Origins of the Universe

What you need to know about life, the universe, and everything………

Origins of the Universe

• Where did it all begin?• Almost every civilization has some theory of the origin of the universe.

• Science relies on only the testable evidence for theories.

Nicholas Copernicus 1473 - 1543

• Renaissance mathematician and astronomer

• Was the first person to suggest that the Earth was not the center of the universe

• Formed the heliocentric model of the universe which placed the Sun, rather than the Earth, at the center

Johannes Kepler1571 - 1630

• 17th Century mathematician, astronomer and astrologer

• Best known for his three laws of planetary motion– Explains the movement of the planets as part of his theory of the universe

Georges Lemaître1894 - 1966

• Considered the father of the Big Bang Theory• Was a Belgian cosmologist and Catholic priest.

• First written in a scientific paper in 1931.

Big Bang Theory

• Theory that suggests the Universe was created when the point of singularity (smaller than an atom) violently expanded blasting matter into celestial bodies

• Three primary evidences support the big bang theory: - background radiation has been found throughout the universe, - the red shift - scientists have not found a star older than the approximate age of the Universe

• Scientists predict the Universe will expand forever

Big Bang Evidence #1Background Radiation

• Background radiation has been found throughout the universe •Afterglow of the big bang – different from star-generated radiation•Can be seen at different wavelengths of the electromagnetic spectrum

Big Bang Evidence #2The Red Shift and Blue

Shift

• A red shift is seen when light coming from an object is moving away from another object

• A blue shift is seen when the light coming from an object is moving towards another object.

• Most celestial bodies in the universe show a red shift suggesting all objects are moving away from each other à supports the big bang theory that the universe is expanding and will expand forever

• The FREQUENCY of light is what allows it to have a red or blue shift

• Distant galaxies are moving away from Earth faster than galaxies that are nearby

Big Bang Evidence #3The Age of the Known Stars

• Scientists have not found a star older than the approximate age of the Universe• Indicates that all matter began at the same time

Speed of Light• The speed of light is 299, 792,458 METERS PER SECOND

• This means that light could travel from San Francisco to New York 62 times in ONE SECOND

•All light travels at around• 300,000 km/sec

Light Year (ly)

• The distance light travels in one year

•The next closest star to our Sun is 4.3 ly away and is named Proxima Centuri

• What are the limitiations (problems) with this model of the Earth, Sun, and Proxima Centuri?

Star Life Cycle (the good times)

• Nebula - clouds of gas and dust drawn together by gravity

• Protostar – gravity pulls matter together but not yet begun fusion• Brown dwarf – never reaches fusion (Star)

• Main Sequence – once Hydrogen fusion begins releasing energy (where visible stars spend most of their life)

Star Life Cycle (The end)

• Red Giant / Red Supergiant (large mass) - Runs out of Hydrogen, begins fusing Helium. Increased temperatures expand outer shell. • When all Hydrogen is fused, makes heavier

elements by fusing lighter ones together, until iron.

• Even heavier elements only made during Novas/Supernovas

• Depending on mass, its center will collapse and either become: a White Dwarf (low mass) or • Supernova that will become a Neutron star (large mass) may be a Pulsar

• Supernova that will become a Black Hole (very large mass)

Star Life Cycle (The end)

• Once all fusible material is used, the stars will burn out and become a black dwarf – a dead star.

• No known examples exist. This is because the universe is not old enough to have any stars this advanced.

Apparent Magnitude• A measure of how bright a star is when seen from Earth

• Stars may appear bright because they either produce a lot of light OR they are very close to Earth. There is no way to tell if the start is bright because it is close or because it is actually a bright star without more data.

• Apparent Magnitude= How bright does the star APPEAR???

Absolute Magnitude• A measurement of the amount of light the star give off

• This is more accurate than apparent magnitude.

• Our Star (the Sun) is average in size, average in magnitude and is considered “middle age” star or about 5 billion years old in a 10 billion year lifespan and is considered a Main Sequence Star

Hertzsprung-Russell Diagram (HR Diagram)

How to read an HR Diagram

• A scatter plot of star temperature (x-axis) and luminosity (y-axis)

• Temperature of star is measure in Kelvins

• Luminosity is measure in Solar Units

• Use it for categorizing star age• Important Difference than regular scatter plots and HR Diagrams: Read the X-Axis from Right to Left

Galaxy Shapes• Spiral

• Elliptical

• Irregular

• The Milky Way is a spiral galaxy and Earth is located in one of the spiral arms near the edge of the galaxy