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Biggest main sequence star11/14/2023 ![]() ![]() The ejected material remains as a planetary nebula, radiating as it absorbs energetic photons from the photosphere. Expanding even further as helium starts running out as it pulses violently, the star's gravity is not sufficient to hold its outer envelope, resulting in significant mass loss and shedding. After this, the star's degenerate helium core abruptly ignites in a helium flash fusing helium, and the star passes on to the horizontal branch, and then to the asymptotic giant branch. ![]() When this happens, the star rapidly expands, cooling and darkening as it passes through the subgiant branch and ultimately expanding into many times its previous size at the tip of the red giant phase, about 1 billion years after leaving the main sequence. Ī G-type main-sequence star with the mass of the Sun will fuse hydrogen for approximately 10 billion years, until the hydrogen element is exhausted at the center of the star. In addition, although the term "dwarf" is used to contrast G-type main-sequence stars with giant stars or bigger, stars similar to the Sun still outshine 90% of the stars in the Milky Way (which are largely much dimmer orange dwarfs, red dwarfs, and white dwarfs which are much more common, the latter being stellar remnants). The Sun is in fact white, but it can often appear yellow, orange or red through Earth's atmosphere due to atmospheric Rayleigh scattering, especially at sunrise and sunset. The term yellow dwarf is a misnomer, because G-type stars actually range in color from white, for more luminous types like the Sun, to only very slightly yellowish for less massive and luminous G-type main-sequence stars. Besides the Sun, other well-known examples of G-type main-sequence stars include Alpha Centauri, Tau Ceti, and 51 Pegasi. Each second, the Sun fuses approximately 600 million tons of hydrogen into helium in a process known as the proton–proton chain (4 hydrogens form 1 helium), converting about 4 million tons of matter to energy. The Sun, the star in the center of the Solar System to which the Earth is gravitationally bound, is an example of a G-type main-sequence star (G2V type). Like other main-sequence stars, a G-type main-sequence star converts the element hydrogen to helium in its core by means of nuclear fusion, but can also fuse helium when hydrogen runs out. Such a star has about 0.9 to 1.1 solar masses and an effective temperature between about 5,300 and 6,000 K. Stellar classification The Sun, a typical example of a G-type main-sequence starĪ G-type main-sequence star (spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main-sequence star (luminosity class V) of spectral type G. ![]()
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