I’m Feeling Stellar: The study of stars and stellar evolution is fundamental to our understanding of the Universe. The astrophysics of stars has been determined through observation and theoretical understanding, and from computer simulations of the interior.
Star formation occurs in dense regions of dust and gas, known as giant molecular clouds. When destabilized, cloud fragments can collapse under the influence of gravity, to form a protostar. A sufficiently dense, and hot, core region will trigger nuclear fusion, thus creating a main-sequence star.
Stellar evolution
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 refers as nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what refers as a main-sequence star.
Almost all elements heavier than hydrogen and helium were created inside the cores of stars.
characteristics of the resulting star
The characteristics of the resulting star depend primarily upon its starting mass. The more massive the star, the greater its luminosity, and the more rapidly it fuses its hydrogen fuel into helium in its core. Over time, this hydrogen fuel completely converted into helium, and the star begins to evolve.
The fusion of helium requires a higher core temperature. A star with a high enough core temperature will push its outer layers outward while increasing its core density.
The resulting red giant formed by the expanding outer layers enjoys a brief life span, before the helium fuel in the core is in turn consumed. Very massive stars can also undergo a series of evolutionary phases, as they fuse increasingly heavier elements.
The final fate of the star depends on its mass, with stars of mass greater than about eight times the Sun becoming core collapse supernovae; while smaller stars blow off their outer layers and leave behind the inert core in the form of a white dwarf.
Planetary nebula – I’m Feeling Stellar
The ejection of the outer layers forms a planetary nebula. The remnant of a supernova is a dense neutron star, or if the stellar mass was at least three times that of the Sun, a black hole. Closely orbiting binary stars can follow more complex evolutionary paths, such as mass transfer onto a white dwarf companion that can potentially cause a supernova.
Planetary nebulae and supernovae distribute the “metals” produced in the star by fusion to the interstellar medium; without them, all new stars (and their planetary systems) will form from hydrogen and helium alone.
I’m Feeling Stellar – Black Hole
A black hole is a region of spacetime where gravity is so strong that nothing. No particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape refers the event horizon.
Although it has an enormous effect on the fate and circumstances of an object crossing it. According to general relativity it has no locally detectable features. For Further Detail implogs.com
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