1. light is the fastest-known entity in our universe.

true or false

2. there are fewer than one billion stars in the galaxy.

true or false

3. hydrogen atoms do not repel each other within a star.

true or false

4. sky maps show celestial spheres, including constellations.

true or false

5. which of h following happens during the main-sequence stage of a star's life?

a) it cycles, appearing brighter and dimmer in turns.

b) it changes the color that it emits.

c) it increases its distance from the sun.

d) it grows continuously smaller and dimmer.