Section 12.A

Question 1

Realize a cloud of gas and dust fragments as it _________, until pieces (not the whole cloud) ________ to become individual stars.

Answer 1

• collapses

- collapse

Question 2

When a cloud fragment contracts, its internal motions are enhanced.

Answer 2

 Recognize the three kinds of internal motion that are enhanced and what results from each.

Question 3

Recognize that, while collapse happens, ___________, just as wet spinning pottery loses
material outward but not upward or downward.

Answer 3

the outer, looser portions flatten to become a disk,

Question 4

the center portion of the collapsing gases that are becoming a star system

Answer 4

Protostar

Question 5

____________ slows and eventually stops the collapse of a star (e.g. stronger you squeeze a sponge the more it resists).
 When the pressure has built up enough to heat the core to 3 million degrees, nuclear fusion starts and adds extra support.

Answer 5

Pressure build-up

Question 6

Recognize a star entirely stops collapsing _____

Identify this point as when the star hits the _____ on the ____

Answer 6

• once nuclear fusion has begun.

- Main Sequence - H-R Diagram

Question 7

Realize the reason for “failed stars” is they are ______________________________

Answer 7

too lightweight to get hot enough inside for nuclear reactions to occur.