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Formation of the Planets

formation of the planets the universe

comprises countless galaxies each one

containing numerous stars around some of

those stars there are planets just like

those that orbit our own star the Sun

the nebular hypothesis is the most

widely accepted explanation for how the

Sun and planets in the solar system may

have formed when our solar system was

first created all that was thought to

have existed was a cold spinning cloud

of gas called the solar nebula the

nebula resulted from an uneven

distribution of gases throughout the

universe as the gravitational pull began

to condense the gas toward the center

the speed of the rotation increased

this caused the cloud to flatten

creating an accretion disk matter

continued to collect as the growing

force of gravity drew it toward the

center eventually the gas warmed from

the increasing pressure as the mass

further increased the gravity also

increased and as a result the

temperature continued to rise a ball of

hot gas formed in the center of the

accretion disk creating a protostar also

known as the Sun finally when enough gas

gathered in the center of the protostar

the pressure generated enough heat to

fuse the atoms forming a star outside

the star matter was forming into clumps

of gas dust and rock which created proto

planets these protoplanets continued to

grow as they trapped material in their

gravitational fields

because the proto planets all formed

from the same cloud of gas and dust they

travel around the Sun in the same

direction and in the same plane the

nebular hypothesis also explains how the

planets are arranged the heat and solar

winds caused by the Sun swept the

lighter gases farther out into the

developing solar system this is why the

rocky terrestrial planets Mercury Venus

Earth and Mars are located closer to the

Sun the gas giants Jupiter Saturn Uranus

and Neptune formed in the cooler outer

region of the solar system the solar

system continued to evolve even after

its initial formation large asteroids

slammed into planets and the planets

themselves differentiated into layers as

they slowly cooled

although the nebular hypothesis cannot

be directly tested it is a useful

description for how a solar system forms

it explains why planets and the star

they orbit usually spin in the same

direction and lie in the same plane it

also explains the arrangement of the

planets with the rocky planets nearest

to the Sun and the gas giants farther

away the next time that you look at the

stars twinkling in the night sky imagine

new planets forming using these very

steps

you

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