Lecture 2 - Formation of the Solar System Flashcards
(49 cards)
When did the three major events in the universe happen?
The Big Bang happened 13.7 billion years ago.
The Milky Way formed 10-12 billion years ago.
The Solar System formed 4.6 billion years ago.
How was the Solar System formed?
A nearby star exploded which created a nebula.
The nebula collapsed under its gravitational attraction with the majority of the material forming the Sun.
The spinning gas that would form the Sun was surrounded by a nebula disk that eventually formed the planets.
What is a nebula?
A cloud of dust and gas.
What is a nebula disk?
A flattened disk of material.
What are the three stages of a planet’s growth?
Planetesimals
Proto-Planets
Planets
What are the steps for the formation of a planet?
1) The solar nebula contracts and flattens into a nebula disk.
2) The elements condense based on their volatility - less volatile elements (metals, rocks) condense in the inner solar system and more volatile elements (hydrogen, helium) condense in the outer solar system.
3) Solid particles stick together and eventually form a planetesimal.
4) Accretion of planetesimals occurs by them colliding - this forms proto-planets and then planets.
What are the features of the planets closer to the Sun?
Planets closer to the Sun have a greater density as they are composed of less volatile, heavier elements. Planets further away from the Sun have a much lower density as they are composed of volatile elements and ices.
Why does Mercury not have an atmosphere?
The gas molecules are too hot and have more energy than the gravitational pull present.
Why is Jupiter sometimes called a failed star?
It nearly had enough mass to generate a pressure and temperature high enough for nuclear fusion.
What characteristics of the Planets give clues to how they were formed?
They all orbit and rotate in the same direction and have volumes and masses that are predictable - supports planetary disk theory.
Their chemistries are different based on their distance from the sun and the volatility of the elements that formed them.
The texture and composition of meteorites gives information about the conditions in the solar system at its formation.
How is the Cosmic Abundance Graph and the composition of the Milky Way similar?
The abundance of the elements is the same.
What are the comparisons of Mercury and Jupiter?
Mercury is very dense, Jupiter is not very dense.
Jupiter is the largest planet in the solar system, Mercury is the smallest.
Mercury is much hotter than Jupiter.
Why are the Planets different sizes?
Due to the abundance of elements. Hydrogen, helium and ices are the most abundant and so form large planets in the outer solar system. Heavier elements are less abundant and so form smaller planets in the inner solar system.
Why do the Planets all orbit in the same plane and in the same direction?
They all formed in the same planetary disk.
What type of stars are nebula disks found around?
Young stars (<400 million years). This shows that accretion to form planetesimals occurs rapidly after star formation and ignition.
Why is the elemental abundance on Earth different to the Cosmic Abundance Graph?
It reflects the position of the Earth relative to the sun when the Earth was formed. This means that the Earth is formed of heavier, less volatile elements.
What is the elemental abundance on Earth centred on?
10⁶ atoms of Silicon.
What are the features of elemental abundance on Earth?
Oxygen is the most abundant element and elements become less abundant in a zig zag pattern.
What are the timescales for planetary accretion?
Planetary accretion happens within 400 million years after the formation of a solar system.
The Earth accreted within 100 million years of the formation of the Solar System.
What is the process of heterogenous accretion?
If segregation occurred during planetary accretion, the Earth would grow in layers and each layer would have a different chemical composition.
What is the process of homogenous accretion?
The Earth would be formed from a mixture of materials and there wouldn’t be any layers. The layering of the Earth would have had to have happened after accretion.
What is the process of heterogenous accretion in relation to the Earth?
1) The densest particles (richest in iron) would have accreted first and formed the core of the Earth.
2) Silicate materials would have accreted next.
3) The crust would have been formed from lighter elements delivered by meteorites called carbonaceous chondrites.
Which form of accretion is the most likely theory for the formation of Earth?
Homogenous accretion.
Although meteorites still could have hit the Earth afterwards which is heterogenous accretion.
What is the process of planetary segregation?
The Earth must have been hot enough to melt to segregate. Once melted, the denser elements would sink to the core and the less dense silicates would rise to the surface.
