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ASTROPHYSICS Flashcards

1
Q

what is the universe?

A

a large collection of billions of galaxies

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2
Q

what is a galaxy?

A

a large collection of billions of stars

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3
Q

what galaxy is our solar system in?

A

the Milky Way

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4
Q

what causes moons to orbit planets?

A

gravitational force

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5
Q

what causes planets to orbit the sun?

A

gravitational force

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6
Q

what causes artificial satellites to orbit the earth?

A

gravitational force

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7
Q

what causes comets to orbit the sun?

A

gravitational force

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8
Q

describe the orbit of a comet:

A
  • highly elliptical
  • causes speed to change as the distance from the sun changes
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9
Q

describe the orbit of a moon:

A
  • circular
  • the closer the moon is to the planet, the shorter the time it will take to orbit
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10
Q

describe the orbit of a planet:

A
  • slightly elliptical
  • orbit at different distances from the sun
  • orbit at different speeds
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11
Q

relationship between orbital speed, orbital radius and time period:

A

orbital speed= (2 x pie x orbital radius)/ time period

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12
Q

why does gravitational field strength vary?

A

the more mass an object has, the greater its gravitational field will be

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13
Q

P2 stage one for how we reached today:

A

THE BIG BANG
time begins and space is created

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14
Q

P2 stage two for how we reached today:

A

INFLATION
the universe ‘inflates’ in size very quickly

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15
Q

P2 stage three for how we reached today:

A

NUCLEOSYNTHESIS
the very lightest nuclei, like hydrogen and helium are formed, the temperature is one billion kelvin

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16
Q

P2 stage four for how we reached today:

A

RECOMBINATION
nuclei and electrons combine to make neutral elements, the cosmic microwave radiation is created

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17
Q

P2 stage five for how we reached today:

A

STAR FORMATION
clouds of gas begin to condense into stars, some of the heavier elements are created in their cores

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18
Q

P2 stage six for how we reached today:

A

GALAXY FORMATION
galaxies and clusters of galaxies begin to form, the first stars begin to die, creating heavier elements

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19
Q

P2 stage seven for how we reached today:

A

SOLAR SYSTEM FORMATION
our solar system is formed, it exists in the Milky Way galaxy, part of our local group of galaxies

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20
Q

P2 stage eight for how we reached today:

A

TODAY
the universe has existed pretty much how we see it now for the past 5 billion years

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21
Q

P2 how is cosmic microwave background radiation created?

A

RECOMBINATION
nuclei and electrons combine to make neutral elements, the cosmic microwave radiation is created

22
Q

P2 evidence in favour of the big bang theory (1):

A

everything in the universe is moving away from everything else, if we reverse the expansion, we find that everything started at one point (the Big Bang)

23
Q

P2 evidence in favour of the big bang theory (2):

A
  • 380,000 years after the Big Bang, protons and electrons combined to produce neutral hydrogen atoms, this radiated light
  • as the universe cooled and expanded, the wavelength of this energy was shifted into the microwave region of the EM spectrum
24
Q

P2 evidence in favour of the big bang theory (3):

A
  • the CMBR has stretched during expansion and cooling, so the universe must have been smaller and hotter in the past
  • today, we can detect the 1mm microwave radiation throughout the universe, the same in whichever direction we look.
25
P2 what is redshift and blueshift?
because objects in space move quickly, their doppler shifts are measurable, by measuring the doppler shift we can measure how fast a galaxy is moving
26
P2 what happens if a wave is moving relative to an observer?
there will be a change in the observed frequency and wavelength
27
P2 equation relating to change in wavelength, reference wavelength, velocity of a galaxy and speed of light:
change in wavelength/ reference wavelength = velocity of a galaxy/ speed of light
28
P2 what are star's brightness represented by on a standard scale?
- absolute magnitude - scale is centred 0 - brighter stars have a negative absolute magnitude - dimmer stars ave positive absolute magnitude
29
how does the red- shift in light relate differ at different distances from the earth?
The further away a galaxy is the greater its red-shift and hence the faster it is moving away from us
30
what class of star is blue?
O
31
what class of star is deep blue white?
B
32
what class of star is blue white?
A
33
what class of star is yellowish white?
G
33
what class of star is white?
F
34
what class of star is pale yellow orange?
K
35
what class of star is light orange red?
M
36
what colour star is the hottest?
Blue
37
what colour star is the coolest?
light orange red
38
what is a nebula?
a star begins its life as a cloud of gas and dust called a nebula
39
Once a nebula is formed, ...... causes the gas to condense, and it eventually gets hot and dense enough for fusion to begin. The star lives most of its life as a .......
- gravity - main sequence star
40
once the ........ runs out of fuel, it swells up to become a .......
- main sequence star - red giant
41
once a ...... is formed, less massive stars become unstable and throw off their outer layers, leaving a small hot-white ember behind, this is called a ......
- red giant - white dwarf
42
more massive stars collapse and begin to fuse ......... into heavier elements, the balance between gravity and fusion shifts and eventually the star explodes into a ........
- helium - supernova
43
after a ......., the lighter stars collapse inward. The nuclei and their individual nucleons are crushed into pure .... to create a ......... ......
- supernova - neutrons - neutron star
44
after a ......, the more massive stars continue collapsing inwards until they reach a point of ........ ........, creating a ........ ......
- supernova - infinite density - black hole
45
P2 where do main sequence stars go on a hertzsprung-russell diagram?
subtle s shape down the middle
46
P2 where do white dwarfs go on a hertzsprung-russell diagram?
bottom left
47
P2 where do giants go on a hertzsprung-russell diagram?
just above s line to the right
48
P2 where do supergiants go on a hertzsprung-russell diagram?
above giants top right
49
how does red-shift of galaxies support the big bang theory?
- the further the galaxy is fro earth, the greater the red shift - the greater the red sift, the faster the galaxy is moving away - speed of galaxies increases with increased distance
50
what is absolute magnitude?
- because stars exist at wildly different distances from earth, their brightness is represented on a standard scale, called absolute magnitude

PHYSICS (10 decks)

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