2023-2024 / SPAT0006-1

Stellar atmospheres


20h Th, 10h Pr

Number of credits

 Master in space sciences (120 ECTS)3 crédits 


Grégor Rauw

Language(s) of instruction

English language

Organisation and examination

Teaching in the second semester


Schedule online

Units courses prerequisite and corequisite

Prerequisite or corequisite units are presented within each program

Learning unit contents

Stellar spectra are formed in the stellar atmospheres and they contain a wealth of information on the physical conditions in these atmospheres. The goal of this course is to establish the link between the physical parameters on the one hand and the observable quantities (i.e. the spectra) on the other hand.
The course starts by reviewing the link between the Hertzsprung-Russell diagram and the stellar spectra. Next, we introduce the main classification criteria that are used to assign a spectral type directly from the observations. We then recall the fundamental notions of the interaction between matter and radiation and we introduce the concept of radiative transfer both in static and moving atmospheres. We introduce stellar atmosphere models aiming at the calculation of synthetic stellar spectra. We discuss the various assumptions (hydrostatic equilibrium, local thermodynamical equilibrium or absence of the latter) that affect the opcaities of matter in the stellar atmosphere. We then review the various effects that determine the aspect of spectral lines (intrinsic width, Doppler and pressure broadening, rotational velocity, chemical composition). The modeling of expanding atmospheres (stellar winds) is also addressed. Finally, we consider the issue of stellar magnetic fields and their impact on the light and its polarization.

Learning outcomes of the learning unit

The purpose of this course is to explain the link between physical parameters of the stars and the characteristics of the light they emit. Upon completion of this course the students will be able to understand how stellar properties such as the temperature, the luminosity, the chemical composition,... can be inferred from the analysis of stellar spectra.

Prerequisite knowledge and skills

Good knowledge of physics and mathematics.

Planned learning activities and teaching methods

Several tutorial (exercise) sessions are organized to illustrate the concepts introduced during the lectures.

Mode of delivery (face to face, distance learning, hybrid learning)

Blended learning

Additional information:

About 22 hours of theoretical lectures + 8 hours of tutorial sessions. The course takes place during the second semester. The majority of the lectures will be delivered face-to-face (sanitary conditions permitting), but some lectures could also be provided as podcasts.

Recommended or required readings

The lecture notes and a copy of the slideshow are provided in English through a pdf file available on the eCampus website of the course.

All these documents are made available exclusively to the students of this course for a strictly personal and private use, and shall not be shared with a third party. Furthermore, it is forbidden to submit these documents to an artificial intelligence or to an artificial intelligence-powered language model. This restriction equally holds if the goal of such a submission would be to generate a summary for personal use.


Exam(s) in session

Any session

- In-person

written exam ( open-ended questions )

Additional information:

The evaluation emphasizes the understanding of the course and the ability to use the techniques that have been taught. To successfully pass the exam students have to learn and understand the course. The assessment is based on a written exam consisting of theory questions and exercises.
The exercise part is open book, meaning that the student can use papercopies of the official notes as well as personal notes. The use of electronic devices, tablets, smartphones or similar during the exam is forbidden.

Work placement(s)

Organisational remarks and main changes to the course



Prof. Gregor Rauw Institut d'Astrophysique et Géophysique, Bât. B5c Allée du 6 Août, 19c 4000 Liège
Tel. +32-(0)4 366 9740 e-mail: g.rauw@uliege.be

Association of one or more MOOCs