![]() ![]() This stage lasts approximately 500,000 years. Very young stars called “protostars” gather mass from the gas and dust around them in their natal cloud. The life of every star starts in interstellar clouds. After that, they will enter a different phase as they become nearer the end of their stellar evolution. Stars spend thousands to a billion years in the red giant stage. Those in the horizontal branch have about 75 solar luminosities. The luminosity of stars in the red giant branch is about three thousand times greater than the solar luminosity. In the Hertzsprung–Russell diagram (HR diagram), the roman numerals II and III correspond to the luminosity class of bright giants and giants respectively. They are greater in size which is why they are more luminous than our Sun. ![]() A carbon star has more carbon while an S star has about an equal amount of oxygen and carbon in its atmosphere.Īfter the main sequence, stars with a mass of approximately 0.8 to 8 solar masses will become red giants. They differ in the amount of carbon and oxygen in their atmospheres. Other stars that belong in this type are carbon stars and S-type stars. They have a yellow-orange to red appearance, an indication of a cooler surface temperature. Red giant stars are in the K and M spectral class. Lifespan: A few thousand to one billion years Spectral class: K or M type (including carbon stars and S-type) Some notable examples of red giants are Arcturus, Aldebaran, Gacrux, Pollux, and Mira. Before their lights fade out, they will eject glowing shells of gas called planetary nebulae. Their life cycle is also an interesting one. Red giant stars are some of the biggest and most luminous stars in our night sky. Their cores are made up of carbon and oxygen as well as helium-burning and hydrogen-burning shells. Cool and luminous stars populate the AGB. In the HB, helium is fused in the cores of red giants through the triple-alpha process. Red giants are commonly on the RGB where they fuse hydrogen into helium through the shell that surrounds the helium core. There are three groups of them in the giant branch: the red-giant branch (RGB), the horizontal branch (HB), and the asymptotic-giant-branch (AGB). Red giant stars have different ways of generating their energy. As its name stays, a red giant is a K or M-type star. It will stay in this stage for about 10 billion years before it becomes a red giant star. This balance is established because of nuclear fusion reactions in its core. In the main sequence, the core of a star is in a state of hydrostatic equilibrium. It generates energy by converting hydrogen into helium. It is said that stars only spend 1% of their lives in this stage. A red giant is a star in the later stages of its stellar life. ![]()
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