Image: Sensor of the Large Synoptic Survey Telescope before installation. Photographer: Stephen Thorp.

Researchers from both the Department of Physics and the Department of Astronomy at Stockholm University submitted the successful funding application. The team has since been further strengthened by the recruitment of Ragnhild Lunnan, whose research is supported by a grant from the European Research Council (ERC). Altogether, the group now comprises over 16 people, including six senior researchers and ten doctoral students and students.

Scientific initiatives cover several key areas

Ariel Goobar, alongside Jesper Sollerman and Ragnhild Lunnan, leads research on transients, primarily supernova explosions. Jens Jasche focuses on the large-scale structure and evolution of the universe, while Hiranya Peiris and Mathew Hayes investigate galaxy properties and their evolution over cosmic time.

These approaches are used to study the composition of the universe, including properties of dark matter and dark energy. The new information is expected to yield deeper insights into astrophysics, including galaxy evolution and stellar explosions.

Space researchers worldwide have long utilized the Zwicky Transient Facility (ZTF), which images the entire northern celestial hemisphere every three nights, identifying short-lived events like supernovae. Every night, nearly one million alerts are sent out to scientists who then activate other telescopes for detailed studies.

Read more about ZTF and how researchers at the Oskar Klein Centre use the observatory to discover supernovae.

"LSST represents a huge leap forward compared to the current Zwicky Transient Facility," says Ariel Goobar. "The principle remains the same: repeatedly observing the same sky region to spot changes, but LSST offers much higher resolution and greater depth. However, the observations are less frequent, making short-duration events easier to miss."

Spiral galaxies, interacting galaxies, and more can be seen in this small portion of a larger image of the Virgo Cluster taken by the Vera C. Rubin Observatory. Photographer: NSF–DOE Vera C. Rubin Observatory.

Explore more images from the telescope on Vera C. Rubin's website!

A crucial difference between LSST and ZTF is that LSST captures darker skies, enabling observation of distant objects, while ZTF targets brighter, closer phenomena. Additionally, the difference in their mirror sizes is significant, with LSST’s primary mirror measuring 8.4 meters compared to ZTF’s 1.2 meters.

After 2026, OKC will end its collaboration with ZTF, but starting in August this year, a related project with LS4 — a smaller telescope in the southern hemisphere scanning the same sky area as LSST — will commence.

The OKC engagement in LSST is also a part of the new EDUCATE centre. An excellence centre funded by the Swedish Research Council focusing on unraveling the enigmas posed by the dark universe using novel facilities and analysis methods.

The initiative also includes laboratory research into dark matter. Researcher Jun-Woo Jeoung from OKC is involved in the international ALPHA project, investigating axions, hypothetical particles that could solve the mystery of dark matter. Experiments at the Gran Sasso laboratory in Italy, involving OKC researchers like Jan Conrad, might also become central to studying other dark matter candidates.

"Regarding dark energy, we hope LSST will clarify whether its properties have changed over cosmic time or remained constant," says Ariel Goobar.

LSST generates enormous data volumes 

Stephen Thorp (OKC), postdoctoral researcher and member of the LSST Dark Energy Science Collaboration, works with advanced broadband filtering and machine learning techniques to determine galaxy redshifts. The need is considerable, as manually obtaining spectra of the billions of observed galaxies is impractical.

Thorp looks forward to using the data to develop sophisticated galaxy models:
 "The vast data volume and depth of LSST will not only provide tighter cosmological constraints but also reveal new aspects of galaxy diversity and evolution. It's an incredibly exciting time for astronomical research," he says.

Due to LSST observing such a vast sky area with unique depth, the project expects to detect many gravitationally lensed supernovae. Light from these supernovae passes close to foreground galaxies, becoming magnified as if passing through a giant optical lens.

Image: Rendering of LSST (Large Synoptic Survey Telescope) by LSST Project Office.

"With LSST, we expect to detect roughly one lensed supernova per week — a dramatic improvement compared to previous efforts where finding just one event required several years," says Ariel Goobar.

OKC researchers are also developing methods to swiftly identify these supernovae among millions of nightly observations. Cameron Lemon at the Centre is compiling a catalog of known gravitational lenses to facilitate future identification of lensed supernovae.

"Identifying image positions at a fraction of a pixel level is crucial for spotting lensed supernovae. When we take multiple images of a supernova, these images may differ slightly over time and angular shifts, appearing as small movements due to gravitational lenses," Ariel Goobar concludes.

Postdoctoral researchers Aline Chu and Priscila J. Pessi at OKC also emphasize LSST’s potential. Chu develops machine learning algorithms to study Brightest Cluster Galaxies (BCGs)—the universe's most massive galaxies—while Pessi uses LSST simulations to predict how extremely luminous supernovae will appear.

"LSST will revolutionize transient astronomy and enable systematic studies of the most distant and faint objects previously challenging to investigate," says Pessi.