Formation of Solar System Chapter 27 Planets of the Solar System Austin HS – Earth and Space 2016

Formation of the Solar System The solar system consists of the sun and all of the planets and other bodies that revolve around the sun Planets are any of the primary bodies that orbit the sun In the 1600s and 1700s, it was thought that the sun formed first and threw off the materials that later formed the planets In1796, Pierre-Simon de Laplace, advanced a hypothesis that is now known as the nebular hypothesis

The Nebular Hypothesis Laplace’s hypothesis states that the sun and planets condensed at about the same time our of a rotating cloud of gas and dust. Matter gathered into cloud of dust and gas, the amount of gravity near one of these cloud increased as a result of a nearby supernova or other forces The rotating cloud of dust and gas from which the sun and planets formed is called a solar nebula. Energy from collision and pressure from gravity caused the center of the solar nebula to become hotter and denser. When temp. became high enough- hydrogen fusion began A star called the sun formed The sun is composed of about 99% of all the matter that was contained in the solar nebula

Formation of Planets While sun formed in the center of the solar nebula, planets forming in the outer region Planetesimals, are the small bodies from which a planet originated in the early stages of formation of the solar system Planetesimals joined together through collision and force of gravity to form large bodies called protoplanets Protoplanet’s gravity attracted other planetesimals in the solar nebula, eventually they became very large and condensed The formed planets and moons Moons are smaller bodies that orbit the planets

Formation of the Inner Planets Features of a newly formed planet depends on the distance between protoplanet and developing sun Protoplanets closet to the sun (Mercury, Venus, Earth, Mars) contained large % of heavy elements such as iron (Fe) and Nickel (Ni) they lost less dense gases because at the temp of the gases, gravity was not strong enough to hold Lighter elements may have been blown away or boiled away by radiation The denser material sank to the center, layers formed Inner planets have solid surfaces similar to earth, they are smaller rockier, and denser then outer planets

Formation of the Outer Planets The next 4 planets (Jupiter, Saturn, Uranus, Neptune) are very different from inner planets Outer planets formed in the colder regions of the solar nebula far from the sun Thus they did not lose their lighter elements such as helium and hydrogen/ or their ices (water ice, methane ice, ammonia ice) @ 1st thick layers of ice surrounded small heavy elements, due to heat and pressure in planets interior, ice melted to form layers of liquid and gases Planets are referred to as gas giants because they are composed mostly of gases, have low density, and are huge planets Jupiter’s density is only 24% of that of earth’s density. Jupiter has a diameter 11 times larger than Earth’s diameter.

The Different Planet - Pluto Pluto farthest planet from the sun Pluto is very small unlike other outer planets Pluto is very cold, may be described as an ice ball that is made of frozen gases and rock Astronomers have also discovered hundreds of objects that are similar to Pluto and that exist beyond Neptune’s orbit None are larger than Pluto Many scientist think that Pluto does not qualify as a major planet

Work on The Nebular Model of the Formation of the solar system. The End Work on The Nebular Model of the Formation of the solar system.