Nebular and Encounter theory

Nebula

-According to the nebular theory, the solar system originated dorm a _______.
-It is the widely accepted view about the formation of the solar system some 4.5 billion years ago.

Nebula

-giant cloud of gas and dust in space.
-contains hydrogen, helium, and ionized gases.

1. Cloud collapse
2. Formation of protoplanetary disk
3. Growth of planets

Major steps in the formation of the solar system (nebular theory):

Cloud collapse

-A shockwave from a supernova or the effect of a passing star may cause a ________.
-Results to a smaller radius that spins faster.

Formation of protoplanetary disk

-Metals and sillicates could exist near the sun because theses compounds have higher boiling points.
-As a result, terrestrial planets were eventually formed containing high concentration of these compounds.
-The terrestrial planet could not grow in huge diameter because of the limited reserve of metallic elements in the solar nebula.

Metals and sillicates

-Could exist near the sun because theses compounds have higher boiling points.

limited reserve of metallic elements

-The terrestrial planet could not grow in huge diameter because of the ________ in the solar nebula.

Growth of planets

-Dust and grains surrounding the sun eventually formed clumps. these clumps then accreted forming planetesimals.
-Planetesimals is a small celestial body that once collide together. (It tend to fuse to form the planets of the solar system.)

Planetesimals

-is a small celestial body that once collide together.

Emmanuel Swedenborg
Immanuel Kant
Pierre-Simon Laplace

Proponents of the nebular Theory:

-Particles surrounding the 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 the angular momentum because if the nebular theory is correct then the sun should be spinning at a higher rate than the others.
-It did not consider Uranus and Venus which rotates in a clockwise direction while other planets rotates in a counterclockwise direction.

Drawbacks of the Nebular 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.

Planetesimal
Tidal Theories

Two forms of encounter theory:

Planetesimal Theory

-it proposes that a passing star termed as intruding star nearly collided with the protosun.

Planetesimal Theory

-The massive gravitational pull of the intruding star causes the protosun to eject filaments of material which then condensed into planetesimals.

Planetesimal Theory

-This theory describes how Earth started from a solid mass smaller than its present size.

Thomas Chrowder Chamberlin
Forest Ray Moulton

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.

Forest Ray Moulton

-Provided the mathematical calculations to Chamberlin’s idea.

-No longer accepted today due to the fact that hot material from the sun expands and dissipates rather than contract.
-In addition, the force from the passing star will pull dust and gases far away from the sun, that they would not be able to form the planets in the solar system.

Drawbacks of the Planetesimal Theory:

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 of condensing into planetesimals.

James Jeans
Harold Jeffreys

Proponents of the Tidal Theory:

James Jeans

-An English Physicist and astronomer

Harold Jeffreys

-English mathematician and astronomer.

-Hot material from either star cannot contract.

Drawbacks of the Tidal theory: