Solar System

**The Solar System** is the gravitationally bound system of the Sun and the objects that orbit it, it contains 8 planets, 5 explored dwarf planets and countless small bodies such as asteroids, comets, and more. The system is a single-star system containg only 1 star, the Sun. The system is also the capital of "United Systems of Milky Way".

## **Formation**

A massive concentration of interstellar gas and dust created a molecular cloud that would form the sun's birthplace. Cold temperatures caused the gas to clump together, growing steadily denser. The densest parts of the cloud began to collapse under its own gravity, forming a wealth of young stellar objects known as protostars. Gravity continued to collapse the material onto the infant object, creating a star and a disk of material from which the planets would form. When fusion kicked in, the star began to blast a stellar wind that helped clear out the debris and stopped it from falling inward.

After the sun formed, a massive disk of material surrounded it for around 100 million years. That may sound like more than enough time for the planets to form, but in astronomical terms, it's an eye blink. As the newborn sun heated the disk, gas evaporated quickly, giving the newborn planets and moons only a short amount of time to scoop it up.

## **Inner Solar System**

The inner Solar System is a region of the Solar System that contains 4 rocky planets:

**Mercury** is the closest planet to the Sun and on average, all seven other planets. The smallest planet in the Solar System, Mercury has no natural satellites. Besides impact craters, its only known geological features are lobed ridges or rupes that were probably produced by a period of contraction early in its history. Mercury's very tenuous atmosphere consists of atoms blasted off its surface by the solar wind. Its relatively large iron core and thin mantle have not yet been adequately explained. Hypotheses include that its outer layers were stripped off by a giant impact, or that it was prevented from fully accreting by the young Sun's energy

**Venus** is close in size to Earth and, like Earth, has a thick silicate mantle around an iron core, an atmosphere, and evidence of internal geological activity. It is much drier than Earth, and its atmosphere is 90 times as dense. Venus has no natural satellites. It is the hottest planet, with surface temperatures over 673 K(400 °C), most likely due to the amount of greenhouse gases in the atmosphere. No definitive evidence of current geological activity has been detected on Venus, but it has no magnetic field that would prevent depletion of its substantial atmosphere, which suggests that its atmosphere is being replenished by volcanic eruptions.

**Earth** is the homeworld of the human species, located in the Solar System. It is the namesake of the Earth Like World classification of Terrestrial Planets. It is the third planet of the system, orbiting at precisely 1 AU from its parent star, a G2-V Main Sequence star The Sun. Earth is the largest of the system's terrestrial and rocky bodies. The planet and its single moon were born from an accretion disk that existed during the Sol System's formation, which happened around 4.5 billion years ago. It has one natural satellite, known simply as "The Moon", or less commonly as "Luna".

Mars, once a hostile radioactive desert now successfully terraformed into a lush planet filled with forests, bottomless oceans and all sorts of creatures that live there. It is truly a sight for everyone, it was colonized in the early 25th century, some of its old terrain is still preserved, like Olympus Mons, the tallest mountain in the Solar System which is visible even from space.

## **Asteroid belt**

The Asteroid belt is a region of the Solar System, containing of mostly asteroids:

**Asteroids** except for the largest, Ceres, are classified as small Solar System bodies and are composed mainly of refractory rocky and metallic minerals, with some ice. They range from a few meters to hundreds of kilometers in size. Asteroids smaller than one meter are usually called meteoroids and micrometeoroids (grain-sized), depending on different, somewhat arbitrary definitions.

**The asteroid belt** occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU from the Sun. It is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter. The asteroid belt contains tens of thousands, possibly millions, of objects over one kilometre in diameter. Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth. The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident.

**Ceres** is the largest asteroid, and a dwarf planet. It has a diameter of slightly under 1000 km, and a mass large enough for its own gravity to pull it into a spherical shape. Ceres was considered a planet when it was discovered in 1801, and was reclassified to asteroid in the 1850s as further observations revealed additional asteroids. It was classified as a dwarf planet in 2006 when the definition of a planet was created.

## **Outer Solar System**

The Outer Solar System is a region of the Solar System that contains the 4 gas giants:

**Jupiter** is 2.5 times the mass of all the other planets put together. It is composed largely of hydrogen and helium. Jupiter's strong internal heat creates semi-permanent features in its atmosphere, such as cloud bands and the Great Red Spot. Jupiter has 79 known satellites. The four largest, Ganymede, Callisto, Io, and Europa, show similarities to the terrestrial planets, such as volcanism and internal heating. Ganymede, the largest satellite in the Solar System, is larger than Mercury.

**Saturn**, distinguished by its extensive ring system, has several similarities to Jupiter, such as its atmospheric composition and magnetosphere. Saturn is the only planet of the Solar System that is less dense than water. The rings of Saturn are made up of small ice and rock particles. Saturn has 82 confirmed satellites composed largely of ice. Two of these, Titan and Enceladus, show signs of geological activity. Titan, the second-largest moon in the Solar System, is larger than Mercury and the only satellite in the Solar System with a substantial atmosphere.

**Uranus**, is the lightest of the outer planets. Uniquely among the planets, it orbits the Sun on its side; its axial tilt is over ninety degrees to the ecliptic. It has a much colder core than the other giant planets and radiates very little heat into space. Uranus has 27 known satellites, the largest ones being Titania, Oberon, Umbriel, Ariel, and Miranda.

**Neptune**, though slightly smaller than Uranus, is more massive and hence more dense. It radiates more internal heat, but not as much as Jupiter or Saturn. Neptune has 14 known satellites. The largest, Triton, is geologically active, with geysers of liquid nitrogen. Triton is the only large satellite with a retrograde orbit.

## **Trans-Neptunian region**

The Trans-Neptunian region is a region within the Solar System that contains the Kuiper Belt and many dwarf planets:

**The Kuiper belt** is a great ring of debris similar to the asteroid belt, but consisting mainly of objects composed primarily of ice. It extends between 30 and 50 AU from the Sun. There are estimated to be over 100,000 Kuiper belt objects with a diameter greater than 15 km, but the total mass of the Kuiper belt is thought to be only a tenth or even a hundredth the mass of Earth. Many Kuiper belt objects have multiple satellites.

**Pluto**, a distant icy world smaller than the moon 40 AU from Sol. It has a shallow subsurface ocean under its ice crust, observed to be 14km deep, these depths host no life it in. It's orbit is so elliptical it switches places with neptune during its orbital period. It has a large moon named Charon, and they both orbit a barycenter.

**Haumea**, an egg shaped dwarf planet, one rotation on it takes only 4 hours. Making it the fastest spinning dwarf planet in the solar system. It has 2 moons called Namaka and Hi'aka. It also has a ring system making it the only kuiper belt object to have rings. It's surface is coated in ice with stone below it.

**Makemake**, a rocky dwarf planet far from sol, it's surface is covered with methane, ethane and a bit of nitrogen ice, it is rich in metallic ores like aluminum, copper and more. It has one small mining outpost on it called "Farout Mining Outpost".

**Eris**, an icy dwarf planet orbiting far beyond pluto and the other dwarf planets, with its one moon called Dysnomia. Not much is known about this icy world since it does not interest the space agencies