The Universe
SCI 210
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I. The History of the Universe
A. The Big Bang: 12-14 billion years ago
1. Accounts for galaxies moving away from us.
2. Before the Big Bang, the universe was small, incredibly dense
and hot
3. Big Bang marks the beginning of the Universe (including time!)
4. Matter is moving outward from the site of the BB
B. Galaxies formed as pockets of gas began to clump together
C. Within these galaxies, smaller pockets of gas began to form into
stars and solar systems\
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II.
How Do We Know What We Know?
A. How
far away are stars?
1. Stellar parallax
2. Distances are so large that we use
"light years" (9.5 trillion km or 5.8 trillion miles)
B. How
are stars moving with respect to us?
1. Doppler
effect: an apparent change in wavelength of light emitted by an object due
to its motion
a.
Motion away stretches the wavelength,
light
appears redder
b.
Movement toward compresses the wavelength,
light
appears bluer
2. Most galaxies have Doppler shifts to the Red end of the
spectrum (called "Red Shift") indicating that they are moving away
from us
3. The best explanation for this is the
"expanding universe" theory, which led scientists to the Big Bang
Theory for the evolution of the universe.
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III. Where We Live in Space: Earth: Solar System: Milky Way: Local
Group: Universe
A. Solar system located in the Milky Way Galaxy: a spiral galaxy
B. Galaxies are clumps of stars. They can be aligned (spiral,
barred spiral, elliptical and irregular)
C. Galaxies can be clumped into galactic clusters: ours is the
"Local group"
D. Most stars are main sequence stars.
1. These have a whole range of sizes and temperatures
2. "Live fast, die young" largest, hottest stars have
the shortest lifespan
E. Stellar evolution
1. Stars exist because of gravity
2. Two opposing forces:
a. Gravity contracts material
b. Thermal nuclear energy expands the
material
1. Nuclear fusion
2. Hydrogen fuses into Helium
plus energy
3. Star Life Cycle
a. Birth of a star: interstellar gas cloud
b. Protostar formed when gravity collapses gases in, temp.
rises, fusion begins
c. Main sequence stars: 90% of star's life. Length varies
for each star. Fusion continues
d. Star death: fuel (hydrogen) used up
1. Low-mass stars expand into red giants, then collapse to
white dwarfs
2. Medium-mass stars (like our Sun) expand into Red
Giants, then collapse into white dwarfs
3. Massive stars become Red
Supergiants, Supernovas, then
Neutron stars or Black holes. Supernovas create more
complex elements.
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IV. Early History of Our Solar System
A. The Sun (our star) is a second-generation star because our solar
system has material that was created during a supernova (death of an earlier star)
B. Early History
1. Our solar system formed about 4.5-4.6 billion years ago
2. Dating the solar system (and our Earth)
a. Moon rocks dated at4.5-4.6 b.y.a. age
b. Meteorites dated at 4.5-4.6 b.y.a.
3. Material collapsed into the star (our Sun) and the 9 planets
4. Earth's early history:
a. Collisions of planetesimals with Earth converts energy to
heat.
b. Temp. reaches melting point of iron producing Iron
Catastrophe/Crisis (dense materials sink, light materials rise
which creates differentiation or separation of Earth into layers)
c. No atmosphere on early Earth or else it was lost
d. Origin of the atmosphere: Volcanic out-gassing and maybe
contributions by extra-terrestrials (comets! Not spacemen)
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V. Our Solar System
A. The Sun: an average star, one of 200 billion in the Milky Way
1. Has layers: solar interior, photosphere, chromosphere, corona
2. Solar features. Two examples: sunspots, solar flares
B. The terrestrial planets
1. Mercury, Venus, Earth, Mars
2. Relatively small, dense, rocky
3. Planetary structures: rocky mantles, iron-nickel core, some
have a molten outer core and a magnetic field
4. Some are heavily cratered: Mercury, Mars, our Moon
5. Some are tectonically active: Earth, Venus
6. Venus has a runaway greenhouse atmosphere
7. Others (Mars, Mercury) have little or no atmosphere
8. Earth is the "just right" planet
C. Asteroid belt between Mars and Jupiter
1. Small, irregular, with eccentric orbits
2. Asteroids have impacted with the Earth, moon and other planets
D. The Jovian Planets (Gas Giants)
1. Jupiter, Saturn, Uranus, Neptune
2. Huge, low density, gaseous, maybe have a rocky core
3.Thick atmospheres: hydrogen, helium, methane, ammonia
E. Pluto - doesn't fit into either group of planets
F. Other parts of our solar system
1. Comets: "dirty snowballs"
a. Composed of frozen gases and rocky and metallic materials
b. Gases vaporize when near the sun, produces a coma (glowing
head) and sometimes a tail
2. Planetary satellites
a. Almost all planets have at least one
b. Our moon:
1. Relatively large, much less dense than Earth
2. No atmosphere: surface cratered
3. Tectonically dead
3. Meteoroids
a. Called meteors in Earth's atmosphere, meteorite when found on
surface of the Earth
b. There are different types of meteorites
c. Some are debris left from a comet's path
d. Iron-nickel meteorites may give an idea of the comp. of the
Earth's core.
e. Dating of meteorites gives an idea of the age of the solar
system
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