The nebula is one of the thin gas or dust composed of a thin gas or dust. Almost all extended celestial bodies except the planets and comets. The main ingredients are hydrogen, followed by helium, and also contains a proportion of metal elements and non-metallic elements. The study since the 1990 Hubblels has also found that organic molecules and other substances. Compared with the star, the nebula has the characteristics of large quality, large volume and small density. An ordinary nebula is at least equivalent to thousands of sun, and the radius is approximately 10 light years. Nebula is usually also the area formed by stars, such as Eagle Clouds. This nebol is drawn from NASA's most famous image: the column of the creation. In this area, the gas, dust and other materials are crowded together, gathered great quality, which attracts more quality, and finally enough to form a star. It is understood that the remaining materials can also form other celestial bodies of planets and planets.
The nebula is a cloud-like sky that is bonded by gas and dust in the interstellar space. The material density in the nebula is very low. If the standard on the earth is measured, some places are vacuum. But the size of the nebula is very large, often reaches a few tens of light years. Therefore, general nebula is much more than the sun. The shape of the nebula is a polymorphic. Nebula and stars have a "blood" relationship. The gases thrown in the star will become part of the nebula, and the nebula is compressed into a star under gravity. Under certain conditions, nebula and stars are capable of transforming each other. People even guess, the star is made by the interstellar gas "condense". Star dust is some small solid matter, and the components include carboys, oxides, and the like. Each cubic centimeter is 10-100 atoms (in fact, this is much lower than the vacuum obtained in the laboratory).
The planetary nebula is a bit like a smoke ring, the center is empty, and there is often a very bright star. The stars continue to project abroad and form a nebula. It can be seen that the planetary nebula is the result of the elevation of starry old age. More famous with bottlett ear wheels nebula and Tianqin ring nebula. The laminar density of the nebula is very thin, the main component is hydrogen. According to the theory, the density of the nebula exceeds a certain limit, and it is necessary to shrink under the action of gravity, the volume is small, and the group is gradually collected. It is generally considered that the star is the nebula in the exercise process, shrinks, aggregates, and evolves under the action. After the star formation, it can also project a large amount of the substance to the interstellar space, and become a part of the raw material of the nebula. Therefore, stars and nebes can be transformed with each other under certain conditions.
When we mentioned the space space, we will often think that there is no, dark and quiet vacuum. In fact, this is incomplete. There is a quiet space between the stars, but it is not a real "vacuum", but there are various substances. These substances include interstellar gases, dust and particle flow, etc., people call them "Star Substances". Star substances have a close relationship with the evolution of the celestial body. Observing confirmed that the intersectant gas is mainly composed of two elements of hydrogen and nitrogen, which is the same as the ingredient of the star. In fact, the star is made by the interstellar gas "condense". Star dust is some small solid matter, and the components include carboys, oxides, and the like. The distribution of interstellar substances in the space of the universe is not uniform. Under gravitational action, some places of gas and dust may be attracted to each other and form a cloud shape. People call them nebula. According to the form, the nebula in the Milky Way can be divided into a few kinds of abuse clouds and planetary nebula.