Problem by Hugo Alberto Luyo Sánchez
30 Nov 1999 00:00 WIB
In the modern ideas of cosmology stars 
arise from the dust and gas nebulae. Let 
consider that the star was formed if the cloud 
begins to occur a thermonuclear reaction. 
Suppose that the cloud is formed by atoms 
hydrogen, whose diameter $3\times 10^{16}$ m  and $2 \times 10^{30}$ kg mass, 
distributed evenly over the volume of the cloud 
begins to compress under the gravitational action. 
Let us consider the formation process 
star is neglected collisions between particles.

1) Show that in the compression process of the mass distributionwithin the cloud remains homogeneous.

2) Estimate for radio tag thermonuclear reactions begin.
Consider the nuclear reaction begins when the temperature reaches the value of $1,107$ K. energy losses by radiation in the compression process are neglected.

3)Estimate the time compression of the cloud to the star formation.
Consider that in the compression process can be neglected gaspressure. The gravitational constant $G  7.10^{ -11}$ $ (N • m^{2}) / kg^{2}$.