Duration
20h Th, 10h Pr
Number of credits
| Master in space sciences (120 ECTS) | 3 crédits |
Lecturer
Language(s) of instruction
English language
Organisation and examination
Teaching in the second semester
Schedule
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. Stellar atmosphere codes aiming at the calculation of synthetic spectra rely on a number of assumptions (hydrostatic equilibrium, local thermodynamical equilibrium or absence of the latter) and we discuss these different hypotheses. 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 their spectra. 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 (atomic spectroscopy) 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)
About 22 hours of theoretical lectures + 8 hours of tutorial sessions. The course takes place during the second semester. In 2021, the course is given remotely via the Lifesize tool.
Organisational adjustments related to the current health context
In case of a (partial) re-confinement due to the Covid-19 pandemic, lectures will be given remotely via podcasts recorded with Camtasia and skype or Lifesize sessions. The details of the exercises and other mathematical developments that would normally be presented on the blackboard will be provided as pdf files on eCampus.
The examen will take place on the campus (except in case the autorithies would stipulate that all exams must take place remotely) as a written exam (duration of 3h max.). The exam contains a theory question (closed book), a spectral classification (open book) and an exercise (also open book).
In case all exams would be organized remotely, the exam will be organized remotely via Lifesize or skype and includes (1) a theory question to be answered orally, (2) an exercise (resolution on a sheet of paper and photograph of the resolution to be sent by e-mail), and (3) a spectrum to be classified (argumentation to be sent by e-mail).
Recommended or required readings
The lecture notes are provided in English through a pdf file available on the eCampus website of the course.
Assessment methods and criteria
Below you will find information on the evaluation methods planned for in-person and remote exams as well as those planned for hybrid sessions. Depending on how the health crisis evolves, the chosen method will be communicated to you no later than one month before the start of the exam session.
Any session :
- In-person
written exam ( open-ended questions )
- Remote
written exam ( open-ended questions ) AND oral exam
- If evaluation in "hybrid"
preferred in-person
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.
Work placement(s)
Organizational remarks
N/A
Contacts
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