  Recent measurements of the temperature fluctuations of the cosmic microwave
background (CMB) radiation from the WMAP satellite provide indication of a
non-Gaussian behavior. Although the observed feature is small, it is detectable
and analyzable. Indeed, the temperature distribution P^{CMB}(Delta T) of these
data can be quite well fitted by the anomalous probability distribution
emerging within nonextensive statistical mechanics, based on the entropy S_q =
k (1 - \int dx [P(x)]^q)/(q - 1) (where in the limit case q -> 1 we obtain the
Boltzmann-Gibbs entropy S_1 = - k \int dx P(x) ln[P(x)]). For the CMB
frequencies analysed, \nu= 40.7, 60.8, and 93.5 GHz, P^{CMB}(Delta T) is well
described by P_q(Delta T) \propto 1/[1 + (q-1) B(\nu) (Delta T)^2]^{1/(q-1)},
with q = 1.04 \pm 0.01, the strongest non-Gaussian contribution coming from the
South-East sector of the celestial sphere. Moreover, Monte Carlo simulations
exclude, at the 99% confidence level, P_1(Delta T) \propto e^{- B(\nu) (Delta
T)^2} to fit the three-year WMAP data.
