Tags: Star.
Young stellar object (YSO) denotes a star in its early stage of evolution.This class consists of two groups of objects: protostars and pre–main sequence stars. Sometimes they are divided by mass – massive YSO (MYSO) intermediate mass YSO and brown dwarfs.YSO are usually classified using criteria based on the slope of their SED introduced by Lada C.J. in 1987.