Ast 201 Lecture 6 26th January 2012.docx
DepartmentAstronomy & Astrophysics
Ast 201 Lecture 6 26th January 2012
How light interacts with matter
- Spectroscopy: the studying of the spectrum of light. It works by take light and splitting.
- Farunhofer: detected lines in the spectrum of the sun.
- When reading a spectrum, you must read it from left to right..
- The sun is made of hydrogen*
Atoms* (check slides) + (tutorial notes)
-Low-density gases: like a nebula or an atmosphere of a planet. Atoms just sort of float
around emitting and absorbing light at the same time. (independently of the others) we call this
an emission spectra.
- The positions of the spectral lines predict the chemical composition of the object.
- Dense Objects: ( gas,liquid, or solid) Dense objects emit some light at all wave length.
We cal this a continuous spectrum.
- Most emit very much like the blackbody spectrum.
- as it gets hotter, it emits more light at shorter wavelengths. And the more light over all.
- Low density gas in front of a blackbody: