Pluto

Once classified as a planet in 1930 by discoverer Clyde Tombaugh, Pluto is a dwarf planet located in the Kuiper Belt roughly 39 AU from the Sun, or Sol. The dwarf planet was visited by the New Horizons space probe on 14th July 2015, sending the first images of Pluto back to NASA. It is classified as a frigid arid miniaquaria.

Discovery

Pluto was discovered during the search for a Planet X, a planet believed to have been gravitationally tugging on Neptune's orbit. Although Pluto is not massive enough to do this, Pluto was essentially classified as the ninth planet for 76 years until 2006 when the IAU reclassified it as a dwarf planet, after the discovery of objects like Pluto in the Kuiper Belt, such as Eris, Makemake, Haumea and hundreds more.

Young man Clyde Tombaugh was the discoverer of the dwarf planet Pluto on February 28th, 1930. It was the first "planet" to be discovered within a century of Neptune's discovery in 1846.

Atmosphere

Pluto has a very thin but noticeable atmosphere of mostly nitrogen with some methane. It can only be detected when the dwarf planet occults a bright star. At its closest point to Sol, the atmosphere is temporarily produced from the ice on the surface. As it gets further away, the atmosphere collapses back on to the surface for decades until the next perihelion.

Space Exploration

Although it remained a mystery for decades, NASA launched the New Horizons space probe on January 19th, 2006 and arrived at Pluto, roughly 9 years later on 14th July 2015 where it made a close approach to the dwarf planet to collect data about its surface, atmosphere, composition, and moons.

NASA and other space companies launched the Kuiper Belt Exploration Program in 2045 in order to establish more human colonies in the Solar System. It also allowed for the excessive mining of asteroids in the Kuiper Belt which gave supplies to the new colonies in the outer Solar System.

A colony was established on Pluto in 2370, some time after the invention of the Warp Drive. However, in 2990 the colonies, which consisted of around 100,000 humans living in domed cities by this time, were relocated by the UFSS. The explanation given was that the planet was the perfect distance to perform weapons tests. The entire world was then cornered off after the formation of the UFSS.

As Sol passes behind Pluto, it's thin nitrogen atmosphere can be seen.

Moons

Pluto is orbited by five moons, one large moon, called Charon, and four other asteroid moons, perhaps captured or formed with Pluto in the early Solar System. Pluto and Charon are massive enough to create a binary planet while the four other moons orbit the barycenter, which resides outside Pluto, not inside the dwarf planet.

Charon, the largest moon of Pluto, orbits and rotates every 6.3 days.

Charon was later colonized by the Kuiper Belt Exploration Program. Like Pluto, the colonists were forcibly relocated by the UFSS at the same time as Pluto to one of Neptune's moons.