In this thesis we push the boundaries of high-resolution imaging at radio frequencies between 100 and 200 MHz. Using the International LOFAR Telescope that spans across Europe we achieve sub-arcsecond angular resolution.

This thesis develops a method for direction dependent calibration of the ionosphere in radio interferometric data.

Following the Big Bang, structure in the Universe started collapsing under the force of gravity. This resulted in the formation of the first stars, galaxies and clusters of galaxies.

Many galaxy clusters exhibit bright diffuse radio emission that traces the underlying structure of the intracluster medium (ICM).

This thesis utilises the exceptional sensitivity and resolution of LOFAR to explore the low-frequency Universe, while simultaneously advancing the telescope's capabilities to enable new scientific discovery.

On the largest scale, the Universe resembles a cosmic spiderweb. Most galaxies coexist in small groups within the threads of this web. At the nodes of the threads are enormous groups of galaxies forming the largest structures in the universe still held together by gravity: clusters of galaxies.

The radio sky harbours both galactic and extragalactic sources of arcminute- to degree-scale emission of various physical origins. To discover extragalactic diffuse emission in the Cosmic Web beyond galaxy clusters, one must image low–surface brightness structures amidst a sea of brighter compact fore-…

In this thesis, I study the formation of large-scale structure and the physics of particle acceleration at large scales (~Mpc).

In this thesis, we use low-frequency and high-frequency radio observations to address the following questions regarding quasars: is the radio loud/quiet quasar dichotomy real?

The Education Office Astronomy supports all aspects of the Astronomy bachelor and master education programmes. Its main focus is on education quality assurance, student monitoring, education-related PR, student recruitment, job market orientation and alumni policy.

The mission of Software and AI in Business (SA&B)connects the domains of science, business, and policy. Scientific research we focus on at Leiden in areas such as artificial intelligence promises to reshape our societies for the better. Translating science into positive societal impact however requires…

On this page you will find an overview of awards and prizes granted to our staff and students in 2026, as well as special appointments at Leiden University and other institutions.

A galaxy is already incredibly large, but it can get even bigger. Astronomer Reinout van Weeren investigates clusters of galaxies, one of the largest structures in the universe. For his research into the origins and evolution of these clusters, he obtained an ERC Starting Grant of 1.5 million euros.…

Jordy Bouwman and future Sterrewachter Reinout van Weeren have been awarded a Vidi subsidy to set up or expand their own line of research.

Starting 1 September, three new Programme Directors will begin at FWN. Daan van der Es, Reinout van Weeren, and Amineh Ghorbani will each be responsible for a master's programme in our faculty.

Not everything that comes close to a black hole is swallowed by it. Black holes can also hurl material away, and that chance turns out to be considerably bigger than previously thought. Martijn Oei's accidental discovery and his subsequent research on it earned him a cum laude promotion on 12 Decemb…

An international team of researchers led by astronomers from Leiden University (the Netherlands) has produced the first sharp radio maps of the universe at low frequencies. Thanks to a new calibration technique, they bypassed the disturbances of the Earth's ionosphere. They used the new method to study…

The European Research Council has awarded a Starting Grant to five early career scientists from Leiden University. They received funding up to 1.5 million euros to further expand on their research subject.

An international team of astronomers led by Dutch scientist Martijn Oei has discovered the largest pair of jets from a black hole ever seen. The 'jumbojets' extend a combined length of 140 Milky Ways. The Leiden Observatory played a prominent role in this research. The publication will feature on the…

An international team of scientists including Leiden's Joe Callingham has discovered nineteen red dwarf stars that unexpectedly emit radio waves. The outbursts possibly originate from interaction with exoplanets. The results of the research appear in two scientific publications.

The shock wave triggered by one of the five galaxies making up the iconic Stephan’s Quintet appears to be less disruptive than previously thought, with the shock likely being cushioned by dust particles in the surrounding gas. This is according to the analysis of the first scientific observations of…

An international team of astronomers has published a map of the sky showing over 25,000 supermassive black holes. The map, to be published in the journal Astronomy & Astrophysics, is the most detailed celestial map in the field of so-called low radio frequencies. The astronomers, including Leiden astronomers,…

Three Leiden researchers have been awarded a Vici grant by the Dutch Research Council. The funding of up to 1.5 million euros supports ‘talented, adventurous and pioneering researchers’. A total of 39 projects at Dutch institutions will receive a grant.

An overview of awards and prizes granted to our staff and students in 2017, as well as special appointments and royal distinctions.

How unique is the human capacity for learning and adapting to an environment? In field research – in the rainforest and Artis Zoo – primatologist Karline Janmaat is studying how humans and other primates adapt to their environment in their search for food. She will give her inaugural lecture as Professor…

By a stroke of luck, a team led by Dutch PhD student Martijn Oei has discovered a radio galaxy of at least 16 million lightyears long. The pair of plasma plumes is the largest structure made by a galaxy known thus far. The finding disproves some long-kept hypotheses about the growth of radio galaxie…

An international team of researchers observed the full extent of the evolution of hot gas produced by an active black hole for the first time. As it evolves, the hot gas encompasses a much larger area than previously thought and even impacts objects residing at great distances. Their study is published…

Galaxies are often found in clusters, which contain many “red and dead” members that stopped forming stars in the distant past. Now, an international team of astronomers, led by Andra Stroe of Leiden Observatory and David Sobral of Leiden and the University of Lisbon, has discovered that these comatose…

The radio telescope LOFAR, with a major contribution from Leiden Observatory, has produced the most detailed radio map of the Universe ever made. Never before have so many cosmic radio sources been captured in a single survey: 13.7 million.

An international team of more than 200 astronomers from 18 countries has published hundreds of thousands of unknown galaxies. The data are part of a project lead by Leiden professor of Observational cosmology Huub Röttgering. Both Dutch and international media reported extensively about the publica…

Through the clever use of two types of telescopes, a team of researchers has produced stunning images of clusters of galaxies. This not only produces beautiful images, but also provides more information about the enormous amounts of energy released around supermassive black holes in clusters. The astronomers,…

An overview of awards and prizes granted to our staff and students in 2018, as well as special appointments and royal distinctions.

A Dutch-Italian-German team of astronomers has observed a huge glow of radio emission around a cluster of thousands of galaxies. They combined data from thousands of LOFAR antennas that were focused for 18 nights on an area the size of four full moons. This is the first time astronomers have been able…

An international team of researchers led by Leiden University (the Netherlands) has mapped nine gigantic collisions of galaxy clusters. The collisions took place seven billion years ago and could be observed because they accelerate particles to high speeds. It is the first time that collisions of such…

On this page you will find an overview of awards and prizes granted to our staff and students in 2024, as well as special appointments at Leiden University and other institutions.

Eleven talented Leiden researchers with several years of research experience have been awarded a Vidi subsidy to set up or expand their own line of research.

With new algorithms and supercomputers, an incredibly detailed radio map of the universe was created. Now astronomers can look at radio data of galaxies with much more precision. This was published in Nature Astronomy by Leiden PhD student Frits Sweijen and colleagues.

They first entered the Academy Building fifty to sixty years ago. On 28 March, they were back for an afternoon: the members of the Dr Pfiffikus debating society of the German Studies programme. Former chair Hans van der Veen looks back on his student days.

PhD defence

PhD defence

Many of our staff and students have won prizes over the past year. Others have been awarded a subsidy, or, because of their eminence in their field, they have been appointed members of academic societies or have taken up positions in the community. Reasons enough to be proud of them and to include them…

Over the past year, many of our staff and students have won prizes, been awarded a substantial grant or been appointed to an academic association or a position in public life. All of these are good reasons to include them in our 2018 Hall of Fame. We are proud of them all.