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Vast Nebula

Vast Nebula (Picture 1)


Nebula is one of the celestial bodies composed of thin gas or dust. Contains almost all extended celestial bodies except planets and comets. Their main component is hydrogen, followed by helium, and also contains a certain proportion of metallic and non-metallic elements. Studies since the Hubble Telescope took off in 1990 have also found that it contains organic molecules and other substances. Compared with stars, nebula has the characteristics of large mass, large volume and low density. The mass of an ordinary nebula is at least equivalent to thousands of suns, and its radius is about 10 light years. Nebulae are also usually areas where stars are formed, such as the Eagle Nebula. This nebula portrays NASA's most famous image: the Pillar of Creation. The gas, dust, and other materials that formed in this area squeezed together, gathered a huge mass, which attracted more mass, and finally large enough to form stars. It is understood that the remaining material can also form planets and other celestial bodies of planetary systems.

The nebula is a cloud-like object composed of gas and dust in interstellar space. The density of matter in the nebula is very low. If measured by the standards on the earth, some places are vacuum. However, the nebula is very large, often reaching a few dozen light years. Therefore, the general nebula is much heavier than the sun. The shape of the nebula is diverse. Nebula and stars have a "blood relationship" relationship. The gas ejected by the star will become part of the nebula, and the matter of the nebula will be compressed into a star under the action of gravity. Under certain conditions, the nebula and stars can be transformed into each other. People even suspect that stars are formed by "condensation" of interstellar gas. Interstellar dust is some very small solid matter, and its components include carbon compounds and oxides. 10-100 atoms per cubic centimeter (in fact this is much lower than the vacuum obtained in the laboratory).

The planetary nebula looks like a spitting smoke ring, the center is empty, and there is often a very bright star. The star continuously ejects matter outward, forming a nebula. It can be seen that the planetary nebula is the result of the evolution of stars in their later years. More famous are the Auricular Nebula Nebula and the Lyra Nebula. The material density of the nebula is very thin, and the main component is hydrogen. According to theoretical calculations, when the density of the nebula exceeds a certain limit, it must shrink under the action of gravity, and the volume becomes smaller, and gradually gathers into clusters. It is generally believed that a star is formed by the nebula contracting, gathering, and evolving under the action of gravity during its motion. After the star is formed, it can throw a lot of material into interstellar space and become a part of the raw material of the nebula. Therefore, under certain conditions, stars and nebulae can be transformed into each other.

When we refer to cosmic space, we often think of a vacuum of darkness and silence. In fact, this is not entirely true. The vast expanse of space between stars may be silent, but it is far from a real "vacuum", but there is a variety of matter. These substances include interstellar gas, dust, and particle streams, and they are called "interstellar matter". Interstellar matter is closely related to the evolution of celestial bodies. Observations confirmed that interstellar gas is mainly composed of two elements, hydrogen and nitrogen, which is the same as the composition of stars. In fact, stars are formed by "condensation" of interstellar gas. Interstellar dust is some very small solid matter, and its components include carbon compounds and oxides. The distribution of interstellar matter in the universe is not uniform. Under the action of gravity, the gas and dust in some places may attract each other and become dense, forming a cloud shape. People vividly call them nebula. According to the shape, the nebula in the Milky Way can be divided into diffuse nebula, planetary nebula and so on.

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