This Set of Slides. This set of slides covers age and formation of solar system, exoplanets. Units covered: 33, 34. A number of naturally occurring atoms undergo radioactive decay. The atom splits apart into lower-mass atoms (fission.)
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A number of naturally occurring atoms undergo radioactive decay.
The atom splits apart into lower-mass atoms (fission.)
The time it takes for half of the atoms in a given sample to decay is called the material’s half-life.
After a number n of half-lives, the fraction of original material left is:
We can then use radioactive dating to tell how old a rock is.
The oldest rocks on Earth are around 4 billion years old.
Even older samples have been found on the Moon and in meteorites.
All bodies in the Solar System whose ages have so far been determined are consistent with having formed about 4.5 billion years ago.
The most successful model of Solar System formation is the Solar Nebula Theory:
The Solar System originated from a rotating, disk-shaped cloud of gas and dust, with the outer part of the disk becoming the planets, and the inner part becoming the Sun.
4.5 billion years ago, the immense cloud of gas and dust that would become our Solar System began to contract (due to gravity).
As it contracted, it flattened into a disk and began to spin faster (Conservation of Angular Momentum).
Most of the material in the cloud moved to the center to become the Sun.
In the inner solar system, silicate (rocky) and metal grains accreted (stuck together) over time, to form rocky planetesimals. These would become the terrestrial planets.
In the outer solar system, icy planetesimals formed.
These planetesimals collided and gathered mass over millions of years to form the planets
Planetesimals grew through accretion into protoplanets, which were heated by collisions and by radioactive decay.
Denser material sank toward the center of the bodies, and lighter material floated toward the surface.
This separation process is called differentiation.