Q: What is galaxy? The Earth belongs to which galaxy? (CSS 2011)
Galaxy
A galaxy is a large scale aggregate of stars, plus some gas, dust, and possibly. Solar systems, which are held together by gravity.
Early astronomers would look into the Universe with Their telescopes and notice “milky” areas that they could not be defined as one star. Sir William Herschel, in the late 1700’s, counted stars and recorded them, developed a notion of the Galaxy. The Galaxy referred to our own Milky Way with its billions of stars, with our Sun and planets being a component. Other galaxies were found throughout the Universe. These islands of stars had different shapes and sizes. The Andromeda Galaxy is spiral, and is larger than our Milky Way Galaxy.