This theory was proposed by Kant and Laplace. According
to this theory, the Sun and all the planets of our Solar System began as a
giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, a
passing star, or shock waves from a supernova caused gravitational collapse at
the center of the cloud.
From this collapse, dust and gas began to
collect into denser regions. As the denser regions pulled in more and more
matter, conservation of momentum caused it to begin rotating, while due to increasing
pressure it heated up. Most of the material came at the center as a ball, while
the rest of the matter flattened out into disk that circled around it. While
the ball at the center formed the Sun, the rest of the material formed
the protoplanetary
disc.
The planets within a critical distance, where
temperature was warmer, were rocky (terrestial), while those beyond the
critical distance had solid cores and thick, gaseous atmospheres (jovian).
At the border of the solar system, where
gravitational forces were weak, the icy bodies walked in eccentric orbits and
formed asteroids, and when they get close to the sun, they formed comets.
Eventually, the Sun became a main-sequence
star. Solar wind from the Sun created the heliosphere and swept away the remaining gas and dust from the
protoplanetary disc into interstellar space.
solar nebular
cloud collapse
pancake
planet building
Difference
between a nebula and galaxy
Nebula is a
cloud of interstellar dust and other ionized gasses particularly helium and
hydrogen. A galaxy on the other hand is a huge collection of stars
that are held together by gravitational attraction. A galaxy contains star systems,
star clusters along with interstellar dust.
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