ASTROPHYSICAL MEASUREMENTS
Academic year and teacher
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- Versione italiana
- Academic year
- 2016/2017
- Teacher
- CRISTIANO GUIDORZI
- Credits
- 6
- Didactic period
- Secondo Semestre
- SSD
- FIS/05
Training objectives
- An ample review of how astrophysical quantities get measured is presented through the course along with the fundamental aspects of physics upon which the measures are obtained. Examples of quantities are stellar masses, different distance scales across the Universe (the so-called cosmic ladder), gas temperature in various astrophysical environments, the most relevant radiative mechanisms in astrophysics and the basic physics these processes are based on. Consequently, along the astrophysical examples and contexts, the theory behind it is presented in parallel, discussing elements of fundamental physics, classical electromagnetism, special relativity and some basics of quantum mechanics. The ultimate goal is supplying the student with the basic knowledge that will allow him to pursue a more specific project concerning several among the hottest and most debated topics of modern and cutting-edge astrophysics and cosmology.
Prerequisites
- Fundamental physics (kinematics, dynamics of point mass particles and of systems of particles), fluidodynamics, waves, thermodynamics. Electromagnetism. Infinitesimal calculus. Special relativity. Basic elements of quantum mechanics.
Course programme
- Atmospheric refraction. Precession. Nutation. Parallax. Geocentric parallax. Stellar parallaxes. Definition of parsec. Gregory's method to estimate the distance to Sirius. Measure of the speed of light. Daily and annual aberration of light. Relativistic aberration. Classification of binary systems. Equations of motion and solutions for a binary system. Conics and Kepler laws. Orbital parameters. Relative and barycentric orbits. Escape velocity. Virial theorem. Visual binaries. Spectroscopic binaries. Mass function. Eclipse binaries. Overview of exoplanets and discovery techniques. Roche model. Cosmic rulers: Cepheids. Elements of stellar evolution. Type-Ia supernovae. The Phillips relation and accelerated expansion of the Universe. Tully-Fisher relation. Cosmic ladder. X-ray binaries and mass function. Mass accretion. Eddington limit. Accretion in the context of super massive black holes (SMBH) and active galactic nuclei (AGN). Polarisation of light and its importance in astrophysics. Classical electrodynamics: Poynting theorem. Lienard-Wiechert potentials. Larmor formula. Dipole approximation. Thomson scattering. Bremsstrahlung. Thermal bremsstrahlung and astrophysical examples. Synchrotron radiation for a single charged particle and for a power-law distributed population. Astrophysical examples of synchrotron radiation. Compton and inverse Compton scattering. Propagation of electromagnetic waves through astrophysical plasmas in the presence/absence of a magnetic field. Dispersion measure. Faraday rotation. A new and yet mysterious problem in the transient astrophysics domain: fast radio bursts (FRB).
Didactic methods
- The lectures are delivered through slides that the teacher makes available on the web sooner after they have been presented and discussed. During classes the teacher very often intersperses slides with calculations of the relevant quantities are estimated by means of specific examples and exercises. This way, the student becomes very familiar with the kind of exam and the sort of questions he/she will be expected to address in the oral exam, as well as with the evaluation criteria adopted by the teacher.
Learning assessment procedures
- During classes the teacher occasionally assigns exercises along with the numerical values of the solutions to motivate the students to practice and test the knowledge they are expected to acquire on the topics presented by the teacher. A detailed step-by-step solution is available on request to the students in the following weeks. The final exam consists of a unique oral session with a typical duration of 45 to 60 minutes, during which the student is asked both general questions about theory and more specific problems. These, in particular, will test the student's capability of properly addressing the problems. To this aim, the student will have to know the values of the fundamental constants and how to use them to estimate the requested astrophysical quantities.
Reference texts
- The textbook as well as the slides written and used by the teacher during classes are made available on the web. Follows a detailed list of references where the student can go deeper.
1) H. Karttunen et al., "Fundamental Astronomy", Springer
2) H. Bradt, "Astrophysics Processes", Cambridge
3) G.B. Rybicki, A.P. Lightman, "Radiative Processes in Astrophysics", Wiley
4) M. Longair, "The Cosmic Century", Cambridge
5) R. de Grijs, "An Introduction to Distance Measurement in Astronomy", Wiley
6) M. Perryman, "The Exoplanet Handbook", Cambridge.
7) M. Vietri, "Astrofisica delle Alte Energie", Bollati Boringhieri.
8) G. Ghisellini, "Radiative Processes in High Energy Astrophysics", Springer
9) J. Frank, A. King, D. Raine, "Accretion Power in Astrophysics", Cambridge
10) R.W. Hilditch, "An Introduction to Close Binary Stars", Cambridge
11) H.G. Lewin, M. van der Klis, "Compact Stellar X-ray Sources", Cambridge
12) J.E. Truemper, G. Hasinger, "The Universe in X-Rays", Springer
13) C. Grupen, "Astroparticle Physics", Springer
14) Burke, B.F., Graham-Smith, F.: An Introduction to Radio Astronomy. Third Edition. Cambridge University Press (2010).
15) Marr, J.M., Snell, R.L., Kurtz, S.E.: Fundamentals of Radio Astronomy. Observational Methods. CRC Press, Taylor & Francis Group (2015).
