96387 - Stellar Evolution

Learning outcomes

The aim of this course is to give a specialistic overview of the stellar evolution theory for stars with different masses. In particular the student will understand how the main physical properties of stars with different masses change as a function of the age, how these changes are related to the thermonuclear evolution of each star, which are the final stages of star life, which are the properties of the remnants. The student will also get a general view of the open issues in the field of the stellar evolution research.

Course contents

The time scale of stellar evolution. Evolution tracks and isocrhrones. Jeans Mass. Pre-Main sequence evolution. Hayashi tracks. The core hydrogen-burning phase. The stellar structure along the Zero Age Main Sequence. Isothermal core properties and the Shomberg-Chandrasekhar criterion. Post-Main sequence evolution. Envelope expansion. Sub-Giant and Red-Giant phases. The first Dredge-up. General properties of stars along the RGB: RGB-Bump and the development of a degenerate Helium core in low mass stars. The Helium flash. The Zero Age Horizontal Branch and the observational properties of the Horizontal Branch. Convection and the overshooting problem. The semi-convection theory. Double shell burning phase. The Asymptotic Giant Branch phase. The element production in the AGB. The second and third dredge-up. Pulsating stars. The period-luminosity relation. The k-mechanism and the location of partially ionized regions inside the stars. Pulsating variables: Cepheids and RR Lyrae. The final stages of stellar evolution. White Dwarf properties. The WD cooling sequence. The Chandrashekar mass.

Supernovae: Type II (core-collapse) and Ia (thermonuclear). Supernovae: progenitors, time scales, ejecta and remnants. Overview of the formation of the chemical elements in the Universe.

The structure of compact stellar remnants: Neutron stars (NS). Pulsar. Millisecond-Pulsar. Black Holes (BH). Gravitational waves (GW)- basic concepts – determination of the mass of a GW emitting system - GW from BH-BH and NS-NS systems – Kilonovae- explosive nucleosysnthesis and formation of heavy elements

Readings/Bibliography

The final exam can be pepared using the notes taken during the lessons and the Lecture Notes made available by the teacher every year at the site "Virtuale UniBo" of the Bologna University.

However, the attending in person to the course is strongly reccommended for a successful acquisition and understanding of the topics. In addition students will have the opportunity to ask questions during the lessons, for a full comprehension of the topis. Additional textbooks for further deepening the specific topics are:

Evolution of stars and stellar populations - Salaris & Cassisi

An Introduction to modern Astrophysics - Carroll & Ostlie

Astrophysics I. stars - Bowers & Deeming

A good introduction to the course can be found in this book (unfortunately only in italian):

F.R. Ferraro - Figli delle stelle - 2024 (Bietti, Milano)

Teaching methods

Class Lecures are presented by using power-point presentations. The lessons provide explanation of the astrophysical stellar concepts also supported by images, graphs and videos aimed at improving the comprehension.

Assessment methods

The oral examination consists in a series of questions aimed at verifying that the student has a correct picture of the main evolutionary properties of low and high-mass stars. It typically lasts 40-45 minutes.

The final grade will be set based on the following scheme:

• grade=18-21: the knowledge is limited to just a small sub-sample of topics and the student answers to the questions only with a substantial help from the teacher
• grade=22-25: the knowledge concerns a larger number of topics, and the student answers the questions with some teacher help
• grade=26-28: the student is able to discuss most of the topics and answer the questions with good autonomy and critical sense, showing some uncertainties only on second-order points.
• grade=29-30L: the student shows solid and deep knowledge and excellent understanding of all the topics, answering to all questions readily and with very good mastery of the scientific terminology

During the exam, students are not allowed to use notes and books.

The student has the opportunity to refuse the assigned grade at most 2 times. Then, the last obtained grade (not the best one) will be registered.

Students with special needs are recommended to contact in advance the dedicated UniBO service (https://site.unibo.it/studenti-con-disabilita-e-dsa/en ).

Teaching tools

Lectures are performed with power-point presentations. The slides are updated and made available to the students every year on the dedicates web site "Virtuale uniBO" of the Bologna University

Office hours

See the website of Francesco Rosario Ferraro