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Solar System 1. Sun The Sun is the star at the center of the Solar System and is by far the most important source of energy for life on Earth. It is a nearly perfect spherical ball of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. Its diameter is about 109 times that of Earth, and it has a mass about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quartersof the Suns's mass consists of hydrogen;the rest is mostly helium ,with much smaller quantities of heavier elements, including oxygen , carbon , neon and iron. The Sun is a G-type main -sequence star based on spectral class and it is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became increasingly hot and dense , eventually initiating nuclear fusion in its core. It is tought that almost all stars from by this process. The Sun lies close to the inner rim of the Milky Way's Orion Arm, in the Local Interstellar Cloud of the Gould Belt, at a distance of 25.000-28.000 light-years from the Galactic Center. The Sun is contained within the LOcal Bubble , a space of rarefied hot gas, possibly produced by the supernova remnant Geminga. The distance between the local arm ad the nest arm out, the Perseus Arm is about 6.500 light-years. 1.000.000-2.000.000 K. The temperature of the photosphere is approximately 6.000K , whereas the temperature of the corona reaches The brightness of the Sun can cause pain from looking at it with the naked eye, however, doing so for brief periods is not hazardous for normal non-dilated eyes. Looking directly at the Sun causes phosphene visual artifacts and temporary partial blindness. But, without the Sun, we won't exist. 2. Mercury Mercury is the smallest and closest to the Sun of the eight planets in the Solar System, with an orbital period of about 88Earth days. Seen from Earth, it appears to move around its orbit in about 116 days, which is much faster than any other planet in the Solar System. It has no known natural satellites. The planet is named after the Roman deity Mercury, the messenger to the gods.Because it has almost no atmosphere to retain heat, Mercury's surface experiences the greatest temperature variation of the planets in the Solar System, ranging from 100 K (−173 °C; −280 °F) at night to 700 K (427 °C; 800 °F) during the day at some equatorial regions. The poles are constantly below 180 K (−93 °C; −136 °F). Mercury's axis has the smallest tilt of any of the Solar System's planets (about 1 ⁄30 of a degree), but it has the largest orbital eccentricity. At aphelion, Mercury is about 1.5 times as far from the Sun as it is at perihelion. Mercury's surface is heavily cratered and similar in appearance to the Moon, indicating that it has been geologically inactive for billions of years. 3. Venus Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.It has no natural satellite. It is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching anapparent magnitude of −4.6, bright enough to cast shadows.] Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°.Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, mass, proximity to the Sun and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of 735 K (462 °C; 863 °F), Venus is by far the hottest planet in the Solar System, even though Mercury is closer to the Sun. 4. Earth Earth Earth (also the world, in Greek: Γαῖα Gaia, or in Latin: Terra) is the third planet from the Sun, the densest planet in the Solar System,the largest of the Solar System's four terrestrial planets, and the only astronomical object known to harbor life. The earliest life on Earth arose at least 3.5 billion years ago. Earlier physical evidences of life include graphite, a biogenic substance, in 3.7 billion-year-old metasedimentary rocks discovered in southwestern Greenland, as well as, "remains of biotic life" found in 4.1 billion-year-old rocks in Western Australia. Earth's biodiversity has expanded continually except when interrupted by mass extinctions.Although scholars estimate that over 99 percent of all species of life (over five billion) that ever lived on Earth areextinct, there are still an estimated 10–14 million extant species, of which about 1.2 million have been documented and over 86 percent have not yet been described.Over 7.3 billion humans live on Earth and depend on its biosphere and minerals for their survival. Earth's human population is divided among about two hundred sovereign states which interact through diplomacy, conflict, travel, trade and communication media. 5. Moon The Moon is Earth's only natural satellite. It is one of the largest natural satellites in the Solar System, and, among planetary satellites, the largest relative to the size of the planet it orbits (its primary). It is the seconddensest satellite among those whose densities are known (after Jupiter's satellite Io). The Moon is thought to have formed approximately 4.5 billion years ago, not long after Earth. There are several hypotheses for its origin; the most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia. 6. Mars Mars is the fourth planet from the Sun and the second smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often referred to as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympu Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan. 7. Asteroid Belt The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids.About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea.The total mass of the asteroid belt is approximately 4% that of the Moon, which is significantly less than that of Pluto and roughly twice that of Pluto's moon Charon (whose diameter is 1200 km). 8. Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter is a gas giant, along with Saturn. (Uranus and Neptune are ice giants.) Jupiter was known to astronomers of ancient times. The Romans named it after their god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus. 9. Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. Although only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive. Saturn is named after the Roman god of agriculture; its astronomical symbol(♄) represents the god's sickle. 10. Uranus Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus's atmosphere, although similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, contains more "ices", such as water,ammonia, and methane, along with traces of other hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224.2 °C), and has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock. 11. Neptune Neptune is the eighth and farthest known planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Among the giant planets in the Solar System, Neptune is the most dense. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50×109 km). Named after the Roman god of the sea, its astronomical symbol is ♆, a stylised version of the god Neptune's trident. 12. Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuipe belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered. It is the largest and second-most-massive known dwarf planet in the Solar System and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris, a dwarf planet in the scattered disc. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of Earth's Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU (4.4–7.4 billion km) from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding. Light from the Sun takes about 5.5 hours to reach Pluto at its average distance (39.5 AU).