The Solar System is composed of a single G type star, being orbited by 9 major planets and 11 other dwarf planets. It is on the third planet that complex life began to evolve, and where Humanity as a species was born. The Sol System can only be accessed by Commanders once the Sol Permit has been granted to them.

Sol

Sol, or simply "the Sun", is the star at the center of the Solar System. Its spectral classification is G2 V, meaning it is a hot yellow-white star in the main sequence, currently fusing hydrogen into helium in its core. It is a variable star, its brightness fluctuating by 0.1% over the course of 11 years. Sol isn't as active as other stars in its class, which might have helped life to arise and flourish on Earth over billions of years.

Mercury

Mercury is the innermost of the major planets, and the smallest one. It completes one orbit in just under 88 days, and is tidally locked into a 3:2 spin-orbit resonance with Sol, rotating 3 times during every 2 orbits it completes. Its namesake comes from the Roman god Mercurius, messenger of the gods, for this planet moves the faster in Earth's sky than any other planet does. Since there is no substantial atmosphere here, Mercury experiences wild temperature shifts between its day and night side, the highest reaching 700 K (427 °C), while the lowest can be around 53 K (-220 °C).

Venus

Venus is the second innermost planet in the Solar System, and the hottest one. Its surface is obscured by a thick layer of sulfuric acid clouds, which are highly reflective, making it the brightest planet seen from Earth. This is why it was named after Venus, the Roman goddess of beauty and love. The planet has undergone a runaway greenhouse effect, trapping heat within its carbon dioxide-dominated atmosphere. As a result, temperatures around Venus are even hotter than Mercury's, with the average being a staggering 737 K (464 °C), with a surface pressure of 92 atm. Venus rotates backwards compared to the other planets, its rotation period being -243 days. This actually makes its rotation period longer than its sidereal orbital period, which is 224 days.

Earth

Earth is the third planet from Sol, and the largest of the terrestrial planets. Life began around 4 billion years ago here, evolving from simple self-replicating cells to complex intelligent life. Life on Earth changed the composition of Earth's atmosphere over time, producing substantial amounts of Oxygen through photosynthesis once cyanobacteria appeared, as well as Ozone. This, in tandem with the planet's strong magnetic field, protects its surface from harmful radiation from Sol and other cosmic sources. The first modern humans came about on the continent of Africa some 300,000 years ago, becoming the dominant species on the planet not long after. Humans further developed their societies through farms and towns to major cities and countries, eventually accomplishing space travel. Humans first set foot on the surface of another celestial body, the Moon, in 1969.

The Moon

The Moon (or less commonly "Luna") is Earth's sole natural satellite. It is theorised to have formed from a major planetary collision between Earth and a Mars-sized body named Theia. This event gave Earth its current axial tilt. Over time, the debris from the impact coalesced into a sphere and began to cool. Eventually, the Moon's volcanism stopped entirely. The vast lunar basalt plains called "seas" (mare) are evidence of this past volcanic activity.
The Moon is tidally locked to Earth, its rotational period being the same as its orbital period. This movement through the sky, visible as different "phases" from the Earth's surface, created what are now the months of the year, a month being about the same length as the Moon's orbital period.

The Moon is thought to be a major factor in the development of life on Earth, as its gravitational force caused tides on a rapidly-rotating Earth, pulling its liquid oceans back and forth and slowing its rotation. It also stabilizes the planet's axial tilt, giving the planet consistent seasons. Some life forms evolved to recognize and rely on the light of the Moon at night, such as newly hatched sea turtles, which use moonlight to find their way out to the ocean.

Mars

Mars is the fourth planet from Sol, and is the first ever planet to have been successfully terraformed, in 2291. Since early in the third millenium, Mars has been the capital of the Federation. In ancient times, this planet was particularly fascinating to humans because of its visually distinct red color in the sky. This is why it was named after Mars, the Roman god of war.
The planet has a similar axial tilt to Earth at 25.19°. Humans finally set foot here in the 2070s, and later on in the 2100s uncovered ancient fossils, providing clear evidence that life once existed there. The iron oxide left over from before terraforming began remains on the surface, still giving the planet a red hue from space.

Jupiter

Jupiter is the fifth planet from Sol and the largest in the system. It is a Class I Gas Giant and has more than twice the mass of all the other planets combined. From Earth, it is the third brightest natural object in the night sky, after the Moon and Venus. Its namesake is derived from the Roman god Jupiter, the king of the gods. Out of all the planets, Jupiter is believed to be the oldest, and is composed of 73.7% Hydrogen and 26.3% Helium. It rotates in 9 hours and 55 minutes, and this high rotational speed is what causes the planet's equatorial bulge. The planet's surface cloud layers have an abundance of stripes and storms, but the most notable of which is known as the "Great Red Spot", an enormous storm that has persisted since at least the year 1665.

The Galilean Moons

These 4 moons are known as the Galilean Moons after the astronomer who discovered them in the early 17th century, Galileo Galilei. These natural satellites were the first objects found to be orbiting a body other than the Earth. Their names come from the lovers of the Greek god Zeus, who is the equivalent to Jupiter. These moons are special in their own right: the third moon from Jupiter, Ganymede, is the largest moon in the Solar System, its diameter greater than that of Mercury, but not nearly as massive. Europa has a subsurface ocean caused by tidal heating between it and Jupiter. Io, Europa and Ganymede are locked in a 4:2:1 orbital resonance.

Galileo's discovery proved that the belief of his time that everything in the sky revolved around the Earth was false: everything revolved around the Sun instead. He also developed a method to determine a person's longitude on Earth based on the predicted timings of eclipses from the moons onto Jupiter. This was actually a precursor to proving that the speed of light is not infinite, but light does in fact take measurable time to travel to its destination. Earth's distance to Jupiter changes greatly over the course of its year, and as a result, the time it takes for light to travel from Jupiter to Earth is longer when they are on opposite sides of the Sun than it is when they are closer.

Saturn

Saturn is the sixth planet from Sol and is the second largest planet in the Sol system. The Class I Gas Giant is famous for its distinctive ring system that has been discernible through telescopes in ancient times. Its name comes from the Roman god of wealth and agriculture. The progenitor for these rings is unknown but it is thought that these rings are the result of a moon that was torn apart by tidal forces.

The Moons of Saturn

The Moons of Saturn are fascinating in appearance, as well as how they interact with one another along their orbits. The most popular of its moons are Enceladus and Titan. Titan was the first to be discovered by Christian Huygens in 1655, while Tethys, Rhea, Iapetus and Dione were discovered by Giovanni Domenico Cassini. Enceladus was discovered in 1789 by William Herschel.

Enceladus was the target of many scientific missions since the spacecraft Cassini studied it in close detail beginning in the 2000s. It is covered in fresh ice, as well as cratered regions, which distinctly separate younger and older regions. Major water vapor ejecta are shot from the moon's south pole regions and escape its surface gravity. Eventually these gases begin orbiting Saturn itself, creating Saturn's gaseous E ring.

Titan is significant amongst all the moons in the Sol System, as it is the only one discovered to have a thick atmosphere that is not just tenuous gases. It is mostly composed of Nitrogen with a small percentage of Methane. It is also the second largest natural satellite in the Sol System after Ganymede, and it too has a diameter greater than that of Mercury, but only 40% as massive. It is also the second body ever discovered after the Earth to have stable surface liquids, which are made up of liquid methane.

Iapetus has a visually striking surface, one hemisphere being much brighter than the other. These two hemispheres make the appearance from Earth change in apparent magnitude depending on what side is facing Earth as the moon orbits Saturn. As it is tidally locked, the two hemispheres consistently show up in the same places. This led to them being labeled as the bright hemisphere when the moon was to the west, and the dark hemisphere when the moon was to the east of Saturn. The discoverer, Cassini, correctly identified this being the case in the 1700s.

Uranus

Uranus is the seventh planet from Sol and the largest and least massive of the Ice Giants. Although actually visible with the naked eye in dark skies, ancient astronomers didn't recognize it as a planet, but instead thought it was a star, because of its slow orbit velocity, not making a noticeable change in position in the sky as much as the classical planets did. The English namesake for this planet and its moons are different than the other planets, as the planet's name Uranus is the Greek god of the sky, whereas the others are named after Roman gods. Uranus was discovered by William Herschel on the 13th of March, 1781. The planet has a significant obliquity, its tilt being 97.7° to its orbit. That means the planet, as well as the rest of the Uranian moon system, orbit near perpendicularly to its orbital plane. The planet also has a ring system, discovered on accident when the rings began to occult the star HD 128598, making the star disappear a few times before Uranus did.

Moons of Uranus

The moons of Uranus are named after the characters in the works of William Shakespeare and Alexander Pope. Herschel discovered Titania and Oberon six years after the discovery of Uranus, and in 1851 Ariel and Umbriel were discovered by William Lassell. Miranda was found in 1948 by Gerard Kuiper, and the other moons were discovered either by the flyby of Voyager 2 or other advanced Earth-based telescopes.

Neptune

Neptune is the eighth planet from Sol, and the smallest and most massive of the Ice Giants. The planet's namesake comes from Neptune, the Roman god of the sea. Unlike the planets inferior to it, Neptune is not visible to the naked eye and requires a telescope to see it. It is the first of two planets, besides Persephone, to be found using mathematical prediction instead of direct observation. It was found that the observed orbit of Uranus was not following the mathematically calculated orbit, leading Alexis Bouvard to hypothesize that there must be another planet beyond Uranus perturbing it. Urbain Le Verrier calculated where this hypothetical planet might be, and was eventually found within a degree of where Le Verrier predicted it was by Johann Galle. The planet has a very faint ring system, the first of which was discovered in 1968 by Edward Guinan.

Triton

Triton is a peculiar moon in the Sol System, as it orbits Neptune in retrograde, and is inclined 129° to the ecliptic. And yet, its eccentricity is 0.000016. It is thought to be a captured dwarf planet from the nearby Kuiper Belt. It is the seventh largest moon in the Sol System. For reasons unknown, the body is permit locked and no ships are currently allowed to land there.

Dwarf Planets

Pluto and Charon make up a double dwarf planet system in the Kuiper Belt. It was discovered by Clyde W. Tombaugh on February 18, 1930. At the time, astronomers insisted that Uranus' perturbed orbit could not be explained just by Neptune, so they kept searching for the so-called "Planet X". Tombaugh was using a blink comparator to search for small movements in certain night sky pictures when he found it.

In 2006, the International Astronomical Union declared an official definition for a planet, that the object must orbit the Sun, must have rounded itself into hydrostatic equilibrium, and cleared the neighborhood around its orbit. The last of the three Pluto did not do, and was therefore classified as a dwarf planet. The celestial body would not be visited until July of 2015, when the New Horizons spacecraft did a flyby, taking high-resolution pictures of Pluto and Charon.

The Pluto-Charon barycentre is in a 2:3 orbital resonance with Neptune. In fact, when viewing the entire solar system from above, Pluto's orbit appears to overtake Neptune's, being closer to the Sun than it. However, Pluto's orbit is inclined as such that the orbital path takes it 8 AU above Neptune's.

Persephone

Persephone is a dark and icy body nearly 10 times the mass of the Earth on a very long orbit around the Sun, taking 20,000 years to complete one orbit. It was first hypothesized to exist from apparent perturbations in the eccentric orbits of very distant Kuiper Belt objects. Throughout its search it was tagged as "Planet Nine". Astronomers correctly predicted that something was shepherding these bodies into peculiar orbits, for example the large perihelion of Sedna. It also explained why objects in near-perpendicular orbits have big semi-major axes. This is the second planet wherein its existence was discovered by orbital perturbation.

The Solar System is composed of a single G type star, being orbited by 9 major planets and 11 other dwarf planets. It is on the third planet that complex life began to evolve, and where Humanity as a species was born. The Sol System can only be accessed by Commanders once the Sol Permit has been granted to them.

Sol

Sol, or simply "the Sun", is the star at the center of the Solar System. Its spectral classification is G2 V, meaning it is a hot yellow-white star in the main sequence, currently fusing hydrogen into helium in its core. It is a variable star, its brightness fluctuating by 0.1% over the course of 11 years. Sol isn't as active as other stars in its class, which might have helped life to arise and flourish on Earth over billions of years.

Mercury

Mercury is the innermost of the major planets, and the smallest one. It completes one orbit in just under 88 days, and is tidally locked into a 3:2 spin-orbit resonance with Sol, rotating 3 times during every 2 orbits it completes. Its namesake comes from the Roman god Mercurius, messenger of the gods, for this planet moves the faster in Earth's sky than any other planet does. Since there is no substantial atmosphere here, Mercury experiences wild temperature shifts between its day and night side, the highest reaching 700 K (427 °C), while the lowest can be around 53 K (-220 °C).

Venus

Venus is the second innermost planet in the Solar System, and the hottest one. Its surface is obscured by a thick layer of sulfuric acid clouds, which are highly reflective, making it the brightest planet seen from Earth. This is why it was named after Venus, the Roman goddess of beauty and love. The planet has undergone a runaway greenhouse effect, trapping heat within its carbon dioxide-dominated atmosphere. As a result, temperatures around Venus are even hotter than Mercury's, with the average being a staggering 737 K (464 °C), with a surface pressure of 92 atm. Venus rotates backwards compared to the other planets, its rotation period being -243 days. This actually makes its rotation period longer than its sidereal orbital period, which is 224 days.

Earth

Earth is the third planet from Sol, and the largest of the terrestrial planets. Life began around 4 billion years ago here, evolving from simple self-replicating cells to complex intelligent life. Life on Earth changed the composition of Earth's atmosphere over time, producing substantial amounts of Oxygen through photosynthesis once cyanobacteria appeared, as well as Ozone. This, in tandem with the planet's strong magnetic field, protects its surface from harmful radiation from Sol and other cosmic sources. The first modern humans came about on the continent of Africa some 300,000 years ago, becoming the dominant species on the planet not long after. Humans further developed their societies through farms and towns to major cities and countries, eventually accomplishing space travel. Humans first set foot on the surface of another celestial body, the Moon, in 1969.

The Moon

The Moon (or less commonly "Luna") is Earth's sole natural satellite. It is theorised to have formed from a major planetary collision between Earth and a Mars-sized body named Theia. This event gave Earth its current axial tilt. Over time, the debris from the impact coalesced into a sphere and began to cool. Eventually, the Moon's volcanism stopped entirely. The vast lunar basalt plains called "seas" (mare) are evidence of this past volcanic activity.
The Moon is tidally locked to Earth, its rotational period being the same as its orbital period. This movement through the sky, visible as different "phases" from the Earth's surface, created what are now the months of the year, a month being about the same length as the Moon's orbital period.

The Moon is thought to be a major factor in the development of life on Earth, as its gravitational force caused tides on a rapidly-rotating Earth, pulling its liquid oceans back and forth and slowing its rotation. It also stabilizes the planet's axial tilt, giving the planet consistent seasons. Some life forms evolved to recognize and rely on the light of the Moon at night, such as newly hatched sea turtles, which use moonlight to find their way out to the ocean.

Mars

Mars is the fourth planet from Sol, and is the first ever planet to have been successfully terraformed, in 2291. Since early in the third millenium, Mars has been the capital of the Federation. In ancient times, this planet was particularly fascinating to humans because of its visually distinct red color in the sky. This is why it was named after Mars, the Roman god of war.
The planet has a similar axial tilt to Earth at 25.19°. Humans finally set foot here in the 2070s, and later on in the 2100s uncovered ancient fossils, providing clear evidence that life once existed there. The iron oxide left over from before terraforming began remains on the surface, still giving the planet a red hue from space.

Jupiter

Jupiter is the fifth planet from Sol and the largest in the system. It is a Class I Gas Giant and has more than twice the mass of all the other planets combined. From Earth, it is the third brightest natural object in the night sky, after the Moon and Venus. Its namesake is derived from the Roman god Jupiter, the king of the gods. Out of all the planets, Jupiter is believed to be the oldest, and is composed of 73.7% Hydrogen and 26.3% Helium. It rotates in 9 hours and 55 minutes, and this high rotational speed is what causes the planet's equatorial bulge. The planet's surface cloud layers have an abundance of stripes and storms, but the most notable of which is known as the "Great Red Spot", an enormous storm that has persisted since at least the year 1665.

The Galilean Moons

These 4 moons are known as the Galilean Moons after the astronomer who discovered them in the early 17th century, Galileo Galilei. These natural satellites were the first objects found to be orbiting a body other than the Earth. Their names come from the lovers of the Greek god Zeus, who is the equivalent to Jupiter. These moons are special in their own right: the third moon from Jupiter, Ganymede, is the largest moon in the Solar System, its diameter greater than that of Mercury, but not nearly as massive. Europa has a subsurface ocean caused by tidal heating between it and Jupiter. Io, Europa and Ganymede are locked in a 4:2:1 orbital resonance.

Galileo's discovery proved that the belief of his time that everything in the sky revolved around the Earth was false: everything revolved around the Sun instead. He also developed a method to determine a person's longitude on Earth based on the predicted timings of eclipses from the moons onto Jupiter. This was actually a precursor to proving that the speed of light is not infinite, but light does in fact take measurable time to travel to its destination.

Saturn

Saturn is the sixth planet from Sol, and the second largest planet in the Sol system. The Class I Gas Giant is famous for its distinctive ring system that has been discernible through even the earliest telescopes. Its namesake is the Roman god of wealth and agriculture. The progenitor for these rings is unknown, but it is thought that these rings are the remains of a moon that was torn apart by the giant's tidal forces.

The Moons of Saturn

The Moons of Saturn are fascinating in appearance, as well as in how they interact with one another along their orbits. The most well-known of these moons are Enceladus and Titan. Titan was the first to be discovered by Christian Huygens in 1655, while Tethys, Rhea, Iapetus and Dione were discovered by Giovanni Domenico Cassini, and Enceladus was discovered in 1789 by William Herschel.

Enceladus was the target of many scientific missions since the spacecraft Cassini studied it in close detail beginning in the 2000s. It is covered in fresh ice, as well as cratered regions, which distinctly separate younger and older regions. Major water vapor ejecta are shot from the moon's south polar regions, with enough velocity to escape the moon's surface gravity. Eventually these gases begin orbiting Saturn itself, forming Saturn's gaseous E ring.

Titan is significant amongst all the moons in the Sol System, as it is the only one discovered to have a thick atmosphere that is not just tenuous gases. It is mostly composed of Nitrogen, with a small percentage of Methane. Titan is also the second largest natural satellite in the Sol System after Ganymede, and it too has a diameter greater than that of Mercury. However, it is only 40% as massive as the planet. Titan is also the second body ever discovered after the Earth to have stable liquids on its surface, although it's not water: rather, at these cold temperatures (94 K), it is liquid methane instead.

Iapetus has a visually striking surface, with one hemisphere being much brighter than the other. These two hemispheres make the appearance from Earth change in apparent magnitude depending on what side is facing Earth as the moon orbits Saturn. As the moon is tidally locked, the two hemispheres consistently show up in the same places. This led to them being labeled as the bright hemisphere when the moon was to the West, and the dark hemisphere when the moon was to the East of Saturn. The discoverer, Cassini, correctly identified this in the 1700s.

Uranus

Uranus is the seventh planet from Sol, and the largest and least massive of the Ice Giants. Although it is actually visible with the naked eye in sufficiently dark skies, ancient astronomers didn't recognize it as a planet. They thought it was a star, because of its slow orbital velocity meant that the planet didn't travel visibly in the night sky as much as the classical planets did. (After all, the term likely comes from the Greek word planḗtai, which means wanderers, travellers.) The English namesake for this planet and its moons are different than the other planets, as the planet's name Uranus is the Greek god of the sky, whereas the others are named after Roman gods. Uranus was discovered by William Herschel on the 13th of March, 1781. The planet has a significant obliquity, its tilt being 97.7° to its orbit. That means the planet, as well as the rest of the Uranian moon system, rotate near perpendicularly to its orbital plane. The planet also has a ring system, a fact that was discovered on accident when the rings began to occult the star HD 128598, making the star disappear a few times before Uranus did.

Moons of Uranus

The moons of Uranus are named after the characters in the works of William Shakespeare and Alexander Pope. Herschel discovered Titania and Oberon six years after the discovery of Uranus, and in 1851 Ariel and Umbriel were discovered by William Lassell. Miranda was found in 1948 by Gerard Kuiper, and the other moons were discovered either by the flyby of Voyager 2, or through other advanced Earth-based telescopes.

Neptune

Neptune is the eighth planet from Sol, and the smallest and most massive of the Ice Giants. The planet's namesake comes from Neptune, the Roman god of the sea. Unlike the planets inferior to it, Neptune is not visible to the naked eye. It is the first of two planets, besides Persephone, to be found using mathematical prediction instead of direct observation. The observed orbit of Uranus did not follow its mathematically calculated orbit well enough, which led Alexis Bouvard to hypothesize that there must be another planet beyond Uranus that perturbs it. Urbain Le Verrier calculated where this hypothetical planet might be, and Johann Galle eventually found it within a degree of where Le Verrier predicted it would be. The planet has a very faint ring system, the first of which was discovered in 1968 by Edward Guinan.

Triton

Triton is a peculiar moon in the Sol System, as it orbits Neptune in retrograde, and is inclined 129° to the ecliptic. And yet, its eccentricity is 0.000016. It is thought to be a captured dwarf planet from the nearby Kuiper Belt. It is the seventh largest moon in the Sol System. For reasons unknown, the body is permit locked by the Pilot's Federation, and no ships are currently allowed to land there.

The Dwarf Planets

Pluto and Charon make up a double dwarf planet system in the Kuiper Belt. They were discovered by Clyde W. Tombaugh on February 18, 1930. At the time, astronomers insisted that Uranus' perturbed orbit could not be explained just by Neptune alone, so they kept searching for the so-called "Planet X". Tombaugh was using a blink comparator to search for small movements in certain night sky pictures when he found Pluto and Charon.

In 2006, the International Astronomical Union declared an official definition for a planet, that the object must orbit the Sun, must have rounded itself into hydrostatic equilibrium, and cleared the neighborhood around its orbit. The last of the three Pluto did not do, and was therefore classified as a dwarf planet. The celestial body would not be visited until July of 2015, when the New Horizons spacecraft did a flyby, taking high-resolution pictures of Pluto and Charon.

The Pluto-Charon barycentre is in a 2:3 orbital resonance with Neptune. In fact, when viewing the entire solar system from above, Pluto's orbit appears to overtake Neptune's, being closer to the Sun than it. However, Pluto's orbit is inclined as such that the orbital path takes it 8 AU above Neptune's.

Persephone

Persephone is a dark and icy body nearly 10 times the mass of the Earth on a very long orbit around the Sun, taking 20,000 years to complete one orbit. It was first hypothesized to exist from apparent perturbations in the eccentric orbits of very distant Kuiper Belt objects. Throughout its search it was tagged as "Planet Nine". Astronomers correctly predicted that something was shepherding these bodies into peculiar orbits, for example the large perihelion of Sedna. It also explained why objects in near-perpendicular orbits have big semi-major axes. This is the second planet wherein its existence was discovered by orbital perturbation.