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2. The Solar System The Solar Systemconsists of the Sun and its planetary system of eight planets, their moons, and other non-stellar objects. It formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. 3. For thousands of years, humans, with a few notable exceptions, did not recognize the existence of the Solar System. People believed the Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Although the Greek philosopher Aristarchus of Samos had speculated on a heliocentric reordering of the cosmos, Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric system. His 17th-century successors, Galileo Galilei, Johannes Kepler and Isaac Newton, developed an understanding of physics that led to the gradual acceptance of the idea that the Earth moves around the Sun and that the planets are governed by the same physical laws that governed the Earth. 4. PLUTO 5. . Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,684 km, about 109 times that of Earth, and its mass (about 21030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core.. The Sun's classification, is designated as a yellow dwarf, because its visible radiation is most intense in the yellow-green portion of the spectrum. 6. . 7. . Mercury Mercury is the innermost planet in the Solar System. It is also the smallest, and its orbit is the most eccentric (that is, the least perfectly circular) of the eight planets. It orbits the Sun once in about 88 Earth days, completing three rotations about its axis for every two orbits. The planet is named after the Roman god Mercury, the messenger to the gods. Mercury's surface is heavily cratered and similar in appearance to Earth's Moon, indicating that it has been geologically inactive for billions of years. Due to its near lack of an atmosphere to retain heat, Mercury's surface experiences the steepest temperature gradient of all the planets, ranging from a very cold 100 K at night to a very hot 700 K during the day. Mercury's axis has the smallest tilt of any of the Solar System's planets, but Mercury's orbital eccentricity is the largest. 8. . Parts of Mercury Internal structure of Mercury: 1. Crust: 100300 km thick 2. Mantle: 600 km thick 3. Core: 1,800 km radius 9. . VenusVenus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of 4.6. Its elongation reaches a maximum of 47.8. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it has been referred to by ancient cultures as the Morning Star or Evening Star. Venus is one of the four solar terrestrial planets The diameter of Venus is 12,092 km (only 650 km less than the Earth's) and its mass is 81.5% of the Earth's. Conditions on the Venusian surface differ radically from those on Earth, owing to its dense carbon dioxide atmosphere. The mass of the atmosphere of Venus is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen. 10. . Inside Venus 11. . Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the world, the Blue Planet, or by its Latin name, Terra. Earth Earth formed approximately 4.54 billion years ago, and life appeared on its surface within one billion years Earth's biosphere then significantly altered the atmospheric and other basic physical conditions, which enabled the proliferation of organisms as well as the formation of the ozone layer and permitted formerly ocean-confined life to move safely to land. The physical properties of the Earth have allowed life to persist 12. Inside Earth 13. . Mars 14. . Inside Mars 15. . Jupiter Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in the Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets. The planet was known by astronomers of ancient times, and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter Jupiter is composed primarily of gaseous and liquid matter. It is the largest of four gas giants as well as the largest planet in the Solar System with a diameter of 142,984 km. The density of Jupiter, 1.326 g/cm3, is the second highest of the gas giant planets. 16. . Inside Jupiter 17. . SaturnSaturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god Saturn, its astronomical symbol () represents the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth, While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive than Earth. Saturn is classified as a gas giant planet because the exterior is predominantly composed of gas and it lacks a definite surface, although it may have a solid core. The rotation of the planet causes it to take the shape of an oblate spheroid; that is, it is flattened at the poles and bulges at the equator. Its equatorial and polar radii differ by almost 10%60,268 km versus 54,364 km. 18. . 19. . 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 are of different chemical composition than the larger gas giants Jupiter and Saturn. For this reason, astronomers sometimes place them in a separate category called "ice giants". Uranus's atmosphere, while 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 hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (224 C). It has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane thought to make up the uppermost layer of clouds. In contrast, the interior of Uranus is mainly composed of ices and rock. Uranus 20. . Inside Uranus 21. . Neptune Neptune is the eighth and farthest planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Neptune is 17 times the mass of Earth and is somewhat more massive than its near- twin Uranus, which is 15 times the mass of Earth but not as dense. On average, Neptune orbits the Sun at a distance of 30.1 AU, approximately 30 times the EarthSun distance. Named for the Roman god of the sea, its astronomical symbol is , a stylised version of the god Neptune's trident. Neptune's atmosphere, while similar to Jupiter's and Saturn's in that it is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, contains a higher proportion of "ices" such as water, ammonia, and methane. 22. . Wait! Pluto is not a planet anymore! 23. According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit. Pluto has been demoted because it does not dominate its neighborhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons. In addition, bodies that dominate their neighborhoods, "sweep up" asteroids, comets, and other debris, clearing a path along their orbits. By contrast, Pluto's orbit is somewhat untidy. Originally classified as a planet, Pluto is now considered the largest member of a distinct population called the Kuiper belt. Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately a fifth the mass of the Earth's moon and a third its volume. It has a highly eccentric and highly inclined orbit. 24. . Inside Uranus 25. Inside UranusOTHER HEAVENLY BODIES 26. Comets A comet is an icy small Solar System body (SSSB) that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. Comets have been observed since ancient times. 27. Most Popular Comet Halley's Comet or Comet Halley , officially designated 1P/Halley, is the best- known of the short-period comets and is visible from Earth every 7576 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime. Other naked-eye comets may be brighter and more spectacular, but will appear only once in thousands of years. 28. Meteors A meteor is a bright streak of light in the sky (a "shooting star" or a "falling star") produced by the entry of a small meteoroid into the Earth's atmosphere. If you have a dark clear sky you will probably see a few per hour on an average night; during one of the annual meteor showers you may see as many as 100/hour. Very bright meteors are known as fireballs; if you see one please report it. 29. Most Popular Meteor Several "shooting stars" or meteors per hour can usually be seen on any given night. Sometimes the number of meteors seen increases dramatically: these are termed "meteor showers". In fact, some meteor showers occur annually or at rather regular intervals. The number is greater in autumn and winter. The number always increases after midnight and is usually greatest just before dawn. Perhaps the most famous are the Perseids which peak around August 12 every year. 30. Asteroid Asteroids are small Solar System bodies or dwarf planets that are not comets. The term asteroids historically referred to objects inside the orbit of Jupiter. They have also been called planetoids, especially the larger ones. These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disk of a planet and was not observed to have the characteristics of an active comet, but as small objects in the outer Solar System were discovered, their volatile- based surfaces were found to more closely resemble comets, and so were often distinguished from traditional asteroids. Thus the term asteroid has come increasingly to refer specifically to the small bodies of the inner Solar System within the orbit of Jupiter, which are usually rocky or metallic.. 31. Biggest Asteroid Vesta was first discovered on March 29, 1807 by Heinrich Wilhelm Olbers. The asteroid measures 578 km by 458 km and has a mass of 2.67 x 1020 kg. It has a magnitude of +5.4 to +8.5 and can be easily observed with binoculars on a clear night. It has been seen with the unaided eye on several occasions. Vesta rotates on its axis every 5.342 hours and has an axial tilt of 29. Temperatures on the surface range from a frigid -188C (85 K) to -18C (255 K). Hubble images have revealed ancient lava flows. This is a direct contradiction of the belief that asteroids are simple cold, dead rocks floating in space. There is a gigantic impact basin so deep that it exposes the asteroids mantle at the South pole. The mantle is thought to be 10 km below the asteroids surface. 32. Moon A natural satellite, moon, or secondary planet is a celestial body that orbits a planet or smaller body, which is called its primary. 33. Mercurys Moon 31 Crateris was once mistaken to be a moon of Mercury but it is in fact a star about 1750 light years away. Mercury does not have any moons. 34. Venus Moon Venus has no moons .. 35. Earths Moon Luna 36. Mars Moon Deimos Phobos 37. Jupiters Moons Metis Adrastea Amalthea Thebe Io Europa Ganymede Callisto Themisto Leda Himalia Lysithea Elara S/2000 J 11 Carpo S/2003 J 12 Euporie S/2003 J 3 S/2003 J 18 Thelxinoe Euanthe Helike Orthosie Iocaste S/2003 J 16 Ananke Praxidike Harpalyke Hermippe Thyone Mneme S/2003 J 17 Aitne Kale Taygete S/2003 J 19 Chaldene S/2003 J 15 S/2003 J 10 S/2003 J 23 Erinome Aoede Kallichore Kalyke Eurydome S/2003 J 14 Pasithee Cyllene Eukelade S/2003 J 4 Hegemone Arche Carme Isonoe S/2003 J 9 S/2003 J 5 Pasiphae Callirrhoe Sinope Sponde Autonoe Megaclite S/2003 J 2 38. Saturns Named Moons Pan Daphnis Atlas Prometheus Pandora Epimetheus Janus Mimas Methone Anthe Pallene Enceladus Tethys Telesto Calypso Dione Helene Polydeuces Rhea Titan Hyperion Lapetus Kiviuq Ijiraq Phoebe Paaliaq Skathi Albiorix Bebhionn Erriapo Skoll Siarnaq Tarqeq Greip Hyrrokkin Jarnsaxa Tarvos Mundilfari Bergelmir Narvi Suttungr Hati Farbauti Thrymr Aegir Bestla Fenrir Surtur Kari Ymir Loge Fornjot 39. Uranus Named Moons 40. Neptunes Moons Triton Nereid Naiad Thalassa Despina Larissa Proteus Galatea Plus five smaller, unnamed moons. Triton and Proteus orbit close to Neptune; Nereid is in a distant orbit. 41. 6 42. 10.