lOW MASS STARS
Molecular Clouds
Molecular clouds are cold, dense clouds of dust. If the cloud's mass is great enough, the inward pull of gravity overcomes outward forces like magnetic fields and thermal pressure. When a catalyst sparks nearby the molecular cloud, it causes motions in the cloud. Motions in the cloud cause it's density to clump up, fragmenting the cloud and allowing for the formation of multiple stars. ................................................................ Protostar Some hallmarks of a protostar include protostellar discs, wind, and jets due to angular momentum. The rotation of the disk prevents gas from falling directly onto a protostar. The protostar officially becomes a star when self-sustainable nuclear fusion in it's core is achieved at 10 million K. This stage lasts approximately 30 million years. ............................................................................. Yellow Main Sequence Star Fusion occurs in the star's core. Four hydrogen nuclei fuse into a single helium nucleus, releasing energy. This process is done by the proton-proton chain. Gravitational equilibrium, a balance between the outward push of thermal pressure and the inward pull of gravity, maintains stability in the star. This stage lasts approximately 10 billion years. .............................................................................. Red Giant The red giant results from the halting of hydrogen core fusion within the core and the ignition of hydrogen fusion in the outer shell. The increased pressure within the shell overcomes gravity and the star expands into a red giant. .............................................................................. Helium Core Fusion Star As Hydrogen fusion in the shell comes to an end, the sun shrinks again; which increases core temperature. When the core temperature become hot enough, helium fusion begins. ............................................................................. Double shell-fusion Red Giant With the core of the star becoming more carbon (due to helium fusion), Helium fusion begins in the outer shell of the star. Coupled with the dwindling fusion rate of hydrogen in the outermost layer, the star once agains overcomes gravity and becomes a double shell-fusion red giant star. ........................................................................... Planetary Nebula The planetary nebula is the ejected portions of the sun's outer shells surrounding its core remnant (the white dwarf) ............................................................................ White Dwarf The exposed core of a low mass star, the white dwarf is held together by electron degeneracy pressure. On average it has roughly the same radius as Earth but with 50,000 times its mass. White Dwarfs are limited to a maximum mass of 1.4Msun, by the the Chandrasekhar limit. ............................................................................. White Dwarf in a Binary System If a white dwarf is in a binary star system, its gravity may be strong enough to begin accreting the mass of its partner star. As this mass falls on the surface of the white dwarf it may cause a brief ignition of hydrogen resulting in a Novae. If the white dwarf accretes enough matter, it could ignite carbon fusion, resulting the entire dwarf to be destroyed in a white dwarf supernovae. |