Life Cycle of Stars |
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Click one of the phases of the life cycle to learn more |
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Molecular CloudsLarge, dense molecular clouds are very special environments in space. Composed mainly of molecular hydrogen and helium, with small amounts of heavier gases, they are the birth place of new stars and planets. Molecular clouds that exceed the mass of 100,000 suns are called giant molecular clouds. Giant molecular clouds are the largest inhabitants of galaxies, reaching up to 300 light years in diameter. They contain enough dense gas and dust to form hundreds of thousands of Sun-like stars. These stars are formed in the densest parts of the clouds. Molecular clouds are very cold, having temperatures ranging from about -440 to -370 degrees Fahrenheit (-263 to -223 degrees Celcius or 10 to 50 degrees Kelvin). They usually do not radiate their own visible light and appear dark when viewed with an optical telescope. In these cold, dense environments, many atoms can combine into molecules. Giant molecular clouds can last for 10 to 100 million years before they dissipate, due to the heat and stellar winds from newly formed stars within them. An average spiral galaxy, like our own Milky Way, contains about 1,000 to 2,000 Giant Molecular Clouds in addition to numerous smaller clouds. |
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ProtostarsA Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. The protostellar phase is an early stage in the process of star formation. For a solar- mass star it lasts about 100,000 years. It starts with a core of increased density in a molecular cloud and ends with the formation of a T Tauri star, which then develops into a main-sequence. This is heralded by the T Tauri wind, a type of super solar wind that marks the change from the star accreting mass into radiating energy. |
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Main Sequence StarsMain Sequence Stars are like our sun, our sun is in its Main Sequence. Shortly after hydrostatic equilibrium is achieved the star must ignite hydrogen fusion within its core in order to maintain the balance and resist gravity's grasp. If it does not have the mass to do this it will continue to collapse under gravity and cool as it does. Such failed stars are called Brown Dwarfs (3a). Stars like our Sun live for 10 billion years on the main sequence. Stars with higher masses live shorter lives, and stars with less mass live longer lives. The main sequence is where all stars spend the vast majority of their active existences. |
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Red Giant StarsA red giant is a luminous giant star of low or intermediate mass that is in a later phase of its evolution, with nuclear fusion going on in a shell outside the core but not in the core itself. The core matter is electron degenerate and extremely compressed, so the outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower. The appearance of the red giant is from yellow orange to red, including the spectral types K and M, but also class S stars and most carbon stars. Below is a size comparison of a Red Gaint to other stars. |
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Planetary NebulasA planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. The name originates from a similarity in appearance to giant planets when viewed through a small optical telescope, and is unrelated to planets of the solar system. They are a relatively short- lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. About 1,500 are known to exist in the Milky Way Galaxy. |
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SuperNovasA black hole is a region of space in which the gravitational field is so powerful that nothing can escape after having fallen past the event horizon. The name comes from the fact that even electromagnetic radiation (e.g. light) is unable to escape, rendering the interior invisible. However, black holes can be detected if they interact with matter outside the event horizon, for example by drawing in gas from an orbiting star. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation in the process. |
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Black HolesA black hole is a region of space in which the gravitational field is so powerful that nothing can escape after having fallen past the event horizon. The name comes from the fact that even electromagnetic radiation (e.g. light) is unable to escape, rendering the interior invisible. However, black holes can be detected if they interact with matter outside the event horizon, for example by drawing in gas from an orbiting star. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation in the process. |
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