Planck microwave background polarization map
Credit: ESA and the Planck Collaboration

A New Slant on the First Stars

The cosmic microwave background is the remnant light generated at the birth of the Universe. It dates from the time when the Universe became "transparent", a time when the Universe cooled enough that electrons could recombine with protons and helium nuclei to form neutral atoms. This occurred roughly 380,000 years after the Big Bang. The cosmic radiation at this time no longer collided frequently with unbound electrons, and began to stream to the farthest reaches of the Universe. On its cosmic journey, the wavelength of this radiation stretched with the expansion of the Universe, until, after its 13.4-billion year journey, we observe it here on earth as long-wavelength microwave radiation. This radiation has been studied in increasing detail from space by the COBE, WMAP and Planck satellite observatories. The Planck satellite has provided us with the most precise measurements of the cosmic microwave background, revealing important new details of the Universe at the earliest times. The image above is an all-sky map of the cosmic microwave background obtained by Planck. As the Planck map shows, there are some slight variations in the color of this radiation: in the bluer regions, the wavelength of cosmic background radiation is a little shorter than it is in the redder regions. This reveals the extremely slight temperature decrease between the blue and red regions. If you look closely, you can see that the map is textured. This texture represents the local polarization of the cosmic background radiation, which is a measure of the dominant direction in which the wave of radiation oscillates. This net polarization is imprinted on the cosmic background radiation by the distribution of matter at the time when the radiation began its cosmic journey. Careful study of this polarization signal provides important new clues about the evolution of the early Universe, and indicates, for example, that era of formation of the first stars was a few hundred million years later than previously believed. Because of the advances provided by the Planck spacecraft, the ESA Planck team has been awarded the 2018 Gruber Cosmology Prize.
Published: May 21, 2018

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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 28-May-2018 16:29:11 EDT