Cambridge astronomers play leading role as world's most ambitious sky survey begins

Over the next ten years, the LSST will repeatedly photograph the entire southern sky to build an ultra-wide, ultra-high-definition time-lapse record of the Universe, helping to address some of astronomy's biggest open questions, including the nature of dark energy and the evolution of the Solar System, the Milky Way, and galaxies across cosmic time.

Cambridge's Institute of Astronomy and Kavli Institute for Cosmology have been central to UK preparations for over a decade, as part of the 36-institution LSST:UK Consortium, which has been backed by £23 million of investment from the Science and Technology Facilities Council (STFC). Now that the survey is underway, Cambridge researchers are playing leading roles in using its data — both in addressing foundational questions in cosmology and Galactic structure, and in building the tools that expand what the survey can detect.

Mapping the invisible architecture of the cosmos

Professor Hiranya Peiris, who holds the Professorship of Astrophysics (1909) at the Institute of Astronomy, is a Builder of the LSST Dark Energy Science Collaboration, one of the major international science teams that will use Rubin data to tackle foundational questions in cosmology.

"Now the decade-long movie of the Universe begins filming," said Peiris. "We've been building the tools to prepare for this data deluge for years. Rubin will image billions of galaxies, and my team is already using our generative models on the early data to extract their physical properties at scale. This is the survey that will let us map the invisible architecture of the cosmos."

Following in the tradition of SDSS

Professor Vasily Belokurov, also of the Institute of Astronomy, works on the structure and evolutionary history of the Milky Way.

"Wide-field sky surveys have transformed astronomy by turning the sky into a vast discovery space," said Belokurov. "The Sloan Digital Sky Survey was the true pioneer of this modern era, enabling breakthroughs that reached far beyond its original goals. The LSST will follow in that tradition, combining an unprecedentedly deep and wide view of the Universe with a programme specifically designed for discovery. Like SDSS before it, it will not only deliver on its scientific promise — it will surprise us."

Seeing further into the infrared

Cambridge expertise is also helping to extend the reach of the survey itself. Professor Richard McMahon, also of the Institute of Astronomy, is part of the team — led by Professor Manda Banerji at the University of Southampton, with Dr Elham Saremi and Dr Raphael Shirley of the Max Planck Institute for Extraterrestrial Physics — that has developed the LSST–VISTA Fusion Dataset. This combines Rubin's optical data with infrared observations from the Visible and Infrared Survey Telescope for Astronomy (VISTA), allowing astronomers to find distant, dust-obscured galaxies and black holes that would otherwise be missed by an optical survey alone. The resulting software will be made publicly available, enabling any astronomer to process data from their preferred telescope through the LSST data-processing pipeline.

A vast new dataset

Over its ten-year run, Rubin will catalogue an estimated 17 billion stars, 20 billion galaxies, and millions of changing objects in the sky — more than the number of people currently living on Earth. The survey is expected to generate up to 500 petabytes of data, of which the UK will process 25%, converting raw images into calibrated data products and operating a science platform used by 20% of the international LSST community.