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Universe_CompositionFate_forclass2

Universe_CompositionFate_forclass2 - CMBR and cosmology T a...

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CMBR and cosmology Take a trip in time/out in space to put "earliest light" in perspective movie
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Cosmic Background Explorer (COBE) 3 instruments: FIRAS, DMR and DIRBE Cryogens ran out on 9/ 21/ 90 ending observations by FIRAS and longer wavelengths of DIRBE DMR and the shorter wavelengths of DIRBE operated until 11/23/93
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COBE data/DIRBE Diffuse InfraRed Background Experiment IR background is produced by dust warmed by all the stars that have existed since the beginning of time Limit to energy produced by all stars in the Universe
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COBE data/FIRAS Far InfraRed Absolute Spectrophotometer
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COBE data/FIRAS FIRAS results show that 99.994% of the radiant energy of the Universe was released within the first year after the Big Bang Data match the Big Bang predictions so exactly that the error bars are within the curve itself Residuals from a 2.726 (+/- 0.004) degree Kelvin blackbody
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COBE data/FIRAS The CMBR is described by the most perfect blackbody spectrum ever measured Blackbody spectra are produced when material is thick and dense, so that photons must scatter many times before they escape The photons must therefore have been emitted from dark, thick matter at a much earlier time The CMBR energy was emitted when the Universe was 10 6 times smaller and hotter than it is now. Photons continued to scatter until the Universe was 10 -3 its present size
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Ω (total) = Ω M where Ω M = matter density (including regular and dark matter) Ω tot = density/critical density If Ω tot = 1,Universe is flat, expansion coasts to a halt as Universe is critically balanced. Old view: Density of the Universe
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COBE data/DMR Differential Microwave Radiometer Dipole due to movement of Solar System warm cool
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COBE data/DMR Dipole removed to show “wrinkles”
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COBE data/DMR Fluctuations in CMB seen by DMR are at the level of one part in 100,000 Blue spots mean greater density Red spots mean lesser density (in the early Universe)
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Some Review Questions What does the term ‘dark matter’ refer to? Where do we think it is located in the universe? How was dark matter detected? Why do the rotation curves of spiral galaxies suggest the existence of dark matter? Why does dark matter need to be ‘cold’ rather than ‘hot’ in order to explain the structure that we see in the universe? What is the virial theorem? What do we mean by ‘non-baryonic’ dark matter candidates, and can you name some? What has been suggested as potential baryonic dark matter candidates?
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CMBR Fluctuations COBE measures the angular fluctuations on large scales, down to about L=16 Astronomer’s divide the sky into angular degrees.
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