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Stellar Evolution: The Life and Death of Our Luminous Neighbors. by Arthur Holland and Mark Williams. Introduction and Why You Should Care. Observations of. The process of change that a star undergoes during its lifetime is called stellar evolution. But this process can take millions or billions of years. Stellar Evolution. All stars form from clouds of gas and dust condensing in deep space. Only the chemical composition of this cloud, and the amount of material in.
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A star about he same mass as the Sun will first become a red giant before ejecting its outer atmosphere, enriched with elements it has made, into the space between the stars.
There the matter will be ready stellar evolution form a new generation of stars, while the Sun becomes a white dwarf stellar evolution slowly fades away.
If the star is more massive than this, the ignition of the core is more gentle. At the same time, the star continues to burn hydrogen in a shell around stellar evolution core.
The star burns helium into carbon in its core for a much shorter time than it burned hydrogen.
Once the helium has all been converted, the inert carbon core stellar evolution to contract and increase in temperature. This ignites a helium burning shell just above the core, which in turn is surrounded by a hydrogen burning shell.
Stellar Evolution | COSMOS
What happens next depends on the mass of the star Stars less than 8 solar masses The inert carbon core continues to contract but never reaches temperatures sufficient to initiate carbon burning.
This instability to collapse means that no white stellar evolution more massive than approximately 1. Mass transfer in a binary system may cause an initially stable white dwarf to surpass the Chandrasekhar limit.
If a white dwarf forms a close binary stellar evolution with another star, hydrogen from the larger companion may accrete around and onto a white dwarf until it gets hot enough to fuse in a runaway reaction at its surface, although the white dwarf remains below the Chandrasekhar limit.
Such an explosion is termed a nova. Neutron star Bubble-like shock wave still expanding from a supernova explosion 15, years ago. Ordinarily, atoms are mostly electron clouds by volume, with very compact nuclei at the center proportionally, if atoms were the size of a football stadium, their nuclei would be the size of dust mites.
Gravity and Stellar Evolution
When a stellar core collapses, the pressure causes electrons and protons to fuse stellar evolution electron capture. Without electrons, which keep nuclei apart, the stellar evolution collapse into a dense ball in some ways like a giant atomic nucleuswith a thin overlying layer of degenerate matter chiefly iron unless matter of different composition is added later.
The neutrons resist further compression by the Pauli Exclusion Principle, in a way analogous to electron degeneracy pressure, but stronger.
Their period of rotation shortens dramatically as the stars shrink due to conservation of angular momentum ; observed stellar evolution periods of neutron stars range from about 1.
Such neutron stars are called pulsarsand were the first neutron stars to be discovered.
Though electromagnetic radiation detected from pulsars is most often in the form of radio waves, pulsars have also been detected at visible, X-ray, and gamma ray wavelengths. Black hole If the mass stellar evolution the stellar remnant is high enough, the neutron degeneracy pressure will be insufficient to prevent collapse below the Schwarzschild radius.
The stellar remnant thus becomes a black hole. Black holes are predicted by the theory of general relativity. According to classical general relativity, no matter or information can flow from the interior of a black hole to an outside observer, although quantum effects may allow deviations from this strict rule.
The existence of black holes in the universe is well supported, both theoretically and by astronomical observation. Because the core-collapse mechanism of a supernova is, at present, only partially understood, it is still not known whether it is possible for a star to collapse directly to a black hole without producing stellar evolution visible supernova, or whether some supernovae initially form unstable neutron stars which then collapse into black holes; the exact relation between the initial mass of the star and the final remnant is also not completely certain.
But if the collapsing core of the star is very great -- at least three times the mass of the Sun -- nothing can stop the collapse.
- NASA - Stellar Evolution - The Birth, Life, and Death of a Star
- Stellar evolution - Wikipedia
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The star implodes to form an infinite gravitational warp in space -- a black hole. The following diagram shows the dramatic stellar evolution of a main sequence star as it begins helium fusion. A Star in Old Age. Temperature within the core of stars greater than three solar masses soon exceeds the million Kelvin degrees barrier, at which it reaches the temperature needed for the onset of helium fusion.
With gravitational contraction halted, the heat and energy from the core helium burning again begins the expansion of the star's outer layers.