View from the top of the Flatirons (Boulder, CO)

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AZ NM

You do not need to know the details of this slide

The universe began with the “Big Bang” 13-15 billion years ago.REVIEW

As the universe expanded after the Big Bang, it began to cool down.

Once it cooled down enough, matter could form into atoms.

Most of these atoms were hydrogen.

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Hydrogen – 1 proton and 1 electron

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Gravity caused the hydrogen to attract to each other, collecting into clumps of gas called nebulae. This process still occurs today.

Nebula: a cloud of gas and dust in space.

The Eagle Nebula, photographed by the Hubble Telescope.This image was created by ASU astronomers, Jeff Hester and Paul Scowen.

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In some regions of a nebula, the hydrogen is clumped together tight enough to form what is called a “protostar”.

Protostar – a large object that forms by the contraction of gas within a nebula

As the protostar grows, temperature and pressure increase.

If the temperature and pressure get high enough, the protostar will ignite by “fusion”.

Fusion – the process by which atomic nuclei join together to form a heavier element.

Hydrogen + Hydrogen = Helium + a lot of energy

A helium atom weighs less than 2 hydrogens

During fusion, mass turns into energy.

E = MC2 (Energy = the mass difference times the speed of light, squared)

In other words, a very small amount of mass turns into a LOT of energy!

2 Hydrogens fusing to form 1 helium + 1 neutron + a lot of energy.

Hubble photograph of stars formed in a nebula named the “Large Magellanic Cloud”. There are so many stars formed in this nebula that astronomers often call it a “stellar nursery”.

As a star runs out of hydrogen to fuse, larger elements will start fusing.

Fusion can create heavier and heavier elements, all of the way up to iron (Fe).

An example of how a large star can have different fusion layers.

You don’t need to know the details of this figure.

Eventually, the star will run out of elements to fuse.

Once a large star runs out of nuclear material, it will implode and then explode as a “supernova”

Supernova – a stellar explosion

As the star explodes, the energy isso great that new elements thatare heavier than iron can form.

Almost all of the elements heavierthan hydrogen are formed byfusion and supernova explosions.This is called “nucleosynthesis”.

Nucleosynthesis – the process ofcreating new atomic nuclei frompre-existing ones.

After a supernova, all of these new elements are disbursed into space, forming a new nebula.

Nebula formed by a supernova explosion

Our solar system likely formed out of a nebula created by a supernova explosion.

The hypothesis that explains the formation of our solar system is called the “nebular hypothesis”.

Nebular Hypothesis

1. Our solar system originated as a nebula containing mostly hydrogen and helium, with a small amount of heavier elements.

2. As the nebula contracted, it formed a protostar at its center.

3. Also, as it contracted, it began to rotate faster and it flattened into a disk. This is because of the “conservation of angular momentum”.

4. The protostar ignited by fusion.

5. The rest of the disk formed into planets by gravitational attraction.

A protoplanetary disk in the Orion Nebula.

Nebular hypothesis

Particles of matter become clumped together( this is called “accretion”)

Small grains boulders planetesimals planets

•The Inner (terrestrial) and outer (giant, Jovian) planets developed in different ways.

UE4EUE4E Figure 1.3 Figure 1.3

Inner versus outer planets

UE4EUE4E Figure 1.4 Figure 1.4

Cosmic rays from the sun swept most gases to cooler, outer part of the disk

The outer planets are made of ice that surrounds their rocky cores

They are massive enough such that their gravity can hold on to thick atmospheres.

They are formed mostly of rock and metal (solid at high temperature)

Inner PlanetsOuter Planets

UE4EUE4E Figure 1.4 Figure 1.4

Know the names and order of the planets. You will be asked this on an exam!

1. Mercury2. Venus3. Earth4. Mars5. Jupiter6. Saturn7. Uranus8. Neptune9. Pluto (no longer considered a planet)

Terrestrial planets

Jovian planets, also called gas-giants

The early solar system was full of many asteroids made of rock and metal.

The Earth was formed a little over 4.5 billion years ago by the “accretion” of this rock and metal.

As the Earth grew larger, it gained more gravity. This attracted even more matter to it!

The early Earth was like a gravitational vacuum cleaner, sweeping up the asteroids along its orbital path around the sun.

It is hypothesized that early on (~4.5 billion years ago) a large planetoid about the size as Mars hit the Earth. This is called the “giant impact hypothesis”.

This collision caused the formation of the Moon and the tilt of the Earth’s rotational axis.

Earth Heats Up

As the Earth formed, it heated up.

Why did it heat up? 2 Main reasons:

1. Many meteorite impacts - kinetic energy of the meteorites converted to heat energy upon impact.

kinetic energy - the energy of a moving object

Kinetic energy = ½ mass * velocity2 (note the square)

2. Radioactive decay of elements in rock. The primary radioactive elements in rock are uranium, thorium, potassium.

Earth Differentiates

Lightest rock: Lightest rock: crustcrust

Denser rock: Denser rock: mantlemantle

Iron and otherIron and otherheavy heavy elements: elements: corecore

As the Earth become very hot, it began to “differentiate”.

Differentiation: The transformation of random chunks of primordial matter into a body whose interior is divided into layers of different density.

(you don’t need to know these numbers)

The Earth differentiated into 3 layers: core, mantle, and crust.

UE4EUE4E Figure 1.7 Figure 1.7

Whole Earth:

1) Iron2) Oxygen3) Silicon

Crust (composed of the lighter elements):

1) Oxygen2) Silicon3) Aluminum

Know these 3 most abundant elements in the whole Earth and in the crust!

Oxygen + Silicon = Rock

Meteorites

Stony-iron meteorites (likely from a partially differentiated asteroid)

Building blocks of the Earth

Iron and some nickel

Rock (mostly olivine)

NASANASA

granite continental crust

Dense rock mantle(olivine)

Dense iron core(and some nickel)

meteorite basalt oceanic crust

The ocean and early atmosphere probably formed from volcanoes.

The Theory of PLATE TECTONICSThe Theory of PLATE TECTONICS

13 Major Tectonic Plates