The Origin of the Solar System (the Nebular Hypothesis)



The Formation of the Solar System

The Nebular Hypothesis

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Books make many statements as though they are facts, as opposed to theories

Much based on mathematical models which no normal mortal can hope to understand

The processes discussed happened a long time ago

These represent theories based on current levels of understanding

There are no direct methods to observe the formational process of the Solar System

All methods are essentially indirect and involve some major assumptions

So, let's keep the uncertainty factor in mind


The Formation of the Solar System

Any theory has to accounts for several observations

Dynamic constraints

Planets all move around sun in the same direction

All are on the Plane of the Ecliptic

Approx. in plane of the sun's own rotation

Most planets have same sense of rotation, as do their moons

Chemical constraints

Two basic types of planets

Separated by transitional asteroid belt

Inner planets are "rocky" (Mercury to Mars)

Outer planets are "gaseous"

Basically giant farts in space

Jupiter & Saturn are essentially small stars

Age constraints

Everything seems to have formed 4.5 billion years ago

This one is based on very limited work!


The Nebular Hypothesis

It is thought that the solar system formed by the condensation of a "nebula"

A nebula is a widely dispersed cloud of interstellar gas and dust

Slowly rotating in space and very cold (-270°C)

Gravitational attraction caused this matter to condense

Condensation resulted in faster rotation and an increase in temperature

Conservation of angular momentum

Collapse into a rotating disc of matter

Big bulge in the center with distended "arms" of matter

Led to the formation of the sun and planets

Most matter accumulated into the center to form the sun

At some point the amount of matter was sufficient to set off the nuclear reactions which cause stars to give off energy, but not right away

Proto-star: warmer than space but not hot enough to begin fusion

Fission vs. Fusion

Critical Mass

Anyway, "over the course of geologic time" enough matter came together to start the reaction

At the same time, planets were forming in the outer edges of the disc

The terms "accumulation, planetesimal, accretion" are used here

More on this later

But for now, the following is important

Jupiter also has a lot of matter: almost like a Proto-star

Does not have "Critical Mass" so no fusion reactions

The accumulation process is still going on

Earth intercepts 200,000,000 pieces of space debris daily!

Most are very small (dust), but there are still some large chunks out there

More on this later, too