The goal of the Course is to present an overview of several developments in modern astrophysics, with special emphasis on the role played by measurements and observations in the progress made. The course is taught by four scientists in a coordinated manner. After a general part, focused on the problem of dark matter, one part of the course is devoted to observations and concepts related to compact objects and black holes, a short part to the cosmological framework, and a final part devoted to measurements close to particle physics. The main points of interest are raised by the following very general questions. What is the nature of research in astrophysics? What are the most important results of modern astrophysics? What is the connection between progress in astrophysics and progress in technology and instrumentation? The course "Introduction to Astrophysics" tries to give a first answer to these questions. The goal is to offer to the students the opportunity to get to know the approach and the mind framework of astrophysicists and, by means of key examples, an overview of several interesting lines of research in modern astrophysics.
Expected learning outcomes
At the end of the course, the student will master the following skills:
Will know the basic language, the main results obtained so far, and the most important technological and observational initiatives in relation to the key areas of astronomical research (optical, radio, x-rays, etc). Will be able to formulate a dynamical model suited to identify and quantify the possible presence of dark matter in different contexts (in particular, spiral galaxies and clusters of galaxies). Will be able to interpret and to model, broadly speaking, phenomena related to the presence of massive and supermassive black holes. Will be able to evaluate, broadly speaking, the importance of the main areas of research in astroparticle physics (solar and extrasolar neutrinos, cosmic rays, gamma rays, the search of dark matter candidates).
1.1 Sources of astronomical information and general picture of the physical processes responsible for the various kinds of observed emission. Electromagnetic radiation, particles, gravitational waves. 1.2 Highlights on the modern astrophysical framework. Progress as confrontation between models and measurements; role of "decisive measurements". Observations from the ground and from space. Optical astronomy. Radioastronomy. X-ray and gamma-ray astronomy. Neutrinos. Space physics. The discovery of galaxies, as a landmark example in astrophysics of the 20th century and as a bridge between "small scale" astronomical systems and cosmology. General properties of galaxies: scales and some basic physical characteristics. 1.3 The problem of dark matter. Tools to weigh light sources observed by telescopes. The supermassive black hole at the center of our Galaxy. The problem of the thickness of our Galaxy. 1.4 Virial theorem and early applications to clusters of galaxies. Application of the model of hydrostatic equilibrium to the X-ray emission from galaxy clusters. 1.5 The problem of dark matter in spiral galaxies. Rotation curves and their decomposition into disk and halo contributions. 1.6 Cosmological impact, gravitational lenses, very short introduction to MOND (Modified Newtonian Dynamics).
PART 2 (G. Lodato 10 hours)
2.1 Black holes in astrophysics: mathematical description and physical properties: mass and spin. Characteristic length scales. Black holes as energy sources: efficiency and Eddington luminosity. 2.2 Supermassive black holes in galactic nuclei. Scale relations. Active Galactic Nuclei and their phenomenology. 2.3 Stellar-mass black holes. X-ray binaries: observed properties. State transitions and QPO (Quasi-Periodic Oscillation). 2.4 Transient phenomena: gravitational and their sources. Tidal disruption of stars.
Part 3 (L. Guzzo 4 hours)
3.1 The cosmological scenario: general introduction to the relevant observations and measurements. 3.2 The cosmological scenario: hot Big Bang and structure formation.
PART 4 (B. Caccianiga 12 hours)
4.1 Strategies for the detection of particles of astrophysical origin. Neutrinos, gamma rays, cosmic rays. Cherenkov effect and fluorescence. Highlights on the main types of detectors. Photomultipliers, bolometers, solid-state detectors. 4.2 Measurements of solar neutrinos and supernova neutrinos. Comments on the astrophysical problems that motivate these measurements. Objectives and results of neutrino experiments (Gallex, Homestake, Superkamiokande, Borexino, SNO,....) 4.3 In search of dark matter particles. Cryogenic and non-cryogenic techniques. Objectives and results some dark-matter experiments (DAMA, XENON, DarkSide, ...) 4.4. Measurements of very high energy cosmic rays by experiments from the ground. Nature of cosmic rays; origin of the "GZK cutoff". Objectives and results of the AUGER experiment. Measurements of very high energy neutrinos. Objectives and results of the IceCube experiment. The birth of multi-messenger astronomy.
Prerequisites for admission
No special prerequisites. It is sufficient for the attending student to have mastered the concepts learned in the first years of the Corso di Laurea and to have the ability of applying them in a flexible way even outside the framework of the courses in which those concepts are taught.
Attendance: strongly recommended. Format of the classes: traditional, with the help of blackboard, handouts, slides.
To further address the topics presented in the course and to go deeper into specific aspects if so desired, the student may wish to look up: J.M. Pasachoff, A. Filippenko "The Cosmos: Astronomy in the New Millennium", 5th ed., Cambridge University Press (2019) H. Bradt "Astronomy Methods: A Physical Approach to Astronomical Observations", Cambridge University Press (2004) C.R. Kitchin "Astrophysical Techniques", Institute of Physics Publishing, 4th ed. (2003) G. Lodato "Appunti del corso di Introduzione all'Astrofisica: Buchi neri", http://cosmo.fisica.unimi.it/assets/IntroAstro/IntroAstro1819/LectureNo… A. Goobar, L. Bergstrom "Cosmology and Particle Astrophysics", Springer-Praxis Books, 2nd ed. (2004) D. Perkins "Particle Astrophysics", Oxford University Press (2003)
Assessment methods and Criteria
The exam is an oral exam focusing on the topics taught in the course. Typically, the exam takes 45 minutes and is based on three questions covering the three main parts of the Course.