NASA Logo, National Aeronautics and Space Administration

National Aeronautics and Space Administration

Goddard Space Flight Center

Astrophysics Science Division | Sciences and Exploration

This website is kept for archival purposes only and is no longer updated.

CMB Measured Intensity vs Frequency

The plot below shows a set of precise measurements of the intensity of the cosmic microwave background (colored points) compared to a perfect blackbody curve (thin black line). Colors indicate the measurement techniques. The data are in excellent agreement with a blackbody curve over nearly 4 decades in frequency and more than 5 orders of magnitude in intensity.
CMB intensity vs frequency
The most precise measurements of the CMB spectrum at the millimeter wavelengths near its peak were made by the Far Infrared Asbolute Spectrophotometer (FIRAS) instrument aboard the Cosmic Background Explorer (COBE) satellite. FIRAS determined the CMB temperature to be 2.725 +/- 0.001 K, with deviations from a perfect blackbody limited to less than 50 parts per million in intensity. ARCADE measures the CMB spectrum at centimeter wavelengths (a decade below FIRAS) to search for new signals that would be undetectably small at the shorter wavelenghts measured by FIRAS.