1 / 14

Exploring Stellar Atmospheres: Understanding the Secrets of Stars

Delve into the intriguing world of stellar atmospheres, from defining their role and structure to deciphering spectral lines. Learn about the impact of radiation transfer and the interaction between photons and atmospheric elements. This course covers essential topics in stellar atmospheres and radiation transfer essential for understanding the cosmos.

bwilder
Download Presentation

Exploring Stellar Atmospheres: Understanding the Secrets of Stars

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Stellar Physics:Stellar Atmospheres (13)Stellar Structure & Interiors (11) Kenneth Wood, Room 316 kw25@st-andrews.ac.uk http://www-star.st-and.ac.uk/~kw25

  2. Course Texts • Radiative Transfer in Stellar Atmospheres (Rutten) On web and in library • Stellar Structure & Evolution (Prialnik) • Stellar Atmospheres (Mihalas) • Observation & Analysis of Stellar Photospheres (Gray)

  3. Lectures, Tutorials, & Exam • 27 scheduled lectures • Coursework: 24 lectures (including today) • 2 Tutorial sheets. Do you want more? • Lecture notes on web • Degree Exam in January • 3 long questions: answer 2 • 5 short questions: answer all

  4. What is a Stellar Atmosphere? • Transition from dense stellar interior to interstellar medium. • Region that produces the stellar spectrum. The physical depths in the atmosphere where the spectral features form depend on the atmospheric conditions: temperature, density, level populations, optical depth… • We see radiation from the “optical depth one surface” • Goal: From analysis of spectral lines and continua, determine physical conditions, chemical abundances, mass loss rates…

  5. Balmer Lines & Balmer Jump a Lyra • H-opacity ~ l3 • Jump at Balmer “series limit” • Size of jump: estimate temperature & pressure

  6. Model Atmosphere • Expect “saw tooth” due to H opacity • Line blanketing…

  7. Line Blanketing • UV opacity from metals • Blocks flux: blanketing • Fe, Al,… • Temperature diagnostic

  8. P-Cygni Line Profiles • Expanding atmosphere or stellar wind • Wind speed from blue edge • UV space astronomy (1960s): wind theories

  9. Simplifications, but not simple… • Plane parallel • Time independent • Hydrostatic equilibrium • No magnetic fields

  10. The Sun

  11. The Solar Corona

  12. What happens physically? • Photons emitted, travel some distance, interact with atmospheric material • Scattered, absorbed, re-emitted • Photon interactions heat atmosphere, change level populations, ionization balance • Hydrostatic equilibrium: density structure related to temperature structure • Atmospheric structure depends on radiation field and vice versa • Atmosphere model requires detailed study of radiation transfer: bulk of this course

  13. Stellar Atmospheres & Radiation Transfer: 13 Lectures • Radiation transfer recap: equations, definitions (2) • Opacity sources & LTE (2) • Formal, approximate & analytic solutions (3) • Model atmospheres (1) • Spectral lines (2) • Circumstellar material: Monte Carlo (3)

  14. 2. Radiation Field Basics I • Rutten: 2.1 • Basic definitions of intensity, flux • Energy density, radiation pressure

More Related