Chapter 13

Question 1

gravity can create stars only if..

Answer 1

it can overcome the force of thermal pressure in a cloud

Question 2

gravity within a contracting gas cloud becomes stronger as the gas what?

Answer 2

becomes denser

Question 3

gravity is working against what?

Answer 3

gravitational contraction and nuclear fusion and degeneracy pressure

Question 4

a cluster of many stars can of be formed out of what?

Answer 4

a single cloud

Question 5

dust grains heat up and emit _______ light

Answer 5

infrared

Question 6

rotation causes _____ of matter to shoot out along the rotation axis of ______

Answer 6

protostars (still in the process of forming)

Question 7

_______ ends when energy released by hydrogen fusion ____ energy radiated from the surface

Answer 7

Contraction

fusion

Question 8

a ______ contracts and heats until the core temperature is sufficient for hydrogen fusion

Answer 8

protostar

Question 9

it took the sun _____ years, to change from protosar to main sequence

Answer 9

30 million years (less time for more massive stars)

Question 10

gravity causes ______ and _______ cloud to shrink

Answer 10

cold and dense cloud

Question 11

when the core gets hot enough, ____ begins and stops the shrinking

Answer 11

fusion

Question 12

what are brown dwarfs?

Answer 12

starlike objects not massive enough to start fussion

Question 13

______________ halts the contraction of objects (brown dwarfs) before the temperature becomes hot enough for fusion

Answer 13

Degeneracy Pressure

Question 14

what would happen to stars more massive than 300MSun?

Answer 14

would blow apart

Question 15

what happens to stars less massive than 0.08Msun?

Answer 15

they cant sustain fusion

Question 16

what happens when a star like the sun can no longer fuse hydrogen to helium in its core?

Answer 16

its core shrinks and heats up

Question 17

what happens when the two helium nuclei don’t work?

Answer 17

helium fusion must combine 3 He nuclei to make carbon

Question 18

___________ does not begin right away because it requires higher temperatures than hydrogen fusion

Answer 18

helium fusion

Question 19

the core temperature rises rapidly when…

Answer 19

helium fusion burns

Question 20

Double Shell burning ends with a pulse that ejects the H and He into space as a _______ (no longer gravitationally bound)

Answer 20

planetary nebula

Question 21

(planetary nebulae)

the core left behind becomes a white dwarf, which is ____ and ______

Answer 21

hotter and dimmer

Question 22

multiple burning shell.

advanced nuclear burning proceeds in ______________

Answer 22

a series of nested shells

Question 23

_____ is a dead end for fusion

Answer 23

iron

Question 24

iron has the lowest what?

Answer 24

mass per nuclear particle

Question 25

neutrons collapse to the center, forming what?

Answer 25

neutron star

Question 26

energy and neutrons released in a ___________ enable elements heavier than iron to form. including Gold and U

Answer 26

supernova explosion

Question 27

what determines a stars entire life?

Answer 27

its mass

Question 28

_____ mass stars have short lives, eventually becoming hot enough to make iron, and end in supernova explosions

Answer 28

high

Question 29

low mass stars have long lives, ____ become hot enough to fuse carbon nuclei, and end as white dwarfs

Answer 29

never

Question 30

low-mass star summary | __________: leaves white dwarf behind

Answer 30

planetary nebula

Question 31

high mass star | _________ leaves a neutron star or black hole behind

Answer 31

supernova

Question 32

very massive stars are what

Answer 32

rare