Star is considered to be formed by self gravitating collapse of the
interstellar gas in the gas (molecular) cloud which is observed by molecular
emission lines such as CO line. Molucular clouds observed in Taurus and Orion
are typical examples. The dense core in the molecular cloud is called
molecular cloud core. The molecular cloud cores in Taurus observed by C18O
isotope molecules typically have radius=0.2 pc and number density of
Hydrogen molecules=10000 particle/cc.
Temperature is almost constant at T=10 K.
Young Stellar Objects are often to be associated with the molecular cloud
core.
Let's follow the star formation from when the isotrope spherical molecular
cloud starts to collapse and increases its central density by its
self-gravity, through forming a high density molecular cloud core, to the
on set of the young star formation.
To show initial states, please place the mouse on figures.
The figure has loglismic axes and the center is enlarged.
The flow toward the center is formed by the gravitational instability,
the density at the center is increasing. At the last stage, the central
density is 1000 times larger than initial value.
Isothermal spherical Hydrodynamic equations with self-gravity.
Please refer THIS document (PDF file in Japanese)
for detailed explanation.
Ogino, S., Tomisaka, S., \& Nakamura, F. 1999, PASJ, 51, 637