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Radiative Processes


Admission requirements

None. The course requires basic knowledge of electromagnetism and special relativity, but these concepts will be briefly reviewed.


Our knowledge of the universe is mainly indirect, mediated by the light we receive on earth from the objects in the sky. Therefore, to understand how objects like planets, stars and galaxies work, we need a physical understanding of how their observed light is produced.

We will define a number of fundamental concepts necessary to unambiguously discuss radiation. This is followed by the introduction of the basic equation of radiative transfer, which describes how radiation changes as it traverses a medium. In the remainder of the course we will keep coming back to this equation. This part will be concluded with a discussion of a few methods to solve the equation of radiative transfer.

Then we take a step back and examine the relation between the concepts introduced earlier. We will find that radiation can only be generated and changed by accelerating electrical charges, and we will deduce several fundamental relations.

This is followed by a discussion of three important mechanisms to produce continuous radiation, i.e., radiation that changes only weakly with wavelength.

All these processes involve freely moving electrons: in an ionized plasma (Bremsstrahlung or free-free emission); in the presence of magnetic fields (cyclotron and synchrotron emission, depending on whether the electrons move non-relativistically or relativistically); and the interaction between relativistic electrons and photons (inverse Compton scattering).

We will conclude the lecture series with the production of radiation at discrete wavelengths, i.e. spectral lines. These processes involve electrons bound to atoms or molecules.

Course objectives

The goal of this course is twofold. First, to comprehend how light interacts with matter and how matter can convert different kinds of energy into light. Second, to learn how to extract physical information about the emitter (e.g. size, temperature and composition) from observations.

Soft skills

In this course, students will be trained in the following behaviour-oriented skills:

  • Problem solving (recognizing and analyzing problems, solution-oriented thinking)

  • Analytical skills (analytical thinking, abstraction, evidence)

  • Critical thinking (asking questions, check assumptions)

  • Creative thinking (resourcefulness, curiosity, thinking out of the box)


See Schedules bachelor Astronomy 2017-2018

Mode of instruction

  • Lectures

  • Exercise classes

Assessment method


Lecture notes, additional readings and assignments will be provided through Blackboard.
For Blackboard access, you need an ULCN account. More information:

Reading list

  • Radiative Processes in High Energy Astrophysics, Ghisellini, ISBN 9783319006123, download here (required)

  • Radiative Processes in Astrophysics, Rybicki & Lightman, ISBN 9780471827597 (recommended)


Register via uSis. More information about signing up for classes and exams can be found here. Exchange and Study Abroad students, please see the Prospective students website for information on how to register. For a la carte and contract registration, please see the dedicated section on the Prospective students website.

Contact information

Lecturer: Prof. Dr. Huub Röttgering
Assistant: Hiddo Algera, Tommaso Marchetti
Course website: Radiative Processes