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From a very early age, we are taught about the stars and planets in our solar system. These concepts have become so ingrained in our minds that it isn’t often we stop to think about how and why things are the way they are. Who decided Jupiter is Jupiter and not Saturn? Who decided we should call our closest star the Sun and not the Moon? 

To understand how the planets in our solar system got their names, it’s important to understand where some of the names in stem from. Well-known planets, such as Mercury and Mars, were named from Greek and Roman mythology. Mercury was named after the god of commerce, travel and thievery in Roman mythology, most likely due to its speed moving across the sky. Venus is a bright planet that is only outshone by the Moon and the Sun; it is likely because of this that it was named after the Roman goddess of love and beauty. Saturn is named after the Roman god of agriculture, while Uranus is named after the ancient Greek deity of the Heavens. Mars was named after the Roman god of war, Pluto after the Roman god of the underworld, and Jupiter was named after the King of the Gods in Roman Mythology. Earth is the only planet whose English name does not derive from Greek/Roman mythology. Instead, it was derived from Old English and Germanic. There are also many names for the Earth in other languages.

The naming scheme began about a century ago when an international cooperation union was formed to regulate asteroid names, as well as planets, minor planets, comets, moons and geographical features on planets and moons, such as craters. The International Astronomical Union (IAU) was formed in 1919 when a new naming system was desperately needed. At the time, objects weren’t often cross-checked, there was a real lack of any records, and there were no consistent patterns for naming celestial objects. Once the IAU was formed, astronomers had to piece together global records, and in some cases, rediscover asteroids. Because this freeform naming system led to such scientific confusion, the IAU was formed to avoid any future uncertainty. 

Gareth Williams, an astronomer at the Harvard-Smithsonian Center for Astrophysics who serves as associate director of the IAU’s Minor Planet Center and helps with determining potential planet names, shared how carefully regulated the IAU process is. For what can be months-long at a time, the committees look over proposals to ensure that no newly discovered object is double-named and that no offensive or inappropriate names sneak through.

Today, the IAU has weighed in to formally approve names for a few hundred well-known stars. Stars in named constellations that are visible to the naked eye are typically given a letter of the Greek alphabet according to their position within their constellation. However, there are far more stars in the universe than we could ever come up with names for. In fact, researchers have reported that there could be 2 trillion galaxies in the observable universe, each containing an untold number of suns. So rather than discerning a name for all, the IAU settled on giving every star a number.