This website is kept for archival purposes only and is no longer updated.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