Universiteit Leiden

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Galaxies and the structures in which they are embedded

Researchers at Leiden Observatory study the fundamental physics that creates structure in the Universe. These processes collect matter into galaxies and gas into stars. With the use of powerful telescopes and advanced calculations and computer simulations, Leiden astronomers seek to understand the origin, structure and evolution of galaxies in general, and the Milky Way galaxy in particular. Through these structures the unknown physics is uncovered of the dark matter and dark energy that takes up 95% of the Universe.

Soon after the Big Bang, gravity started to form structure in a Universe dominated by dark matter and dark energy. ‘Normal’ (baryonic) matter collected into observable building blocks known as galaxies. Leiden astronomers are driven by the question how fundamental physical processes give rise to this structure, how galaxies form and evolve, what their structure and dynamics is, and how galaxies turn matter into stars. Why are some galaxies given over to bursts of star formation while others linger and retain large amounts of primordial gas? Why is it that most galaxy centers seem to harbor massive black holes? And how does the energy released by matter accreting onto these black holes affect the evolution of the host galaxy and the space around it? How do galaxies, through the stars they form, enrich the gas inside and around themselves with elements heavier than helium? At Leiden Observatory, galaxies are studied in the nearby Universe and in the far-away and early Universe. Our own Milky Way galaxy offers the possibility to investigate an ‘average’ galaxy up close, and seek to understand how its stellar population and dark matter content was acquired and how the massive black hole at the Milky Way’s center shapes its environment.


Staff members of Leiden Observatory study these topics within their research programs and collaborations related to large-scale structure and cosmology, galaxies and active galactic nuclei, interstellar matter, and computational astrophysics. They have access to the world’s most powerful telescopes, such as VLT, ALMA, LOFAR, HST, Gaia, Chandra and XMM-Newton, and upcoming facilities such as E-ELT, JWST, Euclid, and SKA. Instrumentation development at Leiden Observatory provides key technology enabling breakthrough observations with these facilities. Multi-wavelength/spectroscopic large-scale surveys and deep observations are analyzed using staff expertise in gravitational lensing, stellar population synthesis, astrometry, galactic dynamics and molecular astrophysics. Massive computer simulations recreate the growth of black holes and dense star clusters, as well as the formation of structure and galaxies in large slices of the Universe. This dialogue between groundbreaking observations and theory / simulations is the hallmark of research at Leiden Observatory into galaxies, their surroundings, and the structure of the Universe.