The 65.438+0.7 billion pixel panorama of the Milky Way has amazed netizens. How are nebulae formed?

How are nebulae formed? Nebulae have many forming mechanisms. Some nebulae are formed by gas in interstellar medium, while others are produced by stars. The former example is a huge and broad molecular cloud, which needs to be in the coldest and densest stage of interstellar gas and can be formed by cooling and condensing more diffused gas. An example of the latter case is the planetary nebula, which is made up of stars that evolved later? Blow it out? The substance.

Nebula, as its name implies, is a kind of? Cloud? , similar to the earth in the sky? Cloud? . The nebula here means that from the earth's point of view, there is a piece in the deep sky similar to that in the earth's atmosphere? Cloud? Like a substance. Does it really exist? Star? Embodied in this word, this piece is the birth area of stars. This article will give you a brief introduction? Nebula? The concept of astronomical definition.

Brief introduction of nebula concept

Nebula is an interstellar cloud composed of dust, hydrogen, helium and other ionized gases. Initially, the definition of nebula was the general name of any diffuse celestial body, including galaxies outside the Milky Way. For example, Andromeda galaxy was once called Andromeda nebula (and spiral galaxy, commonly known as? Spiral nebula? ), before that, in the early 20th century, Vesta Slipher and Edwin Hubble and others confirmed the nature of galaxies.

The star-forming region is an emission nebula related to a huge molecular cloud. These forms of molecular clouds collapse under their own weight and begin to form protostars. Massive stars may form in their centers, and their ultraviolet radiation will ionize the surrounding gases, making them visible at optical wavelengths. The ionized hydrogen region around the massive star is called the H II region, while the neutral hydrogen shell around the H II region is called the photodissociation region (or photon control region, or PDRs). At present, the observed examples of star forming regions are Orion Nebula (M42), Rose Nebula and Omega Nebula (M 17). Feedback from star formation, such as supernova explosion of massive stars, stellar wind or ultraviolet radiation of massive stars, or outflow of low-mass stars, may destroy the nebula, or even destroy the entire nebula structure millions of years later. However, other nebulae are the result of supernova explosions.