; and exploring the transient and variable Universe.

Media contact

For inquiries about the Danish contribution and the DK-IDAC, contact Christa Gall, email: christa.gall@nbi.ku.dk/ phone: +45 53662018 or institutional press office.

About the Instrument Center for Danish Astrophysics (IDA)

The Instrument Center for Danish Astrophysics (phys.au.dk/ida) is a national center funded by the Danish Agency for Science and Higher Education. It brings together Danish institutions contributing to research and teaching in astrophysics, with a structure designed to ensure strategic coordination of academic activities in Danish astrophysics. IDA consists of a Board, an Executive Committee and 13 working groups that strengthen collaboration between the Danish academic environments working in astronomy and astrophysics.

Useful links

• Rubin Observatory: https://rubinobservatory.org/
• LSST: https://www.lsst.org/
• Data Preview overview: https://dp1.lsst.io/overview/index.html
• Rubin images are free for press use with credit. Image source https://rubinobservatory.org/gallery/collections/first-look-gallery/mlis3sriah6pn6nfr5ecp46h3i

• Vera C. Rubin Observatory website
• Vera C. Rubin Observatory image gallery
• More Rubin images
• More Rubin videos
• Check out other NOIRLab Organization Releases
• Press release on rubinobservatory.org
• Press release from SLAC

Links to LSST press release: https://rubinobservatory.org/news/action-rubin-lsst-begins