Neptune is the most distant planet in the Solar System, around 30 times farther from the Sun than we are. It would make sense for it to be the coldest out of all the planets, but here comes the surprise: it's not. In 1989, NASA's spaceship Voyager 2 passed by both Uranus and Neptune and found that Neptune was warmer than its neighbor, even though it was farther away from the Sun. 

Scientists came up with a bunch of theories trying to explain this staggering discovery. Let's try to understand what's really going on with Neptune.

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