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Life Cycle Of Stars
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star. Nuclear fusion powers a star for most of its existence. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Representative Lifetimes Of Stars As A Function Of Their Masses
Representative may refer to: Politics *Representative democracy, type of democracy in which elected officials represent a group of people *House of Representatives, legislative body in various countries or sub-national entities *Legislator, someone who is a member of a legislature Mathematics *Representative (mathematics), an element of an equivalence class representing the class Other uses *Sales representative *Manufacturers' representative *Customer service representative *Holiday rep *Representative sample, in statistics a sample or subset meant to represent a population *Representative director (Japan), most senior executive in charge of managing a corporation in Japan * ''The Representative'' (newspaper), unsuccessful 1826 London newspaper See also * * Representation (other) *Rep (other) * Presentative (other) *Special Representative Diplomatic rank is a system of professional and social rank used in the world of diplomacy and internationa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Luyten in 1922. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red gi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
