Why are there no black dwarfs yet, but in the future they may make up the majority of normal matter in the universe?
What will be an ideal response?
White dwarfs cool off slowly, so the oldest one in the galaxy is still probably hotter than our Sun. Since low mass stars seem to dominate in number high mass stars, as they become white dwarfs, they will eventually cool off to form black dwarfs if the universe lasts long enough.
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In Part A, you found that Planet Z should not have seasons. What single change to Planet Z's characteristics would cause it to have seasons?
a. a larger axis tilt b. a smaller size= c. a faster rotation rate d. a greater distance from its star
According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?
A) The force of gravity pulled the material downward into a flat disk. B) The law of conservation of energy C) It was fairly flat to begin with, and retained this flat shape as it collapsed. D) It flattened as a natural consequence of collisions between particles in the nebula.
What are the three key necessities for all life on Earth?
A) (1) nutrients, (2) energy, (3) liquid water B) (1) liquid water, (2) carbon, (3) oxygen C) (1) nutrients, (2) liquid water, (3) oxygen D) (1) DNA, (2) mutations, (3) liquid water E) (1) DNA, (2) liquid water, (3) oxygen
For which of the following is the celestial sphere an accurate representation of reality?
A. the view of the stars from Earth B. the motion of the planets around Earth C. the spherical bubble that surrounds Earth D. the distance to the stars E. the motion of the Sun around Earth