What is the Life Cycle of a Star?
In any case, have a look at http:/ /ast.star.rl.ac.uk/hr.html. This page illustrates the “Hertzsprung-Russell Diagram,” a graphical plot on which astronomers plot the characteristics of stars. In the HR diagram, total brightness (known as “Luminosity” or “Absolute Magnitude”) is plotted against the surface temperature of the star. As the star goes through its life cycle, it moves along the HR diagram from one place to another. The page I sent you shows tracks for stars and “failed stars” like Jupiter. The star begins as a cool cloud of gas, well to the right (cold side) of the diagram. Under its own gravity, the cloud begins to collapse. As it collapses, it releases its gravitational energy as radiation. So a young star is cool but bright. We usually don’t see these proto-stars, however, because they are generally shrouded in dust and only give off light in the far infrared part of the spectrum. The proto-star continues to collapse, and as it does, it gets hotter and hotter, moving to
Stars are born, stars grow old, stars die! The life cycle of a star is actually a struggle between gravity and gas pressure, which is known as the equilibrium. Majority of the life of a star is spent in a stage known as the main sequence. Stars fuse hydrogen, and when the hydrogen fuel is gone, they fuse helium into carbon. A star is a sizzling mass of gas. It is composed of the inner core housing the process of fusion and an outer gaseous shell. The core is hot and dense, serving as the gravitational center of a star. The outer shell, made of hydrogen and helium, facilitates the transfer of heat from the core of the star to its surface. Light and heat energy is released into space from the surface of the star. Life Cycle of a Star • Stars are born in the nebulae, which are huge clouds of gas and dust. The matter contained in the nebula determines the mass of the star. The clouds of gas and dust disintegrate under the force of gravity. Gravitational forces make the nebula spin. As it s
A star begins as a cloud of interstellar gas, mostly made of hydrogen. Eventually, small density differentials begin the cloud begin to create gravity wells, pulling other particles closer and condensing them. Over time, this process of compaction creates a spherically-shaped central cloud, orbited by the gas on the fringes, creating what is called an accretion disk. The critical step in the birth of a star is the creation of density levels sufficient to initiate hydrogen fusion. Fusion brings together atomic nuclei lighter than that of iron, releasing energy in the process. The first atoms to fuse in a condensing star-cloud are probably deutrium atoms, an isotope of hydrogen with one neutron. Despite their scarcity relative to conventional hydrogen, they require a lower temperature and pressure to fuse and therefore would probably get started first. Fusing atomic nuclei is difficult to achieve because of the electrostatic repulsion caused by the electron shells of both atoms. After th
THE LIFE CYCLE OF A STAR Outlined below are the many steps involved in a stars evolution, from its formation in a nebula, to its death as a white dwarf or neutron star. NEBULA A nebula is a cloud of gas (hydrogen) and dust in space. Nebulae are the birthplaces of stars. There are different types of nebula. An Emission Nebula e.g. such as Orion nebula, glows brightly because the gas in it is energised by the stars that have already formed within it. In a Reflection Nebula, starlight reflects on the grains of dust in a nebula. The nebula surrounding the Pleiades Cluster is typical of a reflection nebula. Dark Nebula also exist. These are dense clouds of molecular hydrogen which partially or completely absorb the light from stars behind them e.g. the Horsehead Nebula in Orion. Planetary Nebula are the outer layers of a star that are lost when the star changes from a red giant to a white dwarf. STAR A star is a luminous globe of gas producing its own heat and light by nuclear reactions (nu
