Astronomy 100, Week 4.

  1. What happens when part of a nebulae begins to collapse?
    a. The temperature in center drops.
    b. The overall density goes down.
    c. The core pressure rises.
    d. The fusion of hydrogen into helium ceases.

  2. Why is our view of the Milky Way dark in some directions?
    a. Those areas are hidden by comets.
    b. Those areas are younger and thus have fewer stars born.
    c. Stars in some directions are mostly hidden by gas clouds.
    d. Stars in some directions are mostly hidden by dust clouds.

  3. What factor most determines the core temperature of stars?
    a. Volume
    b. Mass
    c. Radioactivity
    d. Velocity

  4. What is in nebulae that produces narrow absorption lines in the spectrum of light that passes through?
    a. large molecules
    b. gasses that are neutral or only partly ionized
    c. particles of dust
    d. gas that is completely ionized

  5. If a cloud was made of mostly helium instead of mostly hydrogen...
    a. Stars would form less often because the temperature required to fuse helium in the core is much higher than hydrogen.
    b. The time required for a star to reach final equilibrium would be shorter than if it was mostly hydrgen.
    c. The temperature of stars would be lower than the temperature in hydrogen stars.
    d. All of the above.

  6. What fuels the stars during most of their active lives?
    a. Exploding in supernovae events.
    b. Converting hydrogen into helium.
    c. Converting helium into carbon, nitrogen, and oxygen.
    d. Collapsing into protostars.

  7. What causes emission nebulae to mostly glow red and pink?
    a. Heat from nearby stars reflecting off dust grains.
    b. Nearby stars heating hydrogen gas clouds.
    c. Dust reflecting heat from supernovae.
    d. Cold hydrogen mixing with dust grains.

  8. What causes a reflection nebula to look blue?
    a. Hot stars penetrating interstellar gases.
    b. Hot stars close to interstellar dust clouds.
    c. Hot stars and Jupiter-like planets.
    d. Hot stars orbiting unseen companions.

  9. Which force of nature opposes the collapse of a brown dwarf?
    a. Heat from the collapse under gravity.
    b. Electron degeneracy pressure.
    c. Conversion of hydrogen into helium.
    d. Fusion of helium into carbon.

  10. Where do newly born t-tauri stars with the same mass as the sun get the additional energy to burn hundreds of times hotter than the sun?
    a. Electrical repulsion.
    b. Gravitational energy from the inward collapse.
    c. The proton-to-proton process.
    d. A powerful supernovae.

  11. What would happen if the Sun's core became hotter?
    a. pressure in the core would decrease.
    b. it would collapse.
    c. nuclear reactions would increase.
    d. the rotation would increase.

  12. What happens in a cloud made of only hydrogen and helium gas and no heavier elements?
    a. Mostly very massive stars would form because hydrogen and helium alone wouldn't cool the cloud the way heavy elements could.
    b. The overall temperature of cloud would be lower without heavy elements.
    c. Hydrogen molecules would form more readily and cool the cloud's temperature through radiation.
    d. Dust would hide the view and you could not observe the inner regions.

  13. Bok globules that are only one quarter the mass of our sun fail to become stars because...
    a.  the gravity involved is not enough for nuclear synthesis.
    b.  stars of the that size actually do form and many are even smaller.
    c.  the energy of the material cools too quickly.
    d.  the gravitational energy is too high.

  14. For what reason do astronomers think Vega is young?
    a.  It is very bright.
    b.  There is lots of dust around it which is typical of young stars.
    c.  It has very few heavy elements.
    d.  Radioactive dating indicates a young age.

  15. Where is a good place to look for complicated molecules?
    a. Dust clouds.
    b. Large stars.
    c. The sun.
    d. The halo of the galaxy.

  16. Why are there more low mass stars than high mass stars?
    a. High stars were born in the earlier universe.
    b. High mass stars live longer.
    c. Low mass stars dominate our neighborhood.
    d. Low mass stars require less mass to form which is quicker and easier.

  17. The space between the stars is dominated by these elements.
    a. Hydrogen and Helium.
    b. Iron and Nickel.
    c. Carbon, Nitrogen, Oxygen.
    d. Argon and Nitrogen

  18. Dust clouds in space have low density so why are they so effective at blocking light?
    a. The particles are shaped like little needles that line up along magnetic field lines.
    b. The particles are resonant with light because they are of similar size to the wavelengths.
    c. The dust surrounds stars.
    d. The particles are very large.

  19. In addition to the "atoms" what type of "molecule" appears most in nebulae?
    a. H2 (diatomic hydrogen)
    b. H2O (water)
    c. H2O2 (hydrogen peroxide)
    d. CO (carbon monoxide)

  20. Where do we get the evidence supporting our current theories regarding the formation of stars?
    a. From observing changes in the Sun.
    b. From observing changes in nebulae.
    c. From observing a very large number of stars and nebulae at all the phases of evolution.
    d. From observing changes in star properties over the past three hundred years.