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Physics⚡️ > Chapter 16 - Space > Flashcards

Chapter 16 - Space Flashcards

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1
Q

what is a comet?

A

a lump of frozen rock that orbits the sun

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2
Q

what are meteors?

A

rocks that burn up when they enter the earth’s atmosphere

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3
Q

why do you only see comets when they are near the sun?

A

they heat up so much that they emit light

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4
Q

the shape of the orbit of a comet

A

elliptical (squashed circle)

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5
Q

how did the sun form?

A

clouds of dust and gas were pulled together by gravitational attraction

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6
Q

how was the solar system formed?

A

the heat from the sun drove the gas in the atmosphere away, creating rocky planets close to the sun and gassy planets farther away

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7
Q

what is a protostar?

A

a star-to-be

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8
Q

how is a protostar formed?

A

the clouds of particles are pulled together by forces of attraction so they speed up and collide with more force. This merges the clouds together and a protostar is formed

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9
Q

describe the process by which a protostar turns into a star

A

a protostar becomes denser, meaning the particles have more energy and speed up, increasing the temperature
if the protostar becomes hot enough, hydrogen nuclei fuse and form helium nuclei
this releases huge amounts of energy which makes the star shine

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10
Q

where is energy transferred from/to in the formation of a star?

A

gravitational energy store to thermal energy store

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11
Q

what happens to objects formed that are too small to become stars?

A

they turn into planets orbiting the star

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12
Q

what is a main sequence star?

A

it is in the middle of the long, stable period which is the main stage in the life of a star

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13
Q

how long does the stable period last?

A

normally several billion years

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14
Q

what is the heaviest known natural element?

A

uranium

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15
Q

half life of uranium

A

4.5 billion years

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16
Q

what makes a star stable?

A

when the outward force of fusion trying to expand the star and the force of gravity pulling everything inwards are balanced

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17
Q

when does the stable period of a star end?

A

when most of the hydrogen nuclei have fused to form helium nuclei

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18
Q

why can a comet not be seen when it is far away from the sun?

A

doesn’t absorb enough energy to burn

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19
Q

one difference between a comet and an asteroid

A

asteroids are made of rocky material and metals but comets are made of ice, dust and rocky material

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20
Q

one similarity between a comet and an asteroid

A

both orbit the sun

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21
Q

largest planet in the solar system

A

jupiter

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22
Q

planet nearest the sun

A

mercury

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23
Q

why is earth likely to be the only planet where liquid water can exist?

A

its position in the solar system means it has a temperature between 0 and 100 degrees - the conditions needed for liquid water

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24
Q

why is uranium evidence that the solar system must have formed from a supernova?

A

they can make other heavier elements by bombarding uranium with neutrons which would have been found in the supernova

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25
Q

what type of star is the sun?

A

a red giant

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26
Q

what happens to stars when fusion begins to slow down?

A

it begins to swell out into a red giant or supergiant (depending on size)
the surface turns red as it cools down

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27
Q

why does the surface of a star turn red?

A

it is cooling down

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28
Q

what happens when a star turns into a red giant?

A

elements such as helium fuse and heavier elements up to iron are formed in the core

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29
Q

what does a red giant eventually turn into?

A

a white dwarf

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30
Q

how does a red giant become a white dwarf?

A

It becomes unstable as no more radiation is released
Gravity forces the star to collapse in on itself
This core heats as it collapses, turning from red to white

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31
Q

why is a white dwarf called a white dwarf?

A

the heating of the core of the star turns it from red to white and the collapse of the outer layers means it is much smaller than before

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32
Q

how does a white dwarf turn into a black dwarf?

A

they cool down and release less energy

once it stops releasing a significant amount, it turns black

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33
Q

what happens to larger stars after their long stable period ends?

A

they swell to become a red supergiant

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34
Q

what is the next stage in the lifecycle of a star after being a red supergiant?

A

a supernova

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35
Q

how does a red supergiant turn into a supernova?

A

the star collapses as there isn’e enough energy for fusion
the star gets compressed by gravity and the particles
this compression suddenly reverses, causing an explosion (a supernova)

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36
Q

what are the two things a supernova can result in?

A

a black hole

a neutron star

37
Q

how is a neutron star formed?

A

the neutron star is the very dense core of the supernova

38
Q

what is a black hole?

A

a super dense point in space that not even light can escape from

39
Q

how are lighter elements formed?

A

from nuclear fusion in the sun and stars

40
Q

why can elements larger than iron not be formed by fusion?

A

too much energy is needed

41
Q

how old is the sun?

A

5 billion years

42
Q

what will happen in 5 billion years?

A

the sun will turn into a re giant, then a white dwarf, then a black dwarf as it stops emitting energy

43
Q

how are elements heavier than iron formed?

A

a supernova explosion

44
Q

why has all the uranium on earth not decayed by now?

A

very long half life

45
Q

how are new stars and planets formed by a supernova?

A

forces such as gravity pull all the debris together and ensures it has every element

46
Q

what is produced when a supernova explodes?

A

every known element

47
Q

how are elements heavier than iron produced and distributed?

A

the force of a red supergiant collapsing is great enough to force two smaller nuclei to fuse into a bigger one and the explosion of a supernova distributes them all over the universe

48
Q

what is the orbit of the earth like?

A

almost circular

49
Q

what is the force on an orbiting object?

A

the gravitational attraction between it and the larger body

50
Q

what is a galaxy?

A

a huge collection of stars that stay together because of gravity

51
Q

how long does it take to travel one light year?

A

one year

52
Q

how many stars are in the milky way?

A

100 billion

53
Q

which colour has the longest wavelength?

A

red

54
Q

what increases as the speed of a star or galaxy increases

A

the red shift

55
Q

what did Edward Hubble discover?(2)

A

the light from distant galaxies was red-shifted

the further away a galaxy is from earth, the greater the shift

56
Q

what is happening to distant galaxies

A

they are moving away from earth faster than those nearest

57
Q

what happens to the light rays of something that is moving from you?

A

the wavelength increases

58
Q

why is it called the red shift?

A

as something moves away from you, like the galaxy, the wavelength increases
it is shifted to the red end of the spectrum as this is where the waves are longest

59
Q

what happens to the light ways of something if it is moving towards you?

A

they get squashed together and shifts to the blue end of the spectrum where they are most squashed

60
Q

what is it called when something moves towards you

A

blue-shift

61
Q

what is happening to the universe?

A

it is expanding

62
Q

the big bang theory of expansion:

A

everything started in a very small and dense area
the big band explosion started things off and expanded to the universe we know today
although it is much slower, expansion is still happening because of the big bang

63
Q

what is the steady state theory of expansion?

A

the galaxies are being pushed apart by matter entering through ‘white holes’

64
Q

evidence for the big bang theory

A

scientists have discovered microwaves coming from every direction in space that can only have come from the radiation released during the big bang

65
Q

what is CMBR

A

Cosmic Microwave Background radiation

gamma radiation produced just after the big bng

66
Q

what is dark matter?

A

the missing mass in galaxies that can’t be seen

67
Q

what will happen if the density of the universe is less than a specific amount?

A

it will continue expanding forever and everything will die out

68
Q

what will happen if the density of the universe is above a specific amount?

A

it will stop expanding and go into reverse - the Big Crunch

69
Q

what are the two possibilities for the end of the universe?

A

the Big Yawn

the Big Crunch

70
Q

what is the big bang theory?

A

after the explosion of a supernova from a small, very hot and dense region, the universe is still expanding

71
Q

what energy is thought to be causing the expansion?

A

‘dark energy’

72
Q

what are geostationary orbits?

A

the object orbits the earth in the same direction as the earth’s spin, so it stays above the same place

73
Q

when you get closer to a star or planet, what increases?

A

the gravitational attraction force

74
Q

as the gravitational force increases, what much happen to the object orbiting the larger body?

A

its speed must increase

75
Q

why must the speed of an orbiting object increase as the gravitational attraction increases?

A

it must speed up to overcome the force of attraction and avoid crashing with the bigger body and to stay in orbit

76
Q

what happens to the speed of an orbiting object the further from the larger body it is and why?

A

it slows down

the force of gravity on the object is less so it doesn’t need to travel as fast to stay in orbit

77
Q

what happens to the size of the orbit the further away a satellite is from earth?

A

it increases and takes longer to complete one orbit

78
Q

what direction does the force of gravity from the sun act?

A

it acts from the centre of the sun to the planet, pulling it towards it

79
Q

if the speed of an object in a stable orbit increases, what happens to the radius of its orbit?

A

it will decrease

80
Q

what is a centripetal force?

A

a force acting towards the centre of a circle

81
Q

what is the velocity of a planet?

A

its direction of motion

82
Q

what to remember about the force of gravity on a planet and its direction of motion?

A

they are at right angles to eachother

83
Q

why does an orbiting planet always accelerate?

A

it is constantly changing direction
gravity changes its velocity to pull the planet towards the sun but because the planet is already moving, it just changes its direction rather than making it fall towards the sun

84
Q

what is the acceleration of a planet?

A

the change per second in its velocity

85
Q

what happens if a satellite is released too close to earth’s surface?

A

atmospheric drag means it gradually loses speed and crashes into earth’s surface

86
Q

what happens if a satellite is released quickly from earth?

A

it will fly off into space

87
Q

what happens when a satellite is released correctly?

A

it moves a constant height and speed in a circular,stable orbit around the earth

88
Q

what happens when the speed of a rocket increases to keep it constant?

A

the increase in speed moves it to a higher orbit, where the increased distance means it moves slower, keeping it constant

Physics⚡️ (16 decks)

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