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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
what type of star is the sun?
a red giant
26
what happens to stars when fusion begins to slow down?
it begins to swell out into a red giant or supergiant (depending on size) the surface turns red as it cools down
27
why does the surface of a star turn red?
it is cooling down
28
what happens when a star turns into a red giant?
elements such as helium fuse and heavier elements up to iron are formed in the core
29
what does a red giant eventually turn into?
a white dwarf
30
how does a red giant become a white dwarf?
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
31
why is a white dwarf called a white dwarf?
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
32
how does a white dwarf turn into a black dwarf?
they cool down and release less energy | once it stops releasing a significant amount, it turns black
33
what happens to larger stars after their long stable period ends?
they swell to become a red supergiant
34
what is the next stage in the lifecycle of a star after being a red supergiant?
a supernova
35
how does a red supergiant turn into a supernova?
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)
36
what are the two things a supernova can result in?
a black hole | a neutron star
37
how is a neutron star formed?
the neutron star is the very dense core of the supernova
38
what is a black hole?
a super dense point in space that not even light can escape from
39
how are lighter elements formed?
from nuclear fusion in the sun and stars
40
why can elements larger than iron not be formed by fusion?
too much energy is needed
41
how old is the sun?
5 billion years
42
what will happen in 5 billion years?
the sun will turn into a re giant, then a white dwarf, then a black dwarf as it stops emitting energy
43
how are elements heavier than iron formed?
a supernova explosion
44
why has all the uranium on earth not decayed by now?
very long half life
45
how are new stars and planets formed by a supernova?
forces such as gravity pull all the debris together and ensures it has every element
46
what is produced when a supernova explodes?
every known element
47
how are elements heavier than iron produced and distributed?
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
what is the orbit of the earth like?
almost circular
49
what is the force on an orbiting object?
the gravitational attraction between it and the larger body
50
what is a galaxy?
a huge collection of stars that stay together because of gravity
51
how long does it take to travel one light year?
one year
52
how many stars are in the milky way?
100 billion
53
which colour has the longest wavelength?
red
54
what increases as the speed of a star or galaxy increases
the red shift
55
what did Edward Hubble discover?(2)
the light from distant galaxies was red-shifted | the further away a galaxy is from earth, the greater the shift
56
what is happening to distant galaxies
they are moving away from earth faster than those nearest
57
what happens to the light rays of something that is moving from you?
the wavelength increases
58
why is it called the red shift?
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
what happens to the light ways of something if it is moving towards you?
they get squashed together and shifts to the blue end of the spectrum where they are most squashed
60
what is it called when something moves towards you
blue-shift
61
what is happening to the universe?
it is expanding
62
the big bang theory of expansion:
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
what is the steady state theory of expansion?
the galaxies are being pushed apart by matter entering through 'white holes'
64
evidence for the big bang theory
scientists have discovered microwaves coming from every direction in space that can only have come from the radiation released during the big bang
65
what is CMBR
Cosmic Microwave Background radiation | gamma radiation produced just after the big bng
66
what is dark matter?
the missing mass in galaxies that can't be seen
67
what will happen if the density of the universe is less than a specific amount?
it will continue expanding forever and everything will die out
68
what will happen if the density of the universe is above a specific amount?
it will stop expanding and go into reverse - the Big Crunch
69
what are the two possibilities for the end of the universe?
the Big Yawn | the Big Crunch
70
what is the big bang theory?
after the explosion of a supernova from a small, very hot and dense region, the universe is still expanding
71
what energy is thought to be causing the expansion?
'dark energy'
72
what are geostationary orbits?
the object orbits the earth in the same direction as the earth's spin, so it stays above the same place
73
when you get closer to a star or planet, what increases?
the gravitational attraction force
74
as the gravitational force increases, what much happen to the object orbiting the larger body?
its speed must increase
75
why must the speed of an orbiting object increase as the gravitational attraction increases?
it must speed up to overcome the force of attraction and avoid crashing with the bigger body and to stay in orbit
76
what happens to the speed of an orbiting object the further from the larger body it is and why?
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
what happens to the size of the orbit the further away a satellite is from earth?
it increases and takes longer to complete one orbit
78
what direction does the force of gravity from the sun act?
it acts from the centre of the sun to the planet, pulling it towards it
79
if the speed of an object in a stable orbit increases, what happens to the radius of its orbit?
it will decrease
80
what is a centripetal force?
a force acting towards the centre of a circle
81
what is the velocity of a planet?
its direction of motion
82
what to remember about the force of gravity on a planet and its direction of motion?
they are at right angles to eachother
83
why does an orbiting planet always accelerate?
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
what is the acceleration of a planet?
the change per second in its velocity
85
what happens if a satellite is released too close to earth's surface?
atmospheric drag means it gradually loses speed and crashes into earth's surface
86
what happens if a satellite is released quickly from earth?
it will fly off into space
87
what happens when a satellite is released correctly?
it moves a constant height and speed in a circular,stable orbit around the earth
88
what happens when the speed of a rocket increases to keep it constant?
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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