The NGC 1333 IRAS 4A protobinary was observed in the ammonia ( 2 , 2 ) and ( 3 , 3 ) lines with an angular resolution of 0.3 arcsec .
The ammonia emission source of IRAS 4A2 is elongated in the direction perpendicular to the bipolar jet and has a size of 0.55 arcsec or 130 AU .
This emission structure was interpreted as a circumstellar disk around the IRAS 4A2 protostar , and the rotation kinematics of the disk was investigated by making a position-velocity diagram along the major axis .
Assuming a Keplerian rotation , the disk has a rotation velocity of 1.8 km s ^ { -1 } at a radius of 20 AU , which implies a central object of about 0.08 solar masses .
The collapse age of the protostar is about 50,000 yr .
The mass , accretion rate , and age are consistent with what are expected from the standard theory of low-mass star formation .
If IRAS 4A2 grows at this rate , it may become a star similar to the Sun .