ASTRON 10 Lecture 9: The Spectrum

• School: Berkeley
• Department: Astronomy
• Course: ASTRON 10
• Professor: Sperling Norman

Document Summary

Studying a star is like looking at a rainbow: Each color that makes up light corresponds to a certain wavelength. Electromagnetic waves are self-propagating and oscillating (getting larger and smaller) electric and magnetic fields. Hotter stars give off more energy in shorter wavelengths. Continuous spectrum - a spectrum that changes smoothly in brightness from one color to the next. A very dense gas or solid gives off continuous spectrum. Blackbody - a simple opaque object that absorbs all radiation that is incident upon it (no radiation is reflected or transmitted) Blackbody radiation/thermal radiation - the result that the shape of the emitted continuous spectrum depends on the object"s surface temperature and not on its chemical composition. Spectra of hotter blackbodies peak (have their highest brightness) at shorter wavelengths than spectra of colder blackbodies. Hotter blackbodies emit more energy per second than colder ones. Planets are cooler than stars, so they give off most of their radiation through infrared (thermal)