Processes of evolution in astrophysics

This thesis consists of two parts; part I deals with the origin of the terrestrial planets while part II is concerned with evolution of larger objects, stellar clusters. PART I. Chapter I: A general outline of the problems involved in the formation of planets and a brief indication of our proposed solution is given. Chapter 2: The resistance offered by a gas to an object moving through it with different speeds is calculated and a comparison between the expressions found is given. The equation of growth for an object accreting material is also found. Chapter 3: The time taken by an object to fall to the centre of a gas cloud under the action of the gravitational attraction of the cloud and the resistance of the gas is found. The resistance and growth laws found in Chapter 2 are used. Chapter 4: The possibility of forming very large grains, or clumps, by accretion and the probability that theseescape from the cloud on collision is investigated. Chapter 5: An estimate for the dispersal time of a condensation violating the Roche limit is given. Chapter 6: This gives a brief outline of the proposed theory together with tbs conclusions about the whole part. PART II. Chapter 1:This gives an explanation to some of the terms used in connection with stellar evolution and indicates some of the problems involved. Chapter 2: The problem of stars contracting; onto the main sequence is considered, showing the importance of the initial conditions chosen. Chapter 3: A discussion about the blue stragglers found in some clusters is given and an investigation into the possibility that this phenomena is caused by continuous creation of stars in the cluster is carried out.