3.Gas Clouds and Star Formation Many gas clouds are observed in the region of space near the Milky Way galaxy,and it is assumed that such clouds exist throughout the universe.
a Some of these clouds are diffuse clouds of hydrogen with temperatures of 50 K.den sities of 5 10 particles/m and total masses in the range of 1-100 solar masses (Mo.If we assume such clouds are entirely composed of HIie.atomic hydrogen with =1.will such a cloud collapse to form a star? b Other gas clouds,called Giant Molecular Clouds,are also observed.These contain material in addition to hydrogen (mostly helium,but with more complex molecules as well.These clouds are hugewith total masses of up to 10Mo,and contain small dense regions within them. These denser regions containing between 10-1000 Mo of materialhave temperatures of 150 K and densities of 1013-10particles/m.If it is assumed that such clouds are 75% H and25%Hewith =1.23ean these dense regions collapse to form a star? c Assuming that at least one of the two scenerios described above will result in the col- lapse of the gas cloud,what is the miniumum initial size of the collapsing cloud
4.Collapsing Gas Clouds In the calculation of the free-fall time we assumed that there were no collisions between the particles in the gas cloud ie. no intermal pressure and that the collapse was an isothermal process.
a Assuming that the material in a gas cloud behaves as an ideal gas. i What is the initial pressure in the collapsing gas cloud described in the above scenerios? ii. Is the assumption that there is no pressure reasonable? bAssuming that the temperature remains constant isothermal collapse). i. What will the radius of the collapsing object be when the pressure has increased to some significant value1 atmosphere?I atm 10Pa ii.How docs this size compare to the size of the sunRg=6.9610m iii.What is this expressed in astronomical units?1A.U.=1.49610m c When estimating the minimum Jeans'mass during the collapse and fragmentation pro cess we used a temperature of 1000 K as the point at which the collapse process would move from being an isothermal (constant temperature)to an adiabatic (constant energy) process.. i. What are the processes by which electromagnetic radiation is absorbed by matter? ii.What is functionally different aboout the constitutents of the gas cloud at T=I00 KvsT=1000K2 ii. How would this affect the absorption of radiation iv. Why did we choose the value of 1000 K to approximate when the collapse moves from being an isothermal to an adiabatic process?