ASTROPHYSICS

This course deals with fundamental aspects of modern Astrophysics and gives the student the possibility of mastering them for the application to research, public outreach, and education in fields of the Science of the Universe. The lectures focus on the theory of the formation of stars and planetary systems, and stellar structure and evolution. They outline basic concepts and applications that have also wide implications for Galactic Astronomy and Cosmology.

Knowledge and understanding. The main goal of the course is to provide the student with a discriminating knowledge of stellar and planet formation mechanisms, of stellar structure and evolution from first principles. The acquisition of discriminating knowledge about the connections to related fields is also part of the course’s objectives.

Applying knowledge and understanding. The course allows the student to acquire skills in identifying the essential elements of astrophysical phenomena, in terms of order of magnitude and necessary approximation level, and in applying the necessary approximations. The student will also be capable of identifying the common theoretical framework amongst different areas and use analogy arguments to apply known solutions to new problems and different astrophysical contexts.

Making judgements. Students will gain the skills needed to compare observational data with theoretical models and plan experiments, if only at a conceptual level, aiming at revealing possible deviation from the models’ predictions.

Communication skills. The course gives the student the possibility of acquiring specific competences for a correct and effective communication of astrophysical topics.

Learning skills. The student can acquire adequate cognitive methods for a continuous update of Astrophysical subjects and the capability to access to the specialised literature in Astrophysical and related fields.

The main concepts are taught in front lectures, which include practical examples. Learning effectiveness is monitored through written exercises and intermediate tests.

Should the circumstances require online or blended teaching, appropriate modifications to what is hereby stated may be introduced, in order to achieve the main objectives of the course. Exams may take place online, depending on circumstances.

Information for students with disabilities and/or learning disabilities (LD). To ensure equal opportunities and in compliance with applicable laws, interested students may request a personal interview to plan any compensatory and/or dispensatory measures, based on their educational objectives and specific needs. Students may also contact the CInAP (Center for Active and Participatory Integration - Services for Disabilities and/or LD) contact teacher in the Department of Physics. 

Important knowledge: Atomic Physics. Nuclear Physics.

Attendance is compulsory according to the rules of the teaching regulations of the CdS in SFA as reported in the link:

http://www.dsf.unict.it/corsi/l-29_sfa/regolamento-didattico

FUNDAMENTALS OF STELLAR STRUCTURE AND EVOLUTION. Reference frames, mass distribution, and gravitational fields in spherical symmetry. Eulerian and Lagrangian description. Conservation of momentum. The virial theorem. Conservation of energy. Energy transport. Dynamical instabilities. Convection. Chemical composition. Equations of stellar evolution. The equation of state of stellar matter. Opacity. Nuclear energy production.

MODELS OF STELLAR STRUCTURE. Polytropes. Chandrasekhar mass limit. Isothermal spheres. Homology relations. The zero-age main sequence. The Hayashi track. Dynamical stability.

FORMATION OF STARS AND PLANETS. Gravitational instability. Collapse of a spherical cloud. Contraction toward the main sequence. Characteristics of pre-main sequence stars. Accretion phenomena and the formation of planetary systems.

STELLAR EVOLUTION. Evolution on the main-sequence. Evolution though helium burning. Evolution in the asymptotic giant branch. Advanced stages of core evolution. Final explosions and collapse.

COMPACT OBJECTS. White Dwarfs. Neutron Stars. Black Holes.

STELLAR OSCILLATIONS AND ASTEROSEISMOLOGY. Radial and non-radial oscillations of stars. Principles and applications of asteroseismic models.

[1] Kippenhahn R., Weigert A., Weiss A., “Stellar Structure and Evolution”, 2nd edition, Springer-Verlag 2012

[2] T. Padmanabhan, “Theoretical Astrophysics”, Cambridge University Press, 2001

[3] Stahler S.W., Palla F., “The Formation of Stars”, Wiley-VCH, 2005

[4] A. Lanzafame, "Notes on the Astrophysics course", 2025

[5] Sarbani Basu & William J. Chaplin, "Asteroseismic data analysis - Foundation and techniques", Princeton series in modern observational Astronomy, 2017

The final exam consists of an oral exam.

Written tests may be administered as part of the learning assessment, but they do not contribute to the final grade.

The oral exam consists of a discussion of three topics covered during the course, one of which the student will choose. The clarity of the presentation, logical rigor, mastery of the topic, and the ability to apply the concepts learned to specific cases will be assessed.

The learning assessment may also be conducted online, if circumstances require it.

The questions below are not an exhaustive list but rather a few examples.

What are the stability conditions of an isothermal spherical cloud?

What are the differences between the main-sequence evolution of low- and high-mass stars?

How is the Jeans mass calculated?

What are the relevant timescales of stellar evolution?

What the Hayashi track is?

How the Chandrasekhar mass limit can be calculated?

How a neutron star forms?

What are the physical mechanisms of the thermal pulses in the asymptotic giant branch?

What are the fundamental physical phenomena in a supernova core collapse?

What "helium flash" means?