Hubble images a part of the Universe

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Hubble images a part of the Universe
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In the beginning

• How did this all start?
• When did it start?
• Has it always been this way?
• How is it changing?
• What does it all mean?

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A Quest for Answers

• Observations of planets, stars, galaxies
• Analysis of light from stars and galaxies
• Thinking about these observations
• Posing an hypothesis
• Testing the hypothesis
• Evidence/tests either support or refute
  hypothesis
• Lets start with the observational evidence

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The Electromagnetic Spectrum

• Visible Light Range

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The Electromagnetic Spectrum
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Chemistry from Spectra

• Emission Spectra

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Chemistry from Spectra

• Absorption Spectra

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Analyzing Stellar Spectra

• Chemistry of Stars
• Predominantly Hydrogen (H)
• Second most common Helium (He)
• Other elements in minor quantities

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Analyzing Stellar Spectra

• Anomalies in positions of absorption bands
• Normal Spectrum

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Analyzing Stellar Spectra

• Anomalies in positions of absorption bands
• Shifted Spectrum

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Comparison of Normal and Shifted Spectra

• Normal Spectrum
• Shifted Spectrum

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What could cause shifted spectra?
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Animation

• http//lectureonline.cl.msu.edu/mmp/applist/doppl
  er/d.htm

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Doppler Effect

• Waves emitted from a moving source are shifted
  depending on direction of motion.
• Sources moving toward observer show shift toward
  shorter wavelengths (i.e., toward blue end of
  spectrum)
• Wavelength is compressed by motion of source.
• Referred to as BLUE SHIFT

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Doppler Effect

• Waves emitted from a moving source are shifted
  depending on direction of motion.
• Sources moving AWAY from observer show shift
  toward longer wavelengths (i.e., toward red end
  of spectrum)
• Wavelength is stretched by motion of source.
• Referred to as RED SHIFT

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Hubbles Law

• Nearly all galaxies in the Universe display RED
  SHIFT
• The amount of RED SHIFT is related to the
  relative distance to the galaxy.
• FARTHER galaxies show GREATER RED SHIFT

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Example of Red Shift

• Normal Spectrum
• Shifted Spectrum

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Hubbles Law What does it mean?

• Is the Earth the center of the Universe after all
  and everything is moving away from us?
• Does it depend on frame of reference?
• Would Hubbles Law apply if we looked at the
  Universe from another location?
• Why is everything moving away?

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Hubbles Observation/Hubbles Insight

• All galaxies appear to be moving away from the
  center of the Universe because the Universe is
  expanding.
• The existence of RED SHIFT and the pattern that
  it shows (greater shift for farther galaxies) is
  consistent with a pattern produced by an
  explosion
• THE BIG BANG!!

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The Big Bang

• Currently the best theory to explain the origin
  of the Universe
• Supported by multiple lines of evidence

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What was the Big Bang?

• Prior to the Big Bang there was no Universe
• A single super-massive object exploded
• Explosion creates Universe
• Matter, space and time are created
• Explosion was approximately 15 billion years ago

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• The Big Bang 10-35 seconds
• generates space time, as well as all the matter
  energy universe will ever hold
• For small fraction of a sec., the universe is an
  infinitely dense, hot fireball

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• The Universe Takes Shape -- 10-6 sec.
• universe continues to expand ? less dense
  cooler.
• now basic forces in nature become distinct
• Gravity strong force (holds nuclei of atoms
  together), followed by the weak electromagnetic
  forces.
• By end of 1st second, universe consists of
  particles energy -- smash together ? form
  protons neutrons.

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• Formation of Basic Elements -- 3 sec.
• nuclei of simple elements hydrogen, helium and
  lithium form
• (will be another 300,000 yrs before electrons are
  captured into orbits around these nuclei to form
  stable atoms).

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• The Radiation Era -- 10,000 years
• most of the energy left from the fireball is in
  the form of radiation --
• different wavelengths of light, X rays, radio
  waves ultraviolet rays

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• Birth of Stars Galaxies -- 300 my after BB
• (still 12 to 15 by before the present).
• pockets of gas become more and more dense as a
  result of gravitational attraction.
• Stars ignite within these pockets
• groups of stars become the earliest galaxies.

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• Birth of the Sun -- 5 Billion Years Before
  Present (BP)
• Sun forms w/in cloud of gas in spiral arm of
  Milky Way Galaxy.
• vast disk of gas debris swirls around new star
  ? gives birth to planets, moons, asteroids .

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Evidence in support ofBig Bang Theory

• Hubbles Law and pattern of red shift
• Cosmic Background Radiation
• Mathematical models
• Particle physics theory

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New Insights into the Big Bang

• Recent mapping of microwave and temperature
  variations suggest that the Universe may be flat
  not spherical!
• Implications?

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What about life elsewhere in the Universe and How
Big is the Universe?
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Spiral Galaxy
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Stars and Planets

• Each galaxy has about 100 billion stars
• There are billions of galaxies!
• Even if only 1 of stars had planets,
• And even if only 1 of those planets were like
  Earth,
• There would still be hundreds of millions of
  planets that could have life on them!

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How far are the stars? How big is the Universe?

• We can measure distances to stars by two methods
• One method parallax is only good for the very
  nearest stars
• The other method comparison of magnitudes is
  more complex, but it can be used for even the
  farthest stars and galaxies.

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Parallax

• Classroom demonstration of parallax
• Knowing one distance and one angle, we can
  calculate distance to star using trigonometry

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Apparent vs. Actual Stellar Magnitude (brightness)

• Compare how bright the star looks to how bright
  it would look at a known distance
• You must first know actual magnitude (brightness)

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How do we know actual magnitude?

• Cepheid variable stars absolute magnitude is
  directly related to period of pulsation
• Supernova fixed magnitude
• Spectral analysis gives composition, which is
  related to size, which is related to brightness

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How close is our nearest neighbor?

• Proxima centauri is 4.27 light years from Earth

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What is a light year?

• The distance that light will travel in one year.
• Since light travels at 186,000 miles per second,
• A light year is approximately 6 trillion miles

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Implications?

• Distances are enormous!!
• For some stars, it has taken the light billions
  of years to reach Earth
• In some cases, this means that the star isnt
  even there anymore!
• We see the light that left long ago, therefore

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Looking at the night sky is literally looking
into the past!!