The article explores the definition of a galaxy, indicating that, while galaxies are often described as systems of stars, gas, dust, and dark matter held by gravity, this description is not universally applicable. Many galaxies lack certain components. The term 'galaxy' comes from the Greek word for the Milky Way, reflecting our understanding that these massive structures vary greatly in size, luminosity, and composition. The Milky Way, for instance, measures approximately 120,000 light-years across and houses between 100 billion to 400 billion stars, emphasizing the vast complexity of these cosmic entities.
The term 'galaxy' derives from the ancient Greek 'galaktikos kyklos,' meaning 'milky circle,' referring to the Milky Way, our home galaxy.
While galaxies generally comprise stars, gas, dust, and dark matter, defining them becomes tricky since not all galaxies contain every feature.
Galaxies vary in size and star count; for example, the Milky Way spans about 120,000 light-years and contains between 100 to 400 billion stars.
The complexity of galaxies defies simple definitions, mirroring the challenges faced in defining other cosmic entities like planets and moons.
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