1) Planets outside of our solar system are named after the star that they orbit, plus a lower case letter. The first planet discovered orbiting a star is assigned the letter "b" (the parent star is "a"). The closet known exoplanet is Proxima Centauri b. If another planet is found orbiting Proxima Centauri, that planet will likely be named Proxima Centauri c. A third planet would be called Proxima Centauri d. The letters are assigned in order of discovery, not in the order of the distance from their parent star.
So if we applied that naming system to our solar system, this is how it would work: You step out of your house and you discover a big yellow star overhead. You name it "Sol". You look down and you see that you are standing on a planet. You name it "Sol b". Sol a sets below the horizon, and you might see Sol c (Venus, usually the first thing you see in the night sky besides the moon) and Sol d (Mercury). After about an hour or so, you might notice Sol e, Sol f, and Sol g. (Mars, Jupiter, and Saturn, depending on the order that you find them.) On a really clear night, you might see Sol h with the naked eye (Uranus), but you'll probably need at least a pair of binoculars. With a decent telescope, you can see Sol i (Neptune).
Why don't scientists give each planet its own name? Because not even all known stars have a name. Most of them get serial numbers. Hell, not even all people get their own name. Ever meet a family with men named "Francis Matherford IV" and "Roger Croningsworth VII"? Maybe if those people spend less money on yachts, they could afford a baby name book.
As far as I know, ALWFT is the first science fiction novel to use the same naming standard for exoplanets as the International Astronomical Union.
2) Place names on Earth do change. England used to be called Albion. New York was once New Amsterdam. Anyone who listens to 80's music knows what Istanbul used to be called. Part of ALWFT takes place in the Kekionga Municipal District, a city formally known as Fort Wayne. Enough people saw Planet of the Apes and agreed with Dr. Zaius that the name was too militaristic, so the name was finally changed.
3) The closet galaxy to Earth (aside from the Milky Way itself) might be what is known as the Canis Major Dwarf Galaxy. At 28,000 years away, it's actually closer to us than the opposite side of the Milky Way. If FTL travel is developed, humans might reach the Canis Major Dwarf Galaxy before the Milky Way is fully explored. If there are to be human settlements there, they'll have to change the name of that galaxy to avoid offending little people and for marketing purposes. "New Magellanic Cloud" is one possible name.
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