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Gravitational Lensing


Please note that this course description is preliminary. The final course description will be released in June 2019.

Admission requirements

Origins and Evolution of the Universe. Programming skills (eg in python, numpy, matplotlib). Detailed knowledge of General Relativity is not required.


One of the central aspects of General relativity is that light rays are bent by gravity. As a result our view of the Universe is modified, as if we were observing it through a distorting lens. Some parts of the sky are magnified, some are demagnified, and in many cases our view is distorted. The subject of Gravitational Lensing describes this effect. In observational astronomy lensing phenomena can be grouped into three scenarios, known as strong lensing, weak lensing and microlensing, and all will be covered and worked with in the course.

Lectures will provide the background and mathematical description of gravitational lensing, with a focus on the geometrical aspects and the effect of lensing on astronomical observations. take-home exercises will contain a mix of calculations to work with the concepts, as well as computer exercises where the objective is to simulate the effects of gravitational lensing in the various scenarios.

The course consists of four chapters:

  • Introduction
  • Strong lensing: multiple imaging and arcs
  • Microlensing: time variability
  • Weak lensing: small distortions in cosmological observations

Course Objectives

At the end of this course you will understand the concepts of gravitational lensing and its effects on astronomical observations, and show this by knowing how to work with them in real astronomical observations.

At the end of this course, you can:

  • Explain the fundamental lensing equations
  • Recognize the difference between strong, weak and micro lensing
  • Predict the effect of lensing on astronomical observations
  • Quantitatively analyze gravitational lensing observations

Soft Skills

This is a technical course that requires detailed work and understanding. You will practice independent working and critical self-assessment through computer modelling of gravitational lensing systems, in the computer language of your own choice. You are required to prepare by reading relevant chapters of the course material before the lectures.


See Astronomy master schedules

Mode of Instruction

  • Lectures

  • Exercise classes where homework is discussed

  • Lecturer and teaching assistant will be available during office hours

Assessment Method

  • Homework assignments: 40% of final grade (average >= 6 as requirement to take oral exam)

  • Oral exam: 60% of final grade (only open to students who handed in homework exercises)

The final grade is either the exam grade, or a 60/40 weighted average of the exam and homework grades, whichever is higher.


Blackboard is not used in this course.

Reading list



Via uSis. More information about signing up for your classes can be found here. Exchange and Study Abroad students, please see the Prospective students website for information on how to apply.

Contact information

Lecturer: Prof.dr. K. (Koen) Kuijken
Assistant: To be announced
Course website: To be announced