PHYSICS GOVERNING STAR FORMATION 1 PHYSICS GOVERNING STAR FORMATION Name: Institution: Date:
PHYSICS GOVERNING STAR FORMATION 2 Introduction One of the processes that are thought to play a role in star formation is mass accretion. It is assumed to be the other most interesting possibility. However, there are some critics who argue that there would be an adverse process in the accretion process due to the high radiation pressure brought by massive stars. However, if radiation momentum is not larger than the accretion flow momentum, it is possible for the process of accretion to occur. There are several models that confirm this possibility. Findings One model postulates that, a constant accretion rate M acer of approximately 10 -5 M ʘ yr -1- would take a period of 10 7 yr to form a star of 100M ʘ , while another observation suggests the formation age to be ~ 10 5 yr. It is possible to have high accretion rates in the event that contracting clumps in the interstellar cloud has a high density. This condition usually produces locally high-density conditions that make it possible for massive stars to form. Gibbs and Horne (2013) states that stars are formed in molecular clouds. These clouds are composed of dust-coated ice and gas. Previously, water has been detected outside the Solar System in form of ice and gas coated onto tiny dust grains near the sites where star formation occurs. In the initial moments of formation, these stars are surrounded by a disk. Planetary systems are formed from these disks. However, there are some processes of chemical and physical dust grain evolution which have not been understood. For massive stars to form, there has to be a lot of of dense gas. Self-gravity is likely to dominate massive clouds (exceeding 10 3 M ʘ , and a density of ρ≥ 10 19 g cm − 3 . Such clouds show
PHYSICS GOVERNING STAR FORMATION 3 internal supersonic motions (Maeder 2012). This situation leads to gravi-turbulent fragmentation characterised by shock waves and eventually making the density structure highly inhomogeneous with clumps and sub-clumps leading to the formation of stars. The greatest activity occurs at the cluster center forming the most massive stars.
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- Winter '16
- Professor Obura Oluoch