nebular-theory-and-encounter-theory.pptx

Lesson 1.3 Nebular Theory and Encounter Theory  Learn about It! The Nebular Theory According to the nebular theory, the solar system originated from a nebula. It is the widely accepted view about the formation of the solar system some 4.5 billion years ago.  Learn about It! The Ne...

Lesson 1.3 Nebular Theory and Encounter Theory  Learn about It! The Nebular Theory According to the nebular theory, the solar system originated from a nebula. It is the widely accepted view about the formation of the solar system some 4.5 billion years ago.  Learn about It! The Nebular Theory A nebula is defined by NASA as giant cloud of gas and dust in space. This interstellar cloud of dust contains hydrogen, helium and other ionized gases. Dusty discs surrounding nearby young stars  Learn about It! Major Steps in the Formation of the Solar System The formation of the solar system from a nebula occurs in three major steps: (1) cloud collapse, (2) formation of protoplanetary disk, The Solar System and (3) growth of  Learn about It! Step 1: Cloud Collapse Hypothetically, a shockwave from a supernova or the effect of a passing star may cause a cloud collapse. The collapse at the center of the cloud due to gravity occurs when gas pressure becomes insufficient to support the mass of the cloud. The collapsed cloud of interstellar gas and dust results to a smaller radius that spins faster.  Learn about It! Collapsing of the cloud makes it spin faster. Cloud Collapse  Learn about It! Step 2: Formation of Protoplanetary Disk  Learn about It! Step 2: Formation of Protoplanetary Disk Metals and silicates could exist near the sun because these compounds have higher boiling points. As a result, terrestrial planets were Terrestrial planets. From left to right: Mercury, eventually formed Venus, Earth, and Mars; the last one on the right is Ceres, the terrestrial dwarf planet containing high concentration of these  Learn about It! Step 2: Formation of Protoplanetary Disk The terrestrial planets could not grow in huge diameter because of the limited reserve of metallic elements in the Terrestrial planets. From left to right: Mercury, solar nebula. Venus, Earth, and Mars; the last one on the right is Ceres, the terrestrial dwarf planet  Learn about It! Step 3: Growth of Planets Dust and grains surrounding the sun eventually formed clumps. These clumps then accreted forming planetesimals. Planetesimal is a small celestial body that once collide together. It tend to fuse to form the planets of the solar system.  Learn about It! Step 3: Growth of Planets Growth of planets in the nebular theory.  Learn about It! Proponents of the Nebular Theory Emmanuel Immanuel Pierre-Simon Swedenborg Kant Laplace (1688–1772) (1724–1804) (1749–1827)  Learn about It! Drawbacks of the Nebular Theory Particles surrounding Saturn repel each other, which is contrary to the assumption that dust particles will be attached to each other forming a planet. It does not follow the law of angular momentum because if the nebular theory is correct then the sun should be spinning at a higher rate than the others.  Learn about It! The Encounter Theory The encounter theory proposes that the planets were formed from the material ejected from the sun during an encounter with another celestial object, such as another star. An artistic visualization Two forms: planetesimal of the encounter theory and tidal theories  Learn about It! Planetesimal Theory It proposes that a passing star termed as intruding star nearly collided with the protosun. The massive gravitational pull of the intruding star causes the protosun to eject filaments of material which then condensed into planetesimals. This theory describes how Earth started from a solid mass smaller than its present size.  Learn about It! Proponents of the Planetesimal Theory Thomas Chrowder Chamberlin proposed that accretion of minute solid particles created planets and their moons rather than by gaseous or liquid material condensation. Thomas Chrowder Forest Ray Chamberlin Moulton  Learn about It! Proponents of the Planetesimal Theory Forest Ray Moulton provided the mathematical calculations to Chamberlin’s idea. Thomas Chrowder Forest Ray Chamberlin Moulton  Learn about It! The Tidal Theory It explains that the solar system formed as a result of a near collision between a passing star and the sun. This theory proposes that the hot gas from the passing star condensed into planets instead The lengthy tidal tails of the of condensing into colliding antennae galaxies planetesimals.  Learn about It! Proponents of the Tidal Theory The tidal theory was proposed by: ○ James Jeans, an English physicist and astronomer, and ○ Harold Jeffreys, an English mathematician and astronomer in 1918. Sir James Jeans  Key Points Nebular theory proposes that stars originate from interstellar gas and dust called nebula (cloud) and is credited to Swedenborg, Kant, and Laplace. Three major steps in nebular theory include ○ Cloud Collapse: The origin of the planets and sun in the solar system is a huge cloud of molecular gas and dust that collapsed. ○ Formation of the Protoplanetary Disk: Materials from the collapsed cloud fall inward and flatten into a disk. ○ Growth of Planets: Dust and grains surrounding the disk collide and form planetesimals that collect into a planet.  Key Points Encounter theory proposes that the planets formed from the material ejected from the sun during an encounter with another celestial object. Planetesimal theory is a form of encounter theory that describes Earth started from a solid mass smaller than its present size proposed by Chamberlin and Moulton. Tidal theory is a form of encounter theory which states the hot gas from the passing star condensed into planets instead of condensing into planetesimals proposed by Jeans and Jeffreys.