The word nebula has its origin in Latin. The Latin word nebula was adapted by Middle English as nebule which means cloud or mist. A nebula is a mass of dust and gas. It could also consist of only dust of gas. But, this diffuse mass is seen as a bright and luminous areas or patches of darkness. The mass differs in its absorption or reflection of the incident radiation. Thus, it results in the darkness and luminosity of a nebula. A galaxy could also be termed as a 'nebula'.Thanks.
A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy was referred to as the Andromeda Nebula before galaxies were discovered by Edwin Hubble). Nebulae are often star-forming regions, such as in the Eagle Nebula. This nebula is depicted in one of NASA's most famous images, the "Pillars of Creation". In these regions the formations of gas, dust, and other materials "clump" together to form larger masses, which attract further matter, and eventually will become massive enough to form stars. The remaining materials are then believed to form planets, and other planetary system objects.
the word "nebula" referred toany extended astronomical object (other than planets and comets). We sometimes use the word "nebula" to refer to galaxies, various types of star clusters and various kinds of interstellar dust/gas clouds.
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