| Solar System Scratchpad|
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Solar System - Our home star system. Contains 4 terrestrial planets, 4 gas giant planets, several dwarf planets, an asteroid belt, and a kuiper belt, around a G-Class yellow dwarf star. Contains the only known habitable planet, Earth.
- Venus - The second planet from the sun and the hottest. The brightest object in the sky other than the sun and moon, it was once known as the evening and morning star. Has an atmosphere rich in Carbon Dioxide and a runaway greenhouse. Has extreme surface pressure, continent-sized highlands, and soft, gooey surface of melted rocks. Once thought to have had a global ocean that was lost. Most features volcanic in origin, entire surface periodically thought to erupt at once. Upper altitudes are thought to be favorable to life. Rains sulfuric acid. Visited by early Russian landers and orbiters. Orbited and mapped by Pioneer Venus and Magellan. Currently orbited by Venus Express.
- Earth - Third planet from the Sun and home planet of mankind. The largest solid body in the solar system. The only known planet to currently have abundant liquid water on its surface, oceans, and life. The only planet that has active plate tectonics and volcanism and the only one with a significant proportion of its own mass.
- Moon - The only natural satellite of the Earth. Its existence has affected life on Earth with its bright light and tidal effects. The closest relative mass for any satellite of a planet. One side faces the Earth, while the other always faces away. Has extensive volcanic past, negligible atmosphere. Presents an old cratered surface. Thought to have been formed when a planet-sized object struck the Earth. The only other body in the solar system that mankind has landed on. Currently orbited by the GRAIL satellites.
- Mars - The fourth planet orbiting the Sun. A red planet that is easily found in the night sky. It is considered to be composed of a single planetoid that did not grow due to further collisions with other planetoids due to disruptions by Jupiter. Most likely planet outside of the Earth to have once had liquid water and life and the most likely next destination for mankind. Had active volcanic and hydrological past. Has significant but thin atmosphere. Has two tiny moons which were probably captured. Has highest mountains and deepest valleys in Solar System due to its low gravity. Visited by more space probes, orbiters, landers, and rovers than any other planet. Currently being orbited by Mars Reconnaissance Orbiter and Mars Express and explored by Opportunity rover.
- Asteroid Belt
- Ceres - First body in the asteroid belt discovered, at first thought to be the eight planet, then redesignated the largest asteroid, and later a dwarf planet due to its roundness. It is the only dwarf planet in the asteroid belt. Composed mainly of water ice. Second destination for the Dawn spacecraft.
- Jupiter - The largest and earliest formed planet in the Solar System, contains over twice as much material as the rest of the solar system combined. Influenced the formation of the other bodies in the solar system greatly. Second brightest planet in the sky and named after the king of the gods. Has four large moons and dozens of smaller ones. Upper atmosphere composed of liquid hydrogen and helium, may have a small rocky core and no solid surface. Has banded cloud features and giant long lasting storms such as the Great Red Spot. Has a powerful magnetic field. Visited by many spacecraft, orbited by Galileo. Juno probe is en route to the planet.
- Saturn - Fifth planet from the Sun. The smaller of the two hydrogen/helium gas giants in the Solar System. Has large, bright, and complex ring system, which is visible in small telescopes. Has light tan banded surface, with occasional giant white storms, as well as a permanent octagon storm at the poles. Fastest spinning planet. Has one very large satellite, several smaller round ones, and dozens of irregular ones. Visited by Pioneer and Voyager spacecraft. Currently orbited by Cassini probe.
- Titan - Largest moon of Saturn and the only known moon to have a thick atmosphere. Only body known to have bodies of liquids on its surface other than the Earth, which are composed of hydrocarbons. Landed on by the Huygens probe and mapped by the Cassini orbiter.
- Kuiper Belt
- Pluto - Discovered after an extensive search for Planet X. Initially thought to be Earth size and dubbed the ninth planet, then continuously reduced in size as its brightness became clear and its large moon was discovered, until another object Eris was discovered in its region of space that was more massive than it, when it was demoted to a Dwarf Planet status. Considered by some a double dwarf planet due to its large moon. Also has three tiny moons and could support a ring system. First Kuiper Belt object discovered, in 2:3 orbital resonance with Neptune. Target of New Horizons spacecraft. Its surface may contain organics.
- Sagittarius A* System - Sagittarius A* is thought to be the Super Massive Black Hole (SMBH) at the center of our Milky Way galaxy and is 26,000 ly away. (The "*" in its name is pronounced "star" from the symbol, and not used to indicate that this object is a "star".) It forms one component of the larger Sagittarius A structure, a complex radio source that spans light years. The black hole is orbited by about a dozen stars, which tend to have comet-like orbits centered a couple thousand light years from the black hole. These stars orbit faster than any other found (only taking 10 to 100 years to complete their orbits). The orbits of the stars is used to determine that the black hole is 4.1 Million Solar Masses and occupies an area no more than 45 AU (about the size of Neptune's orbit). Streams of gasses also orbit the black hole, which may be the remnants of planets that started forming around its orbiting stars, but then got yanked from their stars when approaching too close to the black hole. The cloud G2 was expected to be destroyed when it approached its closest point to the black hole near its event horizon, but survived its journey unscathed. A magnetar (a type of neutron star with a powerful magnetic field) SGR J1745-2900 was recently discovered orbiting the black star. A possible Intermediate Mass Black Hole (IMBH) GCIRS 13E (1300 MS) orbits the SMBH further out at about 3 light years. This black hole itself has seven massive stars orbiting it. This object might have formed through the collision of several stars in an ancient globular cluster. About 10,000 black holes may orbit SGR A* within 70 light years, being kicked in towards the galactic center during encounters with smaller stars, which in turn get kicked out towards the galactic rim. The SMBH may devour these black holes at about a rate of 1 per million years. Gamma rays emitted by SGR A* caused X-Rays to be emitted from a giant molecular cloud Sagittarius B2 350 ly away. The event horizon is the target of the earth-spanning Event Horizon Telescope. It is thought that bursts by this black hole could strip away the atmospheres of neptune like planets so that they become super earths up to 70 light years away.
- TRAPPIST-1 System - A very old nearby ultra-cool dwarf star (not much larger than Jupiter) 39.13 ly away with seven transiting Earth-sized planets, more than any other system, and the first such planets around such a star. First planets found by the TRAnsiting Planets and PlanetesImals Small Telescope. The planets are very compact and the gravitational interactions are significant, with resonances linking all of them, making it possible to study their mass and densities. They're named in order of distance to star. When the innermost planet b completes 8 orbits, the next planets complete 5, 3, and 2 respectively. The outermost planet (h) was predicted to have a period in a certain resonance with the other outer planets, and this was confirmed. When h orbits twice, g orbits 3 times and f 4 times. Hubble confirmed that non of the HZ planets have extended Hydrogen atmospheres. At first, the innermost two are potentially habitable and represent the easiest to study planets for biosignatures to be detected, and the third was thought to be outside the habitable zone. The first two planets (b, c) are somewhat larger than the earth at the inner edge of the habitable zones (receive the amount of energy half-way between Mercury and Venus and Venus) and orbit at 1.5 and 2.4 days. The atmospheres of the inner planets are thought to have been destroyed by the stars intense solar wind withing millions of years. Planet b and c likely have molten rock mantles due to tidal stresses, while c likely has a rocky surface with Io-like tidally induced volcanoes and a largely rocky interior. The further out planets' atmospheres could have survived for billions of years though. The next two planets (d, e) are somewhat smaller than Earth and are a little more and a little less radiated than it in the middle of the HZ. Planet d (the smallest) likely has a global ocean, while e most likely has a largely rocky interior. Studies have shown that, depending on the composition and strength of the planet's own magnetic field, the star's magnetic field could cause induction heating to occur significantly in the middle planets. This could turn the surface into magma, or at least increase volcanic activity, raising the chances of a greenhouse. The next two planets (f, g) are somewhat larger than Earth and orbit in the outer habitable zone (at Mars like distances and at the outer edge). Planet f was at first thought to be the most habitable, but now next planet out g appears to be the most habitable. The view from the fifth planet would be remarkable, with the star appearing 10 times larger than the sun does in our sky, and the other planets appearing twice the size of the moon. Planet h is the only known planet outside the habitable zone and receives about the same irradiation as Ceres does, and yet still orbits six times closer than mercury does from the sun. There was a race among astronomers using kepler data to determine h's orbit. A study on potential cometary impacts found that the outer 3 planets could have had their original atmosphere's obliterated by the impacts, but that this would also supply new volatiles for a new atmosphere, including enough water for one earth ocean mass, suggesting they would have more massive atmospheres than the other planets.