The goal of this course is to provide the students with a general overview of stellar physics. Starting from the fundamental properties of stars as inferred from observation (photometry, spectroscopy, parallax, mass measurements in binary systems), the features of physical stellar models are introduced. These include the equations of stellar equilibrium, energy production, stellar evolution. Along the path, some of the fundamental physical quantities and concepts of astrophysics are introduced, which will be a basis for the course Astronomy II and for other courses in the astrophysics curriculum.
Expected learning outcomes
Students at the end of the course are expected to reach the following capabilities: 1. to correctly use basic quantities and concepts, such as luminosity and magnitude (relative and absolute), surface brightness, flux density, effective temperature, luminosity radius, etc. 2. to describe the main properties of a stellar spectrum, continuous radiation and absorption lines 3. to calculate relative velocities of astrophysical sources from Doppler effect measurements, and to evaluate the effects of temperature and pressure from the shape of absorption line profiles 4. to be able to discuss the main properties of the Sun, its structure, cycle, magnetic activity, the characteristics of the photosphere, chromosphere, corona 5. to gain familiarity with the mechanisms of nuclear energy production in stars, including the information of solar interior from helioseismology and neutrino physics 6. to gain familiarity with the equations of stellar equilibrium, af the mechanisms of radiative and convective energy transfer in the interior of stars 7. to be able to discuss stellar evolution for stars of different mass ranges, including their final stages 8. to be able to discuss the properties of degenerate gas, the nature of white dwarfs and neutron stars, the conditions for the formation of a stellar black hole 9. to be able to calculate astronomical distances from observations of stellar properties, including measurements of trigonometric parallax, spectroscopic parallax, measurement of Cepheid variables, Supernovae Type Ia
Lesson period: First semester
(In case of multiple editions, please check the period, as it may vary)
1) Fundamental properties of stars - Continuum radiation from stars. Brightness. Electromagnetic spectrum. Planck's law. Color indexes. Distance and absolute magnitude. Spectral lines and spectral classes. Origin of spectral lines. Hertzsprung-Russell diagram. Main sequence. Doppler effect. Binaries with circular orbits. Masses and sizes of stars. The Sun as a typical star. Internal structure of the Sun. Photosphere, chromosphere, corona. Solar activity. 2) Stellar structure - Source of stellar energy. Nuclear astrophysics: nucleosynthesis in equilibrium conditions. Proton-proton chain. CNO cycle. The Sun as a main sequence star. 3) Stellar evolution - Evolution of stars of solar mass. Beyond the main sequence. Giant stars. Cepheid variables. Planetary nebulae. The final stages of massive stars. Supernovae and SNe remnants. 4) Telescopes and astronomical instrumentation - Optical telescopes. Effective area, angular resolution. Seeing. Refractive and reflective telescopes. Ground based observatories. Hiubble space telescope. Infrared and sub-mm astronomy. Observations in the microwaves. Radioastronomy. Ground based observations and space missions. Observations in the UV. X-ray astronomy. Gamma-ray astronomy. Space telescopes for high energy observations. 5) The Milky Way - Stellar clusters. Globular and open clusters. Dynamics of clusters. HR diagrm for stellar clusters. Stellar populations. Introduction to the interstellar medium. 6) Extragalactic astronomy and Cosmology - Normal galaxies, classification. Star formation in galaxies. Spiral structure. Dark matter in galaxies. 7) Solar System and extrasolar planets - The Earth-Moon system- Origin and structure of planet Earth. Plate tectonics. Basics of Earth's atmosphere physics. Magnetosphere. Tides. The Moon, origin and structure. Solar system planets. Terrestrial and giant planets: surface, atmosphere, internal structure. Rings and satellites. Minor bodies. Origin of the solar system. Astrobiology. Chemistry of the primordial Earth. Stability of terrestrial environment and biological evolution. Potential for life elsewhere in the solar system and beyond. These subjects are taken from Unit 1 and 2 of the course of Astronomy for the Degree in Physics.
Prerequisites for admission
Familiarity with the notions of mathematics and physics as offered by the Bachelor Degree of Natural Sciences. Interest in multidisciplinary contents, training in scientific discussion.
Lectures are carried out using also multimedia material. Exemplifications of the contents, typically taken from contemporary scientific literature, are offered during lectures. The students are regularly solicited to take part in the discussion and to interact during lectures. We also propose an optional activity of field astronomical observation at the telescopes at INAF Brera-Merate.
A few reference textbooks are suggested (Marc L. Kutner, "Astronomy: a Physical Perspective", Cambridge Univesity Press, 2003; D. Maoz, "Astrophysics in a nutshell", 2008, Princeton University Press). The lectures utilize slides, which are regularly made available to the students on the course web page, and multimedia material. For some topics, review papers available online are indicated to the students.
Assessment methods and Criteria
The exam consists of a discussion on the topics covered by the course. Starting from a plot, an example or a simple exercise the student will be required to discuss theoretical contents. The final evaluation will take into account the level of critical understanding reached by the student.