Biology Forums - Study Force

Can any one make me clear in this confusion with a definition for each [?-?]

Cosmos: an alternative name for the universe.

Nebula: a cloud of gas in space, usually one that is glowing.

Galaxy: a huge collection of anywhere from a few hundred million to more than a trillion stars, all bound together by gravity.

Source: The Cosmic Perspective 6th Edition

Thanks,Then Can i say nebula is also a part of galaxy ?

Can i say nebula is also a part of galaxy ? or a galaxy may have a nebula?

Originally, the word "nebula" referred to almost any extended astronomical object (other than planets and comets). The etymological root of "nebula" means "cloud". As is usual in astronomy, the old terminology survives in modern usage in sometimes confusing ways. We sometimes use the word "nebula" to refer to galaxies, various types of star clusters and various kinds of interstellar dust/gas clouds. More strictly speaking, the word "nebula" should be reserved for gas and dust clouds and not for groups of stars.

A nebula is technically a cloud of gas or dust in space while a galaxy is a much larger structure of billions of stars, usually including many smaller nebulae. However, in some older astronomy literature, all "fuzzy objects" were called nebulae, even if they were technically galaxies. This is because scientists had not yet established that galaxies were, in fact, objects outside the Milky Way. They were presumed to be among the local gas & dust objects in our own galaxy. Edwin Hubble made the essential determination that some "nebulae" were considerably further away than other objects in the milky way and were, in fact, separate galaxies.

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