Wikipedia disagrees.
"A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. (It does not only absorb radiation, but can also emit radiation. The name "black body" is given because it absorbs radiation in all frequencies, not because it only absorbs.)"
It really doesn't.
This might help. http://astronomy.swin.edu.au/cosmos/B/Blackbody+Radiation
Note the line 'As the temperature of the blackbody increases, the peak wavelength decreases'
Just because some things can be approximated for varying degrees of usefullness as absorbing and emitting equally well on all frequencies (which the earth is really bad at anyway), does not mean they are stable in temperature.