Cosmic Microwave Background

The Cosmic Microwave Background, or CMB, is a faint glow in microwave radiation that is almost perfectly uniform across the sky.  This thermal radiation was emitted about 380,000 years after the Big Bang, as the universe became transparent for the first time. 

The CMB peaks at a wavelength of about 2 mm with a nearly perfect blackbody spectrum corresponding to a temperature of 2.73 K. Although the CMB is extremely uniform, there are slight polarizations and variations in temperature throughout.  These very faint features offer important glimpses into the physics of the early universe.

By using a key signal from the CMB, KIPAC researchers hope to learn whether cosmologial inflation happened – and if it did, then how? If the universe experienced cosmological inflation – a brief moment of rapid, exponential expansion just after the Big Bang – then the process of inflation may also have created gravitational waves. These waves would have left an imprint on the CMB in the form of faint polarizations known as B-modes.  These patterns could not have been created by the same properties that gave rise to the warm and cold spots within the CMB.  Instead, B-modes are believed to be a clean signature of the conditions that prevailed in the early universe, known as new physics.

KIPAC researchers are actively pursuing this goal through several experiments. The CHIP project is developing advanced coherent detectors that can be constructed and deployed in large arrays for future telescopes. BICEP2 and the Keck Array, ground-based telescopes now taking data at the South Pole and targeted at a detection of B-modes, are part of this initiative.  POLAR-1 and the POLAR Array are planned successor experiments with larger numbers of detectors capable of finer resolution.

KIPAC researchers are also taking part in the Planck project, a satellite observatory designed to map the CMB across the whole sky.  By taking full-sky CMB measurements with improved angular resolution and sensitivity, Planck will provide a rich set of data with wide applications to cosmology and astrophysics.

Click the images below to see a larger version

All-sky temperature map of the CMB from the WMAP satellite. This image was created using seven years of data and shows temperature variation on a scale of ±200 mK. Credit: NASA / WMAP Science Team. Full resolution image: