All About Our Planet Earth Essay
The Earth is a relatively small celestial object. It is the third planet orbiting an average star, our
Sun, located in the Orion arm, sometimes called the Orion Spur; it is a minor arm located in
between the Sagittarius Arm and the Perseus arm of the Milky Way, a barred spiral galaxy. Our
solar system orbits the central bulge of our galaxy at a radius of 1.7 billion AU and our period of
galactic revolution is 230 million years at a tangential velocity of 828,000 km/hr relative to the
center. Our solar system has one main sequence star, 4 inner rocky planets, the asteroid belt, 4 outer
large gaseous planets, the Kuiper Belt of small icy objects, and the outermost Oort Cloud of icy
objects made of water, ammonia, and methane. It extends from...show more content...
The supernova process generates elements more massive than iron, like the heavier elements we
find within our solar system, and ejects them. With a cloud of about 90% H, 9% He, and small
amounts of everything else, such as iron, carbon, and oxygen, and the movement of pressure waves
through the cloud due to the At the center of this contracting and rotating cloud, compressed H and
He gases formed a hot protostar. When temperature and pressure within the core of this protostar
increased to a critical point, a type of nuclear fusion, also called proton–proton fusion, began, and
thus our sun was born. At the same time, the remaining gas cloud that had enough inertia to avoid
being swept into the Sun collapsed into the form of a rotating sphere. According to the Condensation
theory, the first solid particles formed and then grew as they accreted the surrounding material. Soon,
these larger bodies, called planetesimals, had enough gravity to pull in more matter. The
planetesimals then collided to form the planets. The inner planets formed at temperatures high
enough that only heavier elements could form solids, so these planets are composed of rock and
metal. The lighter gaseous elements were swept outward by solarwinds. The Earth then began as an
accreting molten sphere. The Earth's thermal energy came from an initial stage of nuclear fission at
its center. Radioactive decay of
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