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Apr 11, 2022 · Eventually, as stars age, they evolve away from the main sequence to become red giants or supergiants. The core of a red giant is contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core. The star gets larger, redder, and more luminous as it expands and cools.
- Star Clusters
Star clusters provide one of the best tests of our...
- Star Clusters
Apr 11, 2022 · During this time, a newly formed carbon nucleus at the center of the star can sometimes be joined by another helium nucleus to produce a nucleus of oxygen—another building block of life. Figure 22.4.1 22.4. 1 Evolution of a Star Like the Sun on an H–R Diagram. Each stage in the star’s life is labeled.
Models. A stellar evolutionary model is a mathematical model that can be used to compute the evolutionary phases of a star from its formation until it becomes a remnant. The mass and chemical composition of the star are used as the inputs, and the luminosity and surface temperature are the only constraints.
It then gradually fades away over many months. After a supernova occurs, a small remnant of the star’s core, made only of neutrons, is left over. This is called a neutron star. A neutron star has a mass of about 1.4 times the mass of the Sun, but is only about 20 km (12.4 miles) in diameter.
The star now has a multi-layered structure like an onion: a carbon-oxygen core, surrounded by a shell of helium fusion, a layer of helium, a shell of hydrogen fusion, and finally, the extended outer layers of the star (see Figure 22.17). As energy flows outward from the two fusion shells, once again the outer regions of the star begin to expand.
May 7, 2015 · A star's life cycle is determined by its mass. The larger its mass, the shorter its life cycle. A star's mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust from which it was born. Over time, the hydrogen gas in the nebula is pulled together by gravity and it begins to spin.
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Over the course of time, again long by human though short by stellar standards, a star of normal size and yellow color slowly changes into one of giant size and red color. The bright normal star has evolved into a dim red-giant star. Figure 3.25 compares the relative sizes of our Sun and a red-giant star.
