Hot astrophysical plasma is ubiquitous in the Universe, from comets in our Solar system to the largest scale structures -- the cosmic web filaments. These hot plasmas, with the temperature of a few millions of degrees, are often observed in the X-ray wavelength range.

Dark matter is one of the biggest mysteries of the Universe. Its properties cannot be explained with the known laws of physics and elementary particles.

When galaxies collide, do the black holes at their centre form a supersized black hole? This is what we think happens, but it's not as simple as that, according to Simon Portegies Zwart. Zwart, computer scientist and astronomer, has been awarded a VICI grant to research this phenomenon.

Galaxies in the Universe are distributed along the intricate framework of the Cosmic Web. Groups and clusters of galaxies comprise the densest regions in this network, and therefore, are excellent cosmic laboratories to study different aspects of galaxy evolution in extreme environments.

In 2015, Jorryt Matthee thought he discovered an extremely distant galaxy called CR7, which lacked elements heavier than helium. Three years later, he shows with measurements using the ALMA telescope that the galaxy does have carbon after all, and even in normal concentrations. The American Astronomical…

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.…

A team of Leiden astronomers used the latest set of data from ESA’s Gaia mission to look for high-velocity stars being kicked out of the Milky Way, but were surprised to find stars instead sprinting inwards – perhaps from another galaxy.

The book 'Darwin comes to town’ by Menno Schilthuizen has been awarded the best nature book in the Netherlands. The Leiden biologist received the Jan Wolkers Prize, awarded annually by Dutch TV and radio show 'Vroege Vogels'. In his book Schilthuizen describes evolution in one of the newest and most…

Using the MUSE instrument on ESO’s Very Large Telescope in Chile, an international team of scientists, including many Leiden astronomers, have conducted the deepest spectroscopic survey ever. They focused on the Hubble Ultra Deep Field, measuring distances and properties of 1600 very faint galaxies…

Astronomers led by Pieter van Dokkum have discovered a galaxy that barely contains any dark matter, which actually proves that dark matter does indeed exist. The research results will be published this week in Nature.

An international team of astronomers, including Leiden's Maciej Bilicki, has discovered an enormous supercluster of galaxies. The supercluster had previously been overlooked because it was obscured by our own Milky Way. The researchers are publishing their findings in the Monthly Notices of the Royal…

An international team of astronomers that includes researchers from Leiden has discovered the most distant galaxy yet. The galaxy, called EGS8p7, is 13.23 billion light years away from Earth and already existed when the universe was only 550 million years old.

Dark matter represents around eighty per cent of the total mass in the Universe. Yet, we still don't really know what it's made of. Astronomer Pavel Mancera Piña is looking for answers. With a Veni grant from NWO and the most advanced telescopes, such as the James Webb Space Telescope, he will investigate…

Dwarf satellite galaxies in the Milky Way perform different dances than researchers initially expected. Marius Cautun from Durham University received a Marie Curie grant to unravel the mysteries of this orbital dance. October 1st 2018 he will start his research at the Leiden Observatory.

Promotor: H.J.A. Rottgering, Co-Promotor: R.J. van Weeren

One of the key quests in astronomy is to study the growth and evolution of galaxies across cosmic time. Radio observations provide a powerful means of studying the formation of stars and subsequent buildup of distant galaxies, in a way that is unbiased by the presence of dust.

After almost twenty years the record for the most distant radio galaxy has been broken. A team of astronomers led by Leiden PhD candidate Aayush Saxena has discovered a radio galaxy from the time when the universe was just one billion years old. The galaxy is at a distance of 12 billion light years…

An international team of astronomers, with researchers at Leiden Observatory playing a leading role, has mapped the fuel for galaxy formation in the iconic Hubble Ultra Deep Field. The results of the research have been accepted for publication in The Astrophysical Journal.

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…

In 2018, astronomer Jorryt Matthee won the C.J. Kok Jury Prize for the best dissertation of the Faculty of Science. He succeeded in finding a number of rare galaxies from the early Universe. One of them received the same initials as football player Cristiano Ronaldo: CR7.

Promotor: K. Kuijken, Co-Promotor: H. Hoekstra

Within the field of astronomy, understanding how galaxies grow and evolve from the Big Bang to the present day is a challenging and complex question.

Promotor: K.H. Kuijken

The largest galaxies in the Universe feed off cosmic oceans, which helps them grow. This is the presumption of an international team of scientist with two Leiden astronomers, based on observations of the ‘Spiderweb’ galaxy. The researchers published their evidence in Science on 2 December 2016.

Galaxies in the early universe are shrouded in a kind of mist: a cloud of hydrogen. With galaxies in the later universe this mist has disappeared. Astronomer Jorryt Matthee has made the first images of this dissipating mist. PhD defence 19 September.

How do galaxies form? That is what astronomer Mariska Kriek will be researching in the coming years. She received an NWO Vici grant of 1.5 million euros to study galaxies in the early universe. ‘This research uses new and unprecedented observations from the James Webb Space Telescope (JWST). These allow…

Researchers have discovered the most distant Milky-Way-like galaxy yet observed. Dubbed REBELS-25, this disc galaxy seems as orderly as present-day galaxies, but we see it as it was when the Universe was only 700 million years old. This is surprising since, according to our current understanding of…

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…

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…

By looking at stars in dwarf galaxies research Bas Zoutendijk is trying to gain new insight into dark matter.

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…

An international team of astronomers has discovered a large reservoir of hot gas in the cluster-in-formation around the Spiderweb Galaxy. Based partly on that hot gas, the astronomers predict that the cluster-in-formation will grow into one of the largest objects in the universe. A step closer to discovering…

This thesis presents pioneering work on the panchromatic emission of some of the most luminous galaxies in the early Universe: star forming galaxies and active galactic nuclei.

Media all around the world reported about it: the most detailed images yet seen of galaxies, shot by radio telescope LOFAR. The international team behind these amazing results were led by Leah Morabito at Durham University and included three talented Leiden astronomers.

ESA’s Gaia mission has produced the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars and revealing previously unseen details of our home Galaxy.

Finally we know for sure that there is a black hole at the centre of our own galaxy. Today, astronomers unveiled the first ever photo of Sagittarius A*, a super-massive object at the centre of the Milky Way. This picture could only be taken thanks to the cooperation of telescopes worldwide.

Promotor: W. Jaffe, Co-promotor: K. Meisenheimer

Tracing the evolution of the molecular gas content in galaxies is critical for a complete understanding of galaxy formation and evolution, as it provides the direct fuel for star formation. Studies of high-redshift (z>1) molecular gas reservoirs, most commonly traced by carbon monoxide (CO), have seen…

The intracluster medium (ICM) is a hot, tenuous and X-ray emitting gas that pervades galaxy clusters.

Simulations of galaxy formation provide much more information about galaxies than a telescope. Simulations have been improving significantly in recent years. Astronomer Evgenii Chaikin made such a significant contribution to this field that he graduated with honours on February 27th.

An Active Galactic Nucleus (AGN) is a highly luminous region at the center of a galaxy, powered by the accretion into a supermassive black hole and emitting energy from radio waves to gamma rays, often outshining the host galaxy.

Over a seven year period an international team of scientists has mapped more than a quarter of the northern sky using the Low Frequency Array (LOFAR), a pan-European radio telescope. From Leiden, Astronomer Timothy Shimwell and Huub Röttgering, among others, are involved. It reveals an astonishingly…

What’s the fate of our sun, when in 5 billion years from now our Milky Way will clash with the Andromeda Galaxy? Leiden astronomers have been working on calculations on this collision. They recently gave a visual sneak preview on a big tech conference.

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,…

In astronomy, the interpration of observations and measurements plays a crucial role: we rely purely and fundamentally on the information that reaches us as observers. And 80% of all matter in the universe is undetectable directly.

The origin and evolution of galaxies are closely tied to the cyclic feedback processes between stars and the interstellar medium (ISM).

An international team of astronomers has published the most sensitive images of the Universe ever taken at low radio frequencies, using the International Low Frequency Array (LOFAR). ‘LOFAR is unique in its ability to make high-quality images of the sky at metre-wavelengths’, said Huub Röttgering, Leiden…

Promotor: A. Achúcarro Co-promotor: A. Boyarsky