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Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth (10 5 to 10 7 molecules per cubic centimeter) – a nebular cloud the size of the Earth would have a total mass of only a few kilograms.
The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets.
In cosmogony, the nebular hypothesis is the most widely accepted model explaining the formation and evolution of the Solar System. It was first proposed in 1734 by Emanuel Swedenborg . Originally applied only to our own Solar System , this method of planetary system formation is now thought to be at work throughout the universe .
The first planetary nebula discovered (though not yet termed as such) was the Dumbbell Nebula in the constellation of Vulpecula.It was observed by Charles Messier on July 12, 1764 and listed as M27 in his catalogue of nebulous objects. [10]
The nebular hypothesis says that the Solar System formed from the gravitational collapse of a fragment of a giant molecular cloud, [9] most likely at the edge of a Wolf-Rayet bubble. [10] The cloud was about 20 parsecs (65 light years) across, [9] while the fragments were roughly 1 parsec (three and a quarter light-years) across. [11]
The history of scientific thought about the formation and evolution of the Solar System began with the Copernican Revolution. The first recorded use of the term " Solar System " dates from 1704. [ 1 ] [ 2 ] Since the seventeenth century, philosophers and scientists have been forming hypotheses concerning the origins of the Solar System and the ...
1602-1608 – Galileo Galilei experiments with pendulum motion and inclined planes; deduces his law of free fall; and discovers that projectiles travel along parabolic trajectories. [3] 1609 – Johannes Kepler announces his first two laws of planetary motion. [4] 1610 – Johannes Kepler states the dark night paradox. [5]
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution