Exam 2 Outline

O method compare observed spectrum with laboratory

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find its thermal, chemical and dynamical properties. o Method: compare observed spectrum with laboratory spectra of known gasses under known conditions. o Each possible transition is unique to that element Light has energy NOT mass Ultraviolet light can burn skin (sunlight) Infrared is HEAT; therefore, cannot burn skin but can be FELT. Most of the universe is gas Light is an electromagnetic wave but can come in individual pieces called photons . The shorter the wavelength, the HIGHER the frequency and energy! In order of DECREASING WAVELENGTH(increasing frequency and energy): Radio waves, microwaves, infrared, visible light, ultraviolet, xrays, gamma rays. Isotopes of a particular chemical element all have the same number of protons but different numbers of neutrons. Molecules are made from two or more atoms. There are three basic types of spectra: continuous spectrum (which looks like a rainbow); absorption line spectrum (specific colors are missing from the rainbow); and emission line spectrum (we see light only with specific colors against a black background)
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Objects such as planets and stars produce thermal radiation spectra (most common type of continuous spectra). We can determine temperature because hotter objects emit more total radiation per unit area and emit photons with a higher average energy. The Doppler Effect tells us how fast an object is moving toward (blue shift) or away (redshift) from us. The “Discovery” of Dark Matter Gravity and Motion o How do things move because of gravity? Newton’s “Classical Mechanics” Einstein’s spacetime of General Relativity Both depend on the amount of mass (and as Einstein showed, Energy=mass) Options for galactic dynamics o Rigid (solid-body) rotation o Orbits The larger the spatial scale the more DARK MATTER dominates!
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