Although a blackbody does not really exist, we will consider the planets and stars (including the earth and the sun) as blackbodies. ... According to the above definition, a blackbody will emit radiation in all parts of the EM spectrum, but by intuition, we know that one will not radiate in all wavelengths equally.

Is perfect black possible?

A perfect blackbody is one that absorbs all incoming light and does not reflect any. At room temperature, such an object would appear to be perfectly black (hence the term blackbody). ... Fortunately, it is possible to construct a nearly-perfect blackbody.

Why it is not possible to achieve a perfect blackbody?

but we cant measure this perfect spectrum because all objects will reflect some of the radiation distorting the reading for the wavelength of radiation reflected. It is not just reflection, it is also quantum mechanical transitions for bodies consisting of different atomic and molecular structures.