NATS 1745 Lecture Notes - Lecture 10: Henry Draper Catalogue, Planetary Nebula, Harvard College Observatory
17 Jul 2017
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Document Summary
All scientists were trying to detect parallax on stars that were bright because they thought that meant they were the closest. Halley compared ancient star catalogues with current star positions and found moving stars, suggested that stars have unique motion across the sky. What is the definition of a parsec? (note: the specific values in km aren"t necessary here). Light year (ly): the distance light travels in 1 year (e. g. a star 10 light years away is seen as it appeared 10 years ago) Parsec (pc): parsec is the inverse of parallax measured in arc seconds. Waves of oscillating electric and magnetic fields. Amplitude: determines the intensity of light source. Wavelength: determines the colour of a light source. Sun"s spectrum contains absorption lines and continuum: describe (briefly) how the chemical composition of a star can be determined. Light is made up of many different colours, or wavelengths.
