Exoplanets close in to their host star receive high levels of extreme ultraviolet (EUV) irradiation, capable of heating and ultimately driving the hydrodynamic escape of their atmospheres.

Over the past years it has been discovered that the population of extra-solar planets is large and diverse.

More than 5,000 exoplanets have been found over the past couple of decades. These exoplanets show a tremendous diversity, ranging from scorching hot Jupiters, common super-Earths, to widely separated super-Jupiters on the planet/brown dwarf boundary.

This thesis investigates the evolution and fate of gaseous exoplanets, which are continuously shaped by stellar activity across both short and long timescales.

This thesis describes the implementation and on-sky demonstration of high-resolution integral-field spectroscopy for extreme adaptive optics systems that are used to find and characterize exoplanets.

At Leiden Observatory, researchers investigate the origin of stars and their planetary systems. They detect and characterize planets around other stars (exoplanets). They study how stars and planets form. And they follow molecules from interstellar clouds to nascent planet systems. This way they address…

At Leiden Observatory, researchers investigate the origin of stars and their planetary systems. They detect and characterize planets around other stars, which are called exo-planets. They study how stars and planets form. And they follow molecules from interstellar clouds to nascent planet systems.…

This thesis describes the Multi-site All-Sky CAmeRA (MASCARA), which consists of two small robotic telescope designed to detect exoplanets around the brightest stars in the sky.

Understanding the formation and evolution of planetary systems is one of the most fundamental challenges in astronomy. To directly image and study young exoplanets and the circumstellar disks they form from, dedicated high-contrast imaging instruments are built.

One of the key discoveries in exoplanet research over the past decade is the abundance of small planets in our Milky Way. Despite their high numbers, our understanding of their atmospheres remains limited, and it is unknown if they possess atmospheres at all.

One of the key limitations of the direct imaging of exoplanets at small angular separations are quasi-static speckles that originate from evolving non-common path aberrations (NCPA) to which the primary adaptive optics system is inherently blind. The main focus of this thesis is the development and…

Promotores: Prof.dr. C.U. Keller, Prof.dr. H.C. Gerritsen

Promotor: C.U. Keller, Co-Promotor: F. Snik

The next generation of high-contrast imaging instruments on space-based observatories requires sophisticated wavefront sensing and control in addition to a high-performance coronagraph.

This thesis describes the development and validation of new high-contrast imaging techniques, with the ultimate goal of enabling the next generation of instruments for ELT-class telescopes to directly image Earth-like extra-solar planets orbiting around nearby stars.

Promotor: Christoph U. Keller, Co-promotores: Matthew A. Kenworthy, Frans Snik

Dutch astronomers have measured a superstorm for the first time in the atmosphere of an exoplanet, the well-studied “hot Jupiter” HD209458b. The very high-precision observations of carbon monoxide gas show that it is streaming at enormous speed from the extremely hot day side to the cooler night side…

How did we come into existence? Are we alone? These questions have driven humans for centuries.

Astronomers at Leiden University have discovered the first planets using a new instrument: the planet hunter MASCARA. This instrument, developed at Leiden Observatory, looks specifically for planet transitions around the brightest stars in the sky, which surprisingly enough have so far have hardly been…

This thesis aims to demonstrate how the achromatic nature and design flexibility of liquid-crystal optics can be used to improve high-contrast imaging instruments to facilitate detailed exoplanet characterization.

An international team led by Leiden astronomers has, after years of searching and defying the boundaries of a telescope, for the first time directly captured polarised light from an exoplanet. From this light they can deduct that a disk of dust and gas orbits the exoplanet. In this disk moons are possibly…

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 James Webb Space Telescope has found evidence of carbon dioxide (CO₂) in the atmosphere of a giant planet 700 light years away. This result provides insight into the composition and formation of this gas giant and shows what James Webb is capable of. The research by the international group of astronomers,…

Two Leiden scientists - Ignas Snellen and Bernhard Hommel - have been awarded an ERC Advanced Grant. The grant will fund their research over the coming five years on exoplanets and free will.

Researchers from Japan and the Netherlands who were previously involved in the discovery of an exoplanet with huge rings have now calculated that the giant rings may persist more than 100,000 years, as long as the rings orbit in the opposite direction to that of the planet around the star. Their findings…

Promotor: Prof.dr. I.A.G. Snellen, C.U. Keller

Astronomers from the Leiden Observatory and from the University of Rochester (in the US) have discovered that the planetary ring system that covered the very young sun-like star J1407 is actually of enormous proportions. In fact, it’s much larger and heavier than the ring system surrounding Saturn.…

This thesis addresses the chemical processes that determine the compositions of giant planet atmospheres.

Over the last three decades, the discovery of exoplanets has revealed the boundless variety of worlds beyond our own Solar System⁠. Majority of planetary systems contain short-period planets that are larger than Earth but smaller than Neptune⁠.

Leiden University has participated in an international study carried out by the CARMENES consortium, which has discovered two small, terrestrial planets around Teegarden’s Star. The planets have masses similar to Earth and their temperatures could be mild enough to sustain liquid water on their surf…

An international team of astronomers have become the first in the world to detect isotopes in the atmosphere of an exoplanet. It concerns different forms of carbon in the gaseous giant planet TYC 8998-760-1 b. The research will be published in the scientific journal Nature on Thursday.

Using the Dutch-led Low Frequency Array (LOFAR) radio telescope, astronomers have discovered unusual radio waves coming from the nearby red dwarf star GJ1151. The radio waves bear the tell-tale signature of aurorae caused by an interaction between a star and its planet. The radio emission from a star-planet…

Promotor: I. A. G. Snellen, Co-promotor: M. A. Kenworthy

Hot rocky exoplanets are planets that orbit so close to their host star that they possess a molten surface.

One unravels the origin of the largest black holes in the universe, the other investigates the influence of stellar wind on the atmosphere of exoplanets. Both Elena Maria Rossi and Aline Vidotto receive a Vici grant for their research into the mysteries of the universe. ‘I have no idea yet how we can…

Detecting planets during their formation stages is crucial for understanding the history and diversity of fully developed planetary systems like our own. However, observing young planets directly is challenging because they are often deeply embedded within their host protoplanetary discs, rich in gas…

The zoo of detected exoplanets reveals both the uniqueness of our own Solar System and the complexity of planetary system formation, sparking fundamental questions about how planetary systems form and evolve.

Diverse types of exoplanets such as gas giants on close-in orbits (hot Jupiters) and young massive giants on wide orbits (super Jupiters), with no analogs in the Solar System, pose challenges but also opportunities to our understanding of planet formation and evolution.

Even though more than 4000 extra-solar planets are known today, only a small fraction of these has been captured in an image. To better understand the planet formation mechanisms in solar-like environments we started the Young Suns Exoplanet Survey (YSES).

If there is life outside our galaxy, how could we find it? In his Oort Lecture, James Kasting talks about his search for simple life on other planets. Kasting was in the Netherlands for two weeks, because he was invited as the Oort Professor 2018.

Promotor: Prof. dr. I. Snellen, Co-Promotor: Dr. M. Kenworthy

A remarkable population of short period transiting rocky exoplanets with equilibrium temperatures on the order of 2,000 K has recently been discovered.

Is there extra-terrestrial life out there? It now looks as though we can sketch out an answer to this enduring question. Leiden Observatory is helping to build new instruments to find the most promising exoplanets.

Research at Leiden Observatory spans the full width of modern astrophysical enquiry. It is based on observation, theory, simulation, and experiment. Two broad clusters characterize the ongoing research. Within each theme, researchers carry out their personal and specialized research programme. The two…

The field of exoplanet research is rapidly advancing through the development of new technology, observing techniques, and post-processing methods.

This thesis focus on the interaction between M dwarf stellar winds and Galactic cosmic rays and the possible effects on the habitability of exoplanets.

Until the 1990s, the only known planets were those in our Solar System. Three decades later, several thousand exoplanets have been discovered orbiting stars other than the Sun, and substantial efforts have been made to explore these strange new worlds through spectroscopic analyses of their atmosphe…

Northern lights, stellar winds and exoplanets. This is what astronomer's PhD research revolved around. PhD candidate astronomer Rob Kavanagh developed mathematical models to better understand the interactions between exoplanets and stellar winds and to define features of exoplanets. He will receive…