cosmic microwave background

cosmic microwave background
Name	Cosmic Microwave Background
Discovered	1965
Discoverers	Arno Penzias and Robert Wilson
Wavelength	Millimetre to centimetre
Temperature	2.725 K

cosmic microwave background

Introduction

The cosmic microwave background is the nearly isotropic relic radiation filling the observable Universe, interpreted as the cooled remnant of the hot early state associated with the Big Bang and the era of recombination. Measurements of this radiation underpin the Lambda-CDM model and constrain parameters inferred by analyses from projects such as COBE, WMAP, and Planck. Interpretations tie to concepts developed by George Gamow, Ralph Alpher, Robert Herman, and later tested against datasets produced by instruments conceived at institutions like Bell Labs, Jet Propulsion Laboratory, and European Space Agency.

Discovery and observational history

The empirical detection in 1965 by Arno Penzias and Robert Wilson at Bell Labs confirmed theoretical predictions by Ralph Alpher and Robert Herman, providing decisive support for the Big Bang framework over alternatives such as the Steady State theory. Follow-up mapping by the COBE satellite team including John C. Mather and George Smoot measured the spectrum and established isotropy, leading to a Nobel Prize in Physics for Mather and Smoot. Subsequent high-resolution missions—Wilkinson Microwave Anisotropy Probe, led by scientists including David Wilkinson and teams at Princeton University and NASA, and the Planck mission operated by European Space Agency with principal investigators such as Nazzareno Mandolesi and Jean-Loup Puget—produced detailed anisotropy and polarization maps. Ground-based and balloon-borne programs from facilities like the South Pole Telescope, Atacama Cosmology Telescope, BOOMERanG, and collaborations such as BICEP2 and POLARBEAR extended angular and frequency coverage, engaging groups at Harvard University, Caltech, Stanford University, and University of Chicago.

Physical properties and spectrum

The radiation approximates a blackbody spectrum at a temperature of about 2.725 K as established by COBE-FIRAS, with spectral measurements cross-checked by instruments from NASA, European Space Agency, and laboratories at Massachusetts Institute of Technology and Caltech. The spectrum constrains energy injection from processes involving Big Bang nucleosynthesis and particle physics candidates such as hypothetical dark matter annihilation, tested against models developed at Fermilab, CERN, and Lawrence Berkeley National Laboratory. Frequency-dependent foregrounds from the Milky Way—including synchrotron emission associated with Galactic Center activity and thermal dust traced by surveys from IRAS and Herschel Space Observatory—require component separation techniques pioneered by teams at Max Planck Institute for Astrophysics and Institute of Space and Astronautical Science. Precision spectrum limits inform constraints on departures from a perfect Planck law predicted in scenarios involving inflationary universe models attributed to theorists such as Alan Guth and Andrei Linde.

Anisotropies and polarization

Small temperature anisotropies, first robustly characterized by COBE and later mapped by WMAP and Planck, reveal acoustic peak structure predicted by adiabatic perturbation theories and quantified via power spectrum analyses undertaken by collaborations at Princeton University, University of Cambridge, and University of Oxford. Polarization fields—decomposed into E-modes and B-modes—provide tests for tensor perturbations generated during cosmic inflation; experiments such as BICEP2, POLARBEAR, and SPTpol reported measurements interpreted by teams at Harvard–Smithsonian Center for Astrophysics, California Institute of Technology, and University of Minnesota. Detection claims for primordial B-modes require rigorous foreground accounting informed by surveys from Planck and radio observatories like the Very Large Array, as coordinated by groups at National Radio Astronomy Observatory and Max Planck Institute for Radio Astronomy.

Cosmological implications and models

CMB observations tightly constrain cosmological parameters—Hubble constant, baryon density, dark matter density, spatial curvature—within the Lambda-CDM model framework developed by researchers at institutions including University of Chicago and Cambridge University. Measurements influence models of structure formation studied at Institute for Advanced Study, Kavli Institute for Cosmological Physics, and Perimeter Institute for Theoretical Physics. Constraints on inflationary potentials from CMB data inform theoretical work by Paul Steinhardt, Stephen Hawking, and Andrei Linde, while alternatives such as ekpyrotic universe proposals involve contributions from Paul Steinhardt and collaborators. CMB lensing measurements by Planck, ACT, and South Pole Telescope teams trace growth of large-scale structure, complementing galaxy surveys like Sloan Digital Sky Survey and Dark Energy Survey and linking to dark energy studies at European Southern Observatory and Lawrence Livermore National Laboratory.

Measurement techniques and experiments

Techniques span satellite missions—COBE, WMAP, Planck—to ground-based arrays such as Atacama Cosmology Telescope, South Pole Telescope, and the Very Large Array for ancillary foreground studies. Balloon experiments including BOOMERanG and MAXIMA provided intermediate-scale maps, while interferometric approaches by teams at Caltech and MIT advanced calibration and systematics control. Detector technologies—transition-edge sensors, bolometers, and microwave radiometers—were developed at laboratories such as Jet Propulsion Laboratory, NASA Goddard Space Flight Center, and National Institute of Standards and Technology and deployed by collaborations including BICEP2, POLARBEAR, SPIDER, and CLASS. Data analysis pipelines and likelihood codes originated in groups at Princeton University, University of Chicago, and Max Planck Institute for Astrophysics, integrating map-making, component separation, and parameter estimation with frameworks used by Euclid preparatory teams and Large Synoptic Survey Telescope planners.

Category:Cosmology