wavelength of same line emitted by stationary source

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Unformatted text preview: "/c Where !’ = wavelength of spectral line emitted by moving source wavelength ! = wavelength of same line emitted by stationary source c = speed of light " = recessional velocity Hubble constant v = Hd H = Hubble constant d = distance • Provides a limit to the age of the universe • Time required to separate two objects is… t = d/v = 1/H • Properly calibrated, estimate comes out to be <2 x 1010 years • Agrees broadly with estimates based on stellar evolution • Current estimate: 13.7 billion years Current 13.7 Cosmic microwave radiation ! Discovered by accident in 1965 by Penzias and Wilson Discovered • Won Nobel prize in 1978 for discovery • Universe is permeated by microwave radiation at a blackbody temperature of ~2.7 K • Remnant from when universe became transparent … wavelengths are stretched out by cosmic expansion since then • Max Planck equation for blackbody radiation !max = 0.29/T ! Radiation varies slightly in temperature throughout the universe • Due to quantum fluctuations in the vacuum energy, occurring in the first fraction of a second • Inflation fixed these fluctuations in place on a cosmic scale COBE data ! COsmic Background Explorer • • • Microwave observatory launched in 1989 Measured the cosmic background throughout the sky Using these data, quantum calculations could more accurately date the origin of the universe • 13.7 billion years (±0.1 billion years) NASA Wilkinson Microwave Anisotropy Probe (WMAP) ! “Baby picture” of the Universe • Records a high-resolution image of light from 379,000 years after the Big Bang NASA NASA Hubble Deep Field ! ! ! Long exposure image of a section of sky containing no stars (at least 2º of arc away from any star of magnitude 2 or greater) Field width is very small, equivalent to a dime held 75’ away (analogy from NASA press briefing) Image contains at least 1,500 galaxies NASA's Spitzer Space Telescope • Observations of light from the first stars in the Universe Stellar Evolution ! Stars form as a result of gravitational collapse of gas clouds in space • During collapse and contraction, core temperature and pressure increases • Eventually, a critical density is reached where atoms in the core of the cloud reach pressures and temperatures that allow fusion • Stellar fusion converts (primarily) Hydrogen into Helium, emitting energ...
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This document was uploaded on 04/05/2014.

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