a list of offered projects

There will be several PhD positions open for application

with a deadline of November 15, 2025 . For details of the application procedure see this page . The PhD positions that are offered this round are listed below.

The faculty research interests provides more background information about the research conducted at the Leiden Observatory.

PhD project 1: Using optical metamaterials to create hybrid coronagraphs

Description: Imaging Earth-like planets is challenging due to the overwhelmingly large difference in brightness between a planet and its host star. Coronagraphs are specialized optical systems that filter out this star light to reveal faint exoplanets. However, any instrumental error will cause light from the star to leak through the system creating speckles that difficult to distinguish from planet light. We will leveraging optical metamaterials, an exciting new class of optical components, to develop hybrid coronagraphs that both act as a coronagraph and as a wavefront sensor. This will allow us to measure the deformations in starlight and use active control to remove the deformations. Optical metasurfaces, constructed with nanoscale structures using advanced lithographic techniques, provide unparalleled manipulation of their optical characteristics. This capability allows them to surpass previous limitations in the design of coronagraph components. In this project the applicant will work together with Dr. Sebastiaan Haffert to develop optical meta-material components for the Extremely Large Telescope (ELT). The new technology will be tested on-sky at world-leading observatories to demonstrate their potential for the ELT.

PhD project 2: Dissecting the complexity of Planetary Nebulae in 3D

Galactic Planetary nebulae (PNe), the final evolutionary stages of stars with initial masses between 0.8 and 8.0 M☉, play a key role: i) in our understanding of last stages of the stellar evolution; ii) in the (re)cycling in ISM of processed material within the stars, and by extension the chemical evolution of the Galaxy (and the Universe); iii) as self-contained laboratories to study the physics of ionised plasmas, thus acting as corner-stone targets for our study of the ISM in its broadest sense; iv) as templates for extra-galactic PNe to understand the properties of galaxies other than ours.

PNe are far from simple entities. They exhibit different levels of symmetry, and within a single PN, a wide range of structures may be found with varying degree of ionisation, density, size, shape and composition. In this sense, the information collected by traditional techniques can be misleading since they sample only a small subset of the existing ions (narrow filter imaging) or selected portions of the nebula (long-slit spectroscopy). A handful of studies of individual targets have demonstrated that Integral Field Spectroscopy is able to capture this richness in terms of structure, and physical and chemical properties. However, we are just seeing the tip of the iceberg: there is a need for a spatial-spectral study making use of high-quality data for a sample of PNe, covering a representative range of morphologies, abundances, ages and stellar masses. This project aims to fill this gap. In this project, the student will unveil the hidden complexity of planetary nebulae in 3D by using the state-of-the-art spectroscopic instrumentation in astrophysics. It will be possible reveal previously unknown structures within the studied PNe and map their physical and chemical conditions in 2D. The data gathered will provide the most complete description of a PN and its multiple phases, allowing us to recover the full picture of the PNe with unprecedented detail through 3D photoionization modeling.

PhD project 3: Next steps in the characterisation of exoplanet atmospheres

Characterisation of exoplanet atmospheres is going through a rapid revolution. JWST is transforming our understanding of increasingly smaller and cooler planets. Soon the Extremely Large Telescope will see first light that will move the field even further. In this PhD project, you will work with state-of-the-art techniques, such as spectral filtering, cross-correlation methods, and molecular mapping on either space-based or groundbased data, or both. We are slowly but surely pushing towards planets that could be like Earth and find out what they are like.

PhD project 4: The molecular ISM at high-redshift

Tracing the evolution of gas in galaxies is critical for a complete understanding of galaxy formation. Recently, huge strides have been made on this front both observationally and theoretically. And yet, most observations of distant (z>1) galaxies still rely on high-J CO emission lines, which are known to give a biased and incomplete view of the total molecular gas reservoir. In this project, we will use recently awarded observations on the VLA/ALMA, as well as ultimately ALMA Bands 1 & 2, to directly detect and resolve the critical low-J CO (and [CI]) lines in a significant sample of z~2-5 galaxies. Specifically, we will: 1) Obtain robust total molecular gas masses, gas fractions, and consumption timescales, free from excitation bias; 2) Calibrate alternative cold gas mass tracers including long-wavelength dust continuum, [CI], and [CII]158μm emission in galaxies spanning a range of redshifts and physical conditions; and 3) Combining with JWST observations & resolved follow-up, provide the first high-resolution, multi-tracer view of the stellar mass (past), star formation (present), and cold gas (future) of individual high-redshift galaxies with which to test the latest hydrodynamical simulations that resolve cold gas in high-z galaxies (eg COLIBRE).

PhD project 5: Cosmic-Ray Acceleration and Radio Filaments in Galaxy Clusters with LOFAR2.0

Galaxy clusters are the largest virialized cosmic ecosystems in the Universe—and they also act as gigantic particle accelerators. In addition to galaxies and dark matter, clusters are filled with hot plasma, magnetic fields, and cosmic rays: highly energetic particles that emit synchrotron radiation detectable with modern radio telescopes. A key open question is how these cosmic rays are accelerated and how they interact with the surrounding plasma. Recent observations have also revealed puzzling, extremely narrow filamentary radio sources in clusters, whose origin remains unknown.

This PhD project will exploit the revolutionary capabilities of the upgraded LOFAR2.0 radio telescope to tackle these questions. LOFAR2.0 opens a new observational window at ultra-low frequencies, enabling us to probe the lowest-energy cosmic rays—the bulk of the cosmic-ray population—for the first time. By combining LOFAR2.0 data and advanced computational methods with complementary higher-frequency radio observations, the project will deliver deep, high-resolution maps of galaxy clusters and study the physical processes responsible for cosmic-ray acceleration and filamentary radio structures.

PhD project 6: Chemical abundances and the stellar initial mass function in massive quiescent galaxies over cosmic time

In recent years, it has become clear that massive galaxies formed and evolved much faster than predicted, with many already mature when the Universe was only a fraction of it current age. Yet we still lack a clear understanding of how these galaxies assembled so rapidly, and how massive they truly are. A PhD position is available in the group of Prof. Mariska Kriek to study the chemical abundances and stellar initial mass function of massive quiescent galaxies across cosmic time, primarily using data from the James Webb Space Telescope. The PhD candidate will analyse ultradeep spectroscopic data and contribute to the development of new tools and techniques for their interpretation. This research will provide new insight into the chemical enrichment and formation histories of massive galaxies, and help determine their true masses.

PhD project 7: Resolving Galaxies over