Name: ______Date :______

Beyond Our Solar System(Chapter 24)

1)The Universe

______is the study of the universe, including its properties, structure and evolution.

  1. How Large Is It?
  2. The universe contains hundreds of billions of galaxies, each containing billions of stars.
  3. A Brief History of the Universe
  4. Big Bang Theory
  5. Model that most accurately describes the birth and current state of the universe.
  6. All of the energy and matter of the universe existed in an incredibly hot and dense state.
  7. About 13.7 billion years ago our universe began as a cataclysmic explosion, which continued to expand, ______, and evolve into its current state.

2)Interstellar Matter: Nursery of the Stars

As the universe ______, gravity caused matter to accumulate into large “clumps” and “strands” of interstellar matter known as nebulae. If a nebulae is dense enough it will contract due to gravity, leading to the processes that form stars and planets.

  1. Bright Nebulae – nebulae in close proximity to very hot (blue) stars, causing them to glow.
  2. ______Nebulae
  3. Glowing clouds of hydrogen gas in active star forming regions of galaxies.
  4. Light from young stars ionizes the hydrogen gas, causing it to emit visible light (red).
  5. ______Nebulae
  6. Composed of comparatively large debris, including carbon compounds.
  7. Reflects the light of nearby stars (blue).
  8. ______Nebulae
  9. Glowing clouds of dust and hot gases, originating from the remnants of dying stars.
  10. ______Nebulae – nebulae too far from bright stars to be illuminated.
  11. Consist of the same matter as bright nebulae.

3)Classifying Stars: Hertzsprung-Russell Diagrams

EinarHertzsprung and Henry Russell independently developed the information needed for a graph relating the true brightness of stars (luminosity) and their relative temperature.

  1. Hertzsprung-Russell Diagrams (H-R Diagrams) provide information about the relationships among the sizes, colors, temperatures of stars and stellar evolution.
  2. ______Stars
  3. Ninety percent (90%) of all stars.
  4. Red Giants and Super Giants
  5. Stars with large radiating surfaces.
  6. White Dwarfs

4)Stellar Evolution

The first stars probably formed about 300 million years after the Big Bang in the most massive nebulae and were very massive themselves. ______stars have relatively short lifetimes, followed by explosive deaths, expelling heavier elements out into space. The ejected matter is incorporated into future generations of stars.

  1. Stellar Birth
  2. Clouds of dust and gas begin to gravitationally contract, possibly due to shock waves from the collapse of nearby stars (______), pulling particles toward the center.
  3. The gravitational energy of the collapse is converted into kinetic and thermal energy, increasing the temperature until the gases radiate energy, becoming a protostar.
  4. ______Stage
  5. Gravitational contraction continues, slowly and then rapidly, causing the interior of the developing star to heat more quickly than the outer edge.
  6. When the core reaches a temperature of 10 million Kelvin hydrogen atoms will begin to fuse into ______, as hydrogen fusion.
  7. The internal outward pressure of the gases heated by fusion balances the inward directed force of gravity, creating a stable main sequence star.
  8. Main Sequence Stage
  9. Stars experience ______changes in size or energy output. Once the hydrogen fuel in the star’s core is depleted, the star evolves rapidly and dies.
  10. Red Giant Stage
  11. Usable ______in the star’s interior is used leaving a helium rich core, with hydrogen around the outside.
  12. No fusion takes place at the core and gravity collapses the core, but even greater hydrogen fusion begin at the surface, expanding the outer shell of the star.
  13. As the star expands the surface cools radiating at the red end of the spectrum.
  14. Burnout and ______
  15. Death of a Low Mass Star - stars less than one half the mass of the Sun consume their fuel at relatively low rates and can remain stable for 100 billion years, the collapse into a white dwarf.
  16. Death of a Medium Mass Star – Stars half to eight times the mass of the Sun, eject a cloud of gas as they collapse into a white dwarf, called a planetary nebulae.
  17. Death of Massive Stars -Stars more than eight times the mass of the Sun explode in a super nova, large energetic ejection of the outer layers of the star.

5)Stellar Remnants

Eventually all stars consume their nuclear fuel and collapse into one of three celestial objects – white dwarfs, neutron stars and black holes. Which final form it takes depends largely on the star’s ______.

  1. White Dwarfs
  2. Form from low and medium mass stars.
  3. Densities may be 1 million times the density of water.
  4. Atoms are squeezed together so tightly by gravity that electrons are pushed very close to the nucleus. Electrical repulsion between electrons prevents complete gravitational collapse.
  5. ______Stars
  6. Form from massive main sequence stars, remnants of explosive supernova events.
  7. Smaller and more ______than a white dwarf.
  8. Electrons are forced to combine with protons in the nucleus to produce neutrons.
  9. As the star collapses it begins to spin and radio waves begin to be emitted from the poles of the star. These stars that radiate short pulses of radio waves are called pulsars.
  10. ______
  11. Following a super nova, if the star’s mass exceeds ______solar masses, it collapses into an object denser than a neutron star.
  12. Their surface gravity is so immense even gravity cannot escape, causing black holes to disappear from sight. More dense than a neutron star
  13. As matter is pulled into it, it becomes very hot and emits X-rays.

6)Galaxies and Galactic Clusters

Galaxies are a collection of interstellar matter, stars and stellar remnants that are gravitationally bound. Super massive black holes may exist at the centers of most galaxies.

  1. Types of Galaxies
  2. ______Galaxies
  3. Arms extending from nucleus
  4. About 30 percent of all galaxies
  5. Large diameter up to 125,000 light years
  6. Contains both young and old stars
  7. e.g., Milky Way
  8. ______Spiral Galaxy
  9. Stars arranged in the shape of a bar
  10. Generally quite large
  11. About 10 percent of all galaxies
  12. ______Galaxies
  13. Ellipsoidal shape
  14. About 60 percent of all galaxies
  15. Most are smaller than spiral galaxies; however,

they are also the largest known galaxies

  1. Irregular Galaxies
  2. Lacks symmetry
  3. About 10 percent of all galaxies
  4. Contains mostly young stars
  5. Includes Magellanic Clouds
  1. Galactic Clusters
  2. Group of galaxies
  3. Some contain thousands of galaxies
  4. Local Group
  5. Our own group of galaxies
  6. Contains at least 28 galaxies
  7. Supercluster
  8. Huge swarm of galaxies
  9. May be the largest entity in the universe

7)The Big Bang Theory

  1. Evidence for an Expanding Universe
  2. Expanding Universe
  3. Slipher - Most galaxies exhibit a red Doppler shift
  4. Moving away
  5. Far galaxies have greatest shift
  6. Hubble’s Law – the recessional speed of galaxies is proportional to their ______.
  7. Predictions of the Big Bang Theory
  8. If the universe was initially unimaginably ______then researchers should be able to detect the remnants of that heat.
  9. The electromagnetic radiation of the hot universe would have high energy and short wavelengths, but the expansion would have stretched the waves. (CMBR)
  10. What is the Fate of the Universe?
  11. Two Possibilities
  12. Big ______– An endless, cold, dark universe where stars will burn out and be replaced by invisible degenerate matter and black holes.
  13. Big ______- Outward expansion will stop and gravitational contraction will follow, causing all matter to collide and coalesce into the high energy, high density state from which the universe began.
  14. Whether the universe will expand forever or eventually collapse on itself is dependent on density compared to critical density.
  15. If the average density is greater than the critical density gravitational attraction would be sufficient to stop outward expansion and cause the universe to collapse.
  16. If the average density is less than the critical density the universe will continue to expand forever.
  17. Dark Matter
  18. Everything we see accounts for less than 5 percent of the total mass of the universe. Dark matter is matter that does not interact with electromagnetic radiation
  19. Approximately one quarter of the universe consists of dark matter, which produces no detectable light energy but exerts a gravitational force that “pulls” on visible matter.
  20. Helps exert a force that helps hold our galaxy together and ______the expansion of the universe as a whole.
  21. Dark Energy
  22. Exerts a force that pushes matter outward, causing expansion to speed up.
  23. Believed to be dominant to dark matter, leading to increasing expansion.