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ORIGIN OF THE SOLAR SYSTEM Chapter 12 MAJOR PROPERTIES OF THE SOLAR SYSTEM Each planet is isolated about twice as far from the Sun as its inward neighbour. The orbit of each planet around the Sun is approximately circular. The planetary orbits lie nearly in the same plane. The direction of revolution of the planets around the Sun is the same as the Sun’s rotation. Most planets spin in the same direction except (V, U? and P). Most moons revolve in the same direction as the planets rotate. All of the above facts suggest a single formation event. MAJOR PROPERTIES OF THE SOLAR SYSTEM All of the above facts suggest a single formation event for the solar system. MAJOR PROPERTIES OF THE SOLAR SYSTEM Chemical The terrestrial planets are depleted in light elements such as H and He. Lighter elements were not able to condense (form solids) near the Sun. These elements escaped from the inner regions of the Solar System. MAJOR PROPERTIES OF THE SOLAR SYSTEM Ages Meteorites are 4.5 billion years old. MAJOR PROPERTIES OF THE SOLAR SYSTEM Ages Parts of the Moon are also 4.5 billion years old. MAJOR PROPERTIES OF THE SOLAR SYSTEM Ages Earth is at least 3.8 billion years old. FORMATION of the SOLAR SYSTEM The Solar System formed about 4.5 billion years ago from the solar nebula. New stars are currently forming in the Orion Nebula. Orion Nebula FORMATION of the SOLAR SYSTEM The Eagle Nebula is also a region of current star formation. Eagle Nebula FORMATION of the SOLAR SYSTEM Gravity pulls gas and dust to the centre of the nebula. Material spins faster as nebula shrinks. Easier for material to fall into the poles than equator. A disk is formed with most of the material collecting in the central region. The formation of a star FORMATION of the SOLAR SYSTEM Disks are observed around many young stars. When the supply of dust and gas is depleted, the collapse of the nebula ceases and the nebula then begins to cool. Protoplanetary Disks in the Orion Nebula FORMATION of the SOLAR SYSTEM As the nebula cools, the gas forms heavier compounds. Water is formed far from the centre. Its presence on Earth is unexpected. FORMATION of the SOLAR SYSTEM Grains aggregate together to form planetesimals (1 - 10 km, some still seen as asteroids and comets) Asteroid Ida Comet Hale-Bopp FORMATION of the SOLAR SYSTEM In the inner Solar System, planetesimals accreted to form the terrestrial planets. Era of heavy bombardment by planetesimals melted planets and caused differentiation. FORMATION of the SOLAR SYSTEM Primordial Earth glowed from impact generated heat. FORMATION of the SOLAR SYSTEM In the outer Solar System, lots of gas was available. Protopanetary cores accreted huge amounts of gas. Protoplanetary Cores FORMATION of the SOLAR SYSTEM The collapse of the solar nebula and the formation of the planets occurred in a few million years. FORMATION of the SOLAR SYSTEM The collapse of the solar nebula and the formation of the planets occurred in a few million years. Lots of planetesimals left in the inner solar system to cause havoc. Mercury Moon FORMATION of the SOLAR SYSTEM FORMATION of the SOLAR SYSTEM One or more large planetesimals collided with Venus and reversed its spin direction. Venus FORMATION of the SOLAR SYSTEM One or more planetesimals collided with Earth and pulled out enough material to form the Moon. FORMATION of the SOLAR SYSTEM Initially, the Earth had no water. Icy comets hitting Earth brought water and organic compounds from the outer region. Comet West SHOEMAKER-LEVI COMET FORMATION of the SOLAR SYSTEM Comets continue to impact the planets. Comet Shoemaker-Levi Impact Sites on Jupiter