Chapter 13 Flashcards

1
Q

gravity can create stars only if..

A

it can overcome the force of thermal pressure in a cloud

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2
Q

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

A

becomes denser

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3
Q

gravity is working against what?

A

gravitational contraction and nuclear fusion and degeneracy pressure

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4
Q

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

A

a single cloud

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5
Q

dust grains heat up and emit _______ light

A

infrared

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6
Q

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

A

protostars (still in the process of forming)

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7
Q

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

A

Contraction

fusion

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8
Q

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

A

protostar

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9
Q

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

A

30 million years (less time for more massive stars)

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10
Q

gravity causes ______ and _______ cloud to shrink

A

cold and dense cloud

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11
Q

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

A

fusion

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12
Q

what are brown dwarfs?

A

starlike objects not massive enough to start fussion

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13
Q

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

A

Degeneracy Pressure

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14
Q

what would happen to stars more massive than 300MSun?

A

would blow apart

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15
Q

what happens to stars less massive than 0.08Msun?

A

they cant sustain fusion

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16
Q

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

A

its core shrinks and heats up

17
Q

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

A

helium fusion must combine 3 He nuclei to make carbon

18
Q

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

A

helium fusion

19
Q

the core temperature rises rapidly when…

A

helium fusion burns

20
Q

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

A

planetary nebula

21
Q

(planetary nebulae)

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

A

hotter and dimmer

22
Q

multiple burning shell.

advanced nuclear burning proceeds in ______________

A

a series of nested shells

23
Q

_____ is a dead end for fusion

A

iron

24
Q

iron has the lowest what?

A

mass per nuclear particle

25
Q

neutrons collapse to the center, forming what?

A

neutron star

26
Q

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

A

supernova explosion

27
Q

what determines a stars entire life?

A

its mass

28
Q

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

A

high

29
Q

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

A

never

30
Q

low-mass star summary

__________: leaves white dwarf behind

A

planetary nebula

31
Q

high mass star

_________ leaves a neutron star or black hole behind

A

supernova

32
Q

very massive stars are what

A

rare