http://www.wimp.com/bigbang/

Ever ask yourself the question…

How did this all begin?

Gravity is what is responsible for the formation of our Universe• Universe Galaxies Solar System

Earth

Our Galaxy The Milky Way

Our Solar System

Relative Sizes of the Planets to the Sun109 EARTHS FIT ACROSS THE DIAMETER OF THE SUN

Stellar Evolution of Sun- Stellar Evolution of Sun- what is what is the fate of our sun?the fate of our sun?

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How do stars evolve and what determines how they die? THEIR INITIAL MASS!!!!!!

How does a star form?• All stars are made up of predominantly

Hydrogen and Helium

• Protostar Protostar • clump of interstellar material; a star in its clump of interstellar material; a star in its

infancy/conception stagesinfancy/conception stages

• formed from dark nebulae (clouds of dust that are formed from dark nebulae (clouds of dust that are so opaque that they block all visible light)so opaque that they block all visible light)

• Two forces need to act on the interstellar Two forces need to act on the interstellar material to condense and form a material to condense and form a starstar1.1. Force of gravity Force of gravity – pulls the interstellar materials together– pulls the interstellar materials together

2.2. Internal Pressure Internal Pressure – pushes the material apart (the materials – pushes the material apart (the materials become so tightly packed that they begin repelling each become so tightly packed that they begin repelling each other)other)

Formation of Stars:Formation of Stars:STAGE 1STAGE 1

How do stars shine? Nuclear fusion!!!!!!!

• Hydrogen fusion happens in the very core of all MS stars

• It combines particles into bigger particles

• This process releases HUGE quantities of energy

Hydrogen Fusion

Hydrogen

Hydrogen

Hydrogen

Hydrogen

Nuclear Fission Nuclear Fusion

DefinitionFission is the splitting of a large atom into two or more smaller ones.

Fusion is the fusing of two or more lighter atoms into a larger one.

Natural occurrence of the process

Fission reaction does not normally occur in nature.(but used in nuclear bombs)

Fusion occurs in stars, such as the sun.

ConditionsCritical mass of the substance and high-speed neutrons are required.

High density, high temperature environment is required.

Energy Released

The energy released by fission is a million times greater than that released in chemical reactions, but lower than the energy released by nuclear fusion.

The energy released by fusion is three to four times greater than the energy released by fission.

Both give off huge amounts of energy!

The Main Sequence• As the protostar compresses,

it forms a dense core

• Once it is hot enough, Hydrogen fusion starts

• A star enters the “Main Sequence” (MS) when Hydrogen fusion begins

• The MS is the longest stage of a star’s life – 90% of all stars are in this

stage

During the MS

• A star is in “equilibrium”

• It’s size stays constant – compression from

gravity = the outward pressure from the gas

DURING THE MAIN SEQUENCE

Increasing Temperature

HR DiagramHR DiagramBRIGH

T

DIM

COOLHOT

Hertzsprung- Russell Diagram• is an important chart that displays how the temperature

and luminosity of a star can be represented. There are a few general points to note (and can be seen from the diagram)

• Bluer stars are hotter and redder stars are cooler (just like the hottest part of a flame is the blue part).

• The more massive a star is the hotter it is (so the bluer it appears) and the more luminous (the more light it gives off).

• Once nuclear fusion begins a star is ‘born’ it enters the Main Sequence phase of its life. A star spends 90% of its life on the main sequence.

• Once stars have used up their hydrogen, once they stop fusing hydrogen, they are no longer classified as a main sequence star.

What about the Big Bang?

What about Universal Expansion?

http://www.teachersdomain.org/resource/phy03.sci.phys.fund.hubble2/

Different elements emit different wavelengths of light

So light tells us about composition- what the star is made of

The Doppler Effect

Objects moving AWAY FROM EACH OTHER experience RED SHIFT

Objects moving TOWARDS EACH OTHER experience BLUE SHIFT

The Doppler Effect –

indicates if a star is moving towards us or away from us.

Moving away from us!

Moving toward us!

What the line emission spectrum tells us- what light tells us

SUMMARY• (1.) Composition- what the star is made

of – which elements

• (2.) Movement- we see a redshift of the spectral lines if the star is moving away and a blue shift if the star is moving towards us

Hubble’s Law: The farther the galaxy, the faster it is moving away from Earth. (distance from and speed moving away from are directly proportional)

Edwin Hubble

Revolutionized our view of the universe.

Hubble- Summary- why is he important?

• 1st: He made us realize ours was not the only galaxy

• 2nd: He made us realize the universe is much much larger than people had previously believed

• 3rd: His data showed that all galaxies are accelerating away from us!

The Big Bang Theoryhttp://www.imdb.com/video/cbs/vi1889142553/

Big Bang• What is the Big Bang and what is our evidence

for it?

The Big Bang is Cosmological theory explaining the development of the universe. 13.7 billion years ago the universe began as a hot, dense, tiny ball of pure energy (singularity)– Space-time was created, began expanding outward– Cooled while expanding

• Subatomic particle creation

– Eventually, gas and dust combined to form planets and stars

• Heavier elements formed in the core of evolving stars

Image constructed from Wilkinson Microwave Anisotropy Probe (WMAP)

… evidence for Big Bang

• CMBR has been redshifted due to expansion all the way to radio end of the spectrum.

• WMAP is a map of all CMBR we are receiving. We are receiving it from all directions uniformly, so if you ‘press rewind’ this would indicate that at one time all of this light came from same place

3 pieces of evidence for the Big Bang

(1.) CMBR- left over light from the Big Bang

(2.) Hubbles law- the fact that the universe is expanding tells us it was once much smaller

(3.) The abundance of H and He observed today matches the predictions of this theory