P. 471 Answers

1. Stars form from huge clouds of dust and gases called nebulas. The dust and gases swirl around, forming clumps. These clumps attract each other because of gravity and grow larger and larger. When they are large and dense enough, they begin to produce large amounts of light energy and other forms of energy.

2. Low-mass stars cool down and swell up into a red giant. Outer layers drift away

and the star shrinks to become a white dwarf which will cool and fade away. High-mass stars swell into red super-giants

which undergo a supernova. This leaves behind either a neutron star or a black hole depending on the mass of the original star.

3. A supernova is a type of explosion that occurs when the source of energy of a high-mass star is used up. The outer layers of the star expand outward rapidly.