Astrophysics Flashcards
1
Q
What is a satellite?
A
Anything’s that orbits a planet
—> can either be natural or artificial
2
Q
What is an example of a natural satellite?
A
The moon
3
Q
What is an example of an artificial satellite?
A
Communication satellites
Orbiting telescopes
4
Q
The sun is the …?
A
Central star
5
Q
What is the order of planets?
A
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
6
Q
How do the planets orbit the sun?
A
In an elliptical orbit
7
Q
What is an elliptical orbit?
A
The path the planets take which isn’t a perfect circle (slightly squashed)
8
Q
What is an asteroid made of?
A
Rock and metal
9
Q
Where is an asteroid found?
A
The asteroid belt
10
Q
Where is the asteroid belt?
A
Between Mars and Jupiter
11
Q
What is a comet made of?
A
Ice and dust
12
Q
What do comets do?
A
Orbit the sun but have much more elliptical orbits
13
Q
Where do comets often travel?
A
To the very outskirts of the solar system
14
Q
What is a galaxy?
A
Collections of billions of stars
15
Q
Which is the most stable atom made in a star?
A
Iron
16
Q
What gas is the main component of a nebula cloud?
A
Hydrogen
17
Q
What is the temperature of the sun?
A
6000K
18
Q
What does ‘K’ stand for?
A
Kelvin
19
Q
When is the speed of a comet at a minimum?
A
When it is furthest from the sun
20
Q
When is the speed of a comet at a maximum?
A
When it is closest to the sun
21
Q
What is a planet?
A
A body which orbits a star
22
Q
What is a moon?
A
A body which orbits a planet
23
Q
What is the name of our galaxy?
A
The Milky Way galaxy
24
Q
What colour is the coolest star?
A
Yellow
25
What colour is the hottest star?
Blue
26
Our solar system a tiny speck about halfway along one of …?
The Milky Way’s spiral arms
27
What is the force holding all the stars together?
Gravity
28
How do stars orbit a galaxy?
They all spin around the middle in the same way that planets orbit the sun
29
What is the universe?
A collection of billions of galaxies
30
What is a solar system?
Our sun and all of the orbiting planets
31
What is a star system?
Star being orbited by planets
32
Order of size of the ‘things’ in our universe
Satellite
Planet
Solar system
Galaxy
Universe
33
What is an orbit?
The curved path of one celestial object or spacecraft around another celestial object
34
What is Newton’s first law?
An object travelling at a certain velocity will continue to travel at that velocity unless acted upon by a resultant force
35
What is always the same about the moon?
Speed of the moon is ALWAYS the same
36
What is constantly changing in the moon?
The direction
37
What does the direction of the moon constantly changing mean?
The velocity is constantly changing
38
Every time the moon changes direction as it orbits it is …?
Accelerating (even though it is not getting any faster or slower)
39
What two forces keep a steady orbit?
Instantaneous velocity
Gravitational pull
40
What does instantaneous velocity mean?
The speed and direction of an object at one exact movement in time
41
What is the speed of the moon?
1023 m/s
42
What is gravitational pull?
An attractive force towards the earth
43
Even the the gravitational pull is strong …
It isn’t strong enough to completely pull the moon in towards the earth
44
What does velocity measure?
The speed
The direction
45
What would happen if the moon’s orbit was pulled closer to the earth?
The distance between the moon and Earth would be much smaller and so the gravitational force will be greater
—> the moon would get sucked in towards the earth
46
How would the moon avoid being sucked in towards the earth if its orbit was closer to the earth?
The moon would have to start travelling much faster so that the instantaneous velocity increase
—> allow it to maintain a stable orbit and not be pulled in towards the earth
47
The smaller an object’s orbit the …?
Faster the object
48
Equation for orbital speed
2 x pi x orbital radius
——————————
Time period
49
What is the orbital radius measured in?
Metres (m)
50
What is the time period measured in?
Seconds (s)
51
What is a nebula?
A cloud of dust and gas
52
What happens to a nebula over time?
Gravity pulls the dust and gas together to form a structure called a protostar
53
What happens as more particles collide and join the protostar?
It gets bigger and bigger
54
What is a protostar?
A collapsed nebula
55
What happens when the protostar gets bigger and bigger?
Force of gravity gets even stronger which allows it to contract more dust and gas
56
What happens when gravity squeezes the protostar?
It makes it more dense
—> the particles inside collide with each other more often
—> raises the temperature of the protostar
57
What happens when the pressure and temperature of a protostar gets high enough?
Hydrogen nuclei start to fuse together to form helium nuclei
58
What is it called when hydrogen nuclei start to fuse together to form helium nuclei?
Nuclear fusion
59
What does nuclear fusion give out loads of?
Energy
—> which keeps the core of the star hot
60
After the protostar undergoes nuclear fission what is it now called?
A main sequence star
61
What stage of star is our sun?
A main sequence star
62
What is the outward pressure (of a main sequence star) caused by?
All the energy being released by nuclear fusion
63
What is the inward pressure (of a main sequence star) caused by?
Gravity
64
How are outward and inward pressure balanced?
Perfectly balanced
65
How long do main sequence stars last?
Long stable period (billions of years)
66
What will happen at some point to the main sequence star?
Will start to run out of hydrogen and won’t be able to do any more nuclear fusion
67
When the main sequence star starts running out of hydrogen what happens to the inward pressure?
The inward pressure of gravity will take over and contract the star into a small ball until it’s so hot and dense that nuclear fusion can start again
—> star will expand again
68
What happens when the main sequence star starts to expand again?
Will form heavier elements
—> including all elements up to iron on the periodic table
69
How much the main sequence star expands depends on what?
How big the initial star was
70
If the main sequence star was initially small/medium (our sun) what will it form?
A red giant
71
If the main sequence star was initially really big what will it form?
A red super giant
72
Which reaction allows stars to emit light?
Nuclear fusion
73
Red giants and red super giants complete their life cycles in …?
Different ways
74
What happens to a red giant after a short amount of time?
Becomes unstable and expels its outer layers of dust and gas
75
What does a red giant leave behind when it expels its outer layers of dust and gas?
A hot, dense, solid core (a white dwarf)
—> doesn’t do nuclear fusion
76
What is a white dwarf?
A hot, dense, solid core
Relatively small
77
Why does a white dwarf appear white?
It gives off lots of light
78
What happens to a white dwarf over time?
Gets cooler and darker as it emits all of its energy until it transitions to a black dwarf
79
Why does a black dwarf appear dark?
No longer has enough energy to emit light
80
Which star follows a white dwarf?
Black dwarf
81
Which star follows a planetary nebula?
White dwarf
82
Which star follows a red giant?
Planetary nebula
83
Which star follows a main sequence star (for stars similar size to our sun)?
Red giant
84
Which star follows a main sequence star (for stars that are really big)?
Red super giant
85
Red super giants start to …?
Shine brightly again as they undergo even more nuclear fusion
86
What happens when a red super giants undergoes even more nuclear fusion?
After passing through several cycles of expansion and contraction they eventually explode into a supernova
87
What does a supernova form?
Elements heavier than iron that get ejected all across the universe
88
What happens to the supernova if the initial star was very big?
It will condense into a very dense core called a neutron star
89
What happens to the supernova if the initial star was absolutely massive?
Might collapse on itself and become a black hole
90
Because black hole are so dense what can they do?
Their gravity is able to pull in any light that passes nearby
91
What do black holes appear as?
Empty spaces or tiny holes in the universe where no light is emitted
92
What is a black hole?
A regional of space which is extremely dense
93
What is the most dense area of the universe?
Black holes
94
What two possible out comes could exist after a supernova explosion?
Neutron star
Black hole
95
What is a supernova?
An exploding star which can outshine a whole galaxy
96
What is the orbital time period of a planet?
Time taken to complete one orbit of another object
97
How is the value of ‘g’ related to the radius of a planet?
The bigger the radius the smaller the value of ‘g’
98
What force causes one object to orbit another?
Gravitational force of attraction
99
How does a planetary nebula form?
When a red giant runs out of fuel
100
What happens when the outer layers of a planetary nebula drift off into space?
It forms a glowing cloud of gas (a white dwarf)
