  We present an analytical study of a large sample of ~109 young stellar
objects in the X-ray. Our objects were detected in X-ray independent of age.
Unexpectedly, the X-ray energy is somewhat correlated with the ages. It
decreases with time and with column density, while it should increase. We
conclude that the youngest protostars, Class 0/I, emit X-rays in the 1-8 keV
band. The deeply embedded sources with the strongest accretion activity are
detected in the hard-band (> 2keV) only. Due to extinction, their soft X-rays
are not detected. To explain the decline in energy, we suggest that within a
timescale of few Myrs the corona cools down via the accretion material.
