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A-Level PHYSICS Edexcel > Topic 10 -Space > Flashcards

Topic 10 -Space Flashcards

1
Q

what is transmitted by the earths atmosphere?

A

visible
microwave
some radio

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2
Q

Why are larger mirros used on reflector telescopes?

A
  • brighter images (bigger mirror collects more light)

- Better Resolution (Light spreads out less through a bigger hole)

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3
Q

radio telescope

A

a type of reflector telescope that is very large because radio waves have a large wavelength

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4
Q

Where must optical observatories be placed?

A
  • Where there is little light pollution

- where the sky is clear

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5
Q

what are the three ways to measure distance in space?

A
  • Astronomical Unit (AU)
  • Light Year
  • Parsec
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6
Q

Astronomical Unit (AU)

A
  • the mean radius of the earths orbit (1.5e11m)
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7
Q

Astronomical unit use

A

to measure distances in out solar system

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8
Q

Light Year

A

the distance that light travels in a year (9.45e15m, using s = vt)

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9
Q

Parsec

A

the distance when the paralax angle is 1 arcsecond (1/3600degrees)

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10
Q

1 parsec in metres

A

3.09e16m

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11
Q

Trignometric parallax uses

A

measure distances to nearby stars

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12
Q

trigonometric parallax

A

The star is viewed from two positions at 6 month intervals
The change in angular position of the star against background of fixed stars
is measured
Trigonometry is used to calculate the distance to the star
The diameter/radius of the Earth’s orbit about the Sun must be known

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13
Q

Trigonometric parallax as the angle decreases in size…

A

the object gets more distant

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14
Q

Apparent Magnitude letter

A

m

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15
Q

Apparent Magnitude, m

A

how bright the star appears to someone on earth.

The smaller the number the brighter the star

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16
Q

Absolute Magnitude letter

A

M

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17
Q

Absolute Magnitude

A

how bright a star would appear if it were at a distance of 10pc from the observer

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18
Q

magnitude distance equation

A

m - M = 5log(d/10)

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19
Q

Wiens Law

A

a relationship between the peak wavelength of the spectrum and the temperature of the black body

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20
Q

wiens law equation

A

λmax T = 0.0029

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21
Q

spectral class

A

represents the temperature of a star (related to the absorbtion lines on hydrogen)

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22
Q

Spectral class order

A

OBAFGKM

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23
Q

O

A

hottest spectral class, blue, 25 000 - 50 000 K

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24
Q

B

A

blue, 11 000 - 25 000 K

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25
Q

A

A

blue-white, 7500 - 11 000 K

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26
Q

F

A

white, 6000 - 7500 K

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27
Q

G

A

yellow-white, 5000-6000K

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28
Q

K

A

orange, 3500-5000K

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29
Q

M

A

coolest spectral class, red, <3500K

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30
Q

Sun spectral Class

A

G

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31
Q

Hertzsprung Russel Diagram Y axis

A

Absolute magntitude

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32
Q

Hetzsprung Russel Diagram X Axis

A

Spectral class / Temperature (Hot to cool, logarithmic)

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33
Q

Small Star Life Cycle

A
  • Stella Nebula
  • protostar
  • yellow dwarf
  • red giant
  • planetary nebula
  • white dwarf
  • black dwarf
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34
Q

Stellar Nebula/protostars

A

Cloud of hydrogen in space, protostars form when there is enough pressure for fusion.

35
Q

Main sequence stars

A

hydrogen fuses to helium then helium fuses to heavier elements and the luminosity increases.
Yellow Dwarf, Blue giant, Red giant, Red super giant

36
Q

Stellar remnants (for small stars)

A

The carbon core contracts until its only supported by electron pressure.
When the excess gas/dust is lost a white dwarf is left which will eventually cool and fade to a black dwarf.

37
Q

Stellar remnants (for large stars)

A

the star collapses.
If the collapse of the core can be stopped by neutron pressure the star becomes a neutron star which rapidly toates and sends out pulsars.
Else if the neutron pressure cannot withstand gravity it collapses into a black hole.

38
Q

Life cycle of a large star

A
  • stellar nebula
  • proto star
  • blue super giant
  • red super giant
  • black hole or neutron star
39
Q

Doppler effect

A

the frequency of the wave is increased/reduced because an object is moving towards/away from a reciever

40
Q

RedShift

A

when galaxies move away us

41
Q

BlueShift

A

when galaxies move towards us

42
Q

How can you tell if redshift/blueshift is occurring?

A

the lines of the absorption spectra have shifted. All absorption spectra should be similar as the universe is mostly made from hydrogen/helium

43
Q

redshift equation

A

change in wavelength / original wavelength = object speed / wave speed = cosmological redshift

44
Q

What is hubbles law

A

a direct correlation between the distance to a galaxy and its recessional velocity as determined by the red shift.

45
Q

hubbles law

A 
V = Hd
V = recessional velocity
H = hubble constant
d = distance
46
Q

How to work out the age of the universe

A

1/ hubble constant

47
Q

History of the universe

A
  • the big band (rapid inflation, nothing but energy)
  • fundamental particle were formed (electrons, quarks)
  • Quarks formed protons and neutrons
  • hydrogen atoms were made
  • after millions of years the first stars formed
  • after 8 billion years the solar system formed
48
Q

Evidence for the big bang

A
  • hydrogen:helium ration
  • CMBR
  • redshift/ expanding universe
49
Q

How is the hydrogen:helium ration evidence for the big bang

A

neutrons are not stable so they decay. The ratio of hydrogen to helium matches the ratio of protons to neutrons.

50
Q

Cosmic Microwave background

A

microwaves coming from every point in the sky is energy left over from the bigbang

51
Q

Steady state

A

an alternative universe theory suggesting the the universe has always been as it is. The evidence suggests that it is wrong.

52
Q

How is the accelerating expansion of the universe explained

A

dark matter and dark energy

53
Q

What are theories on how the universe can end

A
  • open
  • closed
  • critical /flat
54
Q

The big crunch

A

closed universe theory. If the universe is too dense gravity halts the expansion and the universe eventually collapses

55
Q

The big freeze/ the big rip/ heat death

A

Open universe theory. If the universe is not dense enough the universe will expand forever.

56
Q

Critical/ flat universe.

A

the universes density if perfect it will exapnd forever at a decelerating rate.

57
Q

Standard candle

A

a star with known luminosity

58
Q

cepheid variable star

A

a predictable standard candle (or supernavae)

59
Q

Uses of standard candles

A

to measure extremely long distances that can’t be measured with trigonometric parallax

60
Q

how can intensity and luminosity be used to measure distance?

A

I = L / (4πd^2)

inverse square law

61
Q

suns life cycle of a star (fusion based)

A
  • The Sun is fusing hydrogen into helium in its core.
  • When hydrogen fusion ceases the core of the Sun cools and collapses.
  • The Sun expands and becomes a red giant
  • The core becomes hot enough for helium fusion to begin in the core
  • Helium begins to run out and the core collapses again
  • The outer layers of the sun are ejected out into space
  • The temperature doesn’t rise enough for further fusion to begin so The core/Sun becomes a (white) dwarf star
62
Q

standard candle

A

a stellar object with known luminosity

63
Q

How are standard candles used

A

the standard candles flux/intensity is measured. Use the inverse square law I = L/4πd^2 to calculate the distance.

64
Q

why isn’t trigonometric parallax good for long distances

A

is the star is too distant the angle it moves by is too small so the uncertainty is too big

65
Q

how do astronomers know white dwarfs are small?

A

White dwarf stars have:
- high temperature T
- low luminosity L
L = σAT^4 means that the surface area is small

66
Q

what happens when a star cools

A

it contracts

67
Q

how to measure distances too big for standard candles

A
  • measure change in wavelength/frequency
  • deatermine relative velocity using redshift velocity
  • apply hubbles law v = Hd
68
Q

doppler shift

A

change in frequency/wavelength due to the relative motion of galaxy

69
Q

what conclusions did hubble reach

A
  • Recessional velocity ∝ galaxy distance
  • Red shift due to a galaxy moving away from Earth/observer
  • Deduction of the expanding Universe
70
Q

critical density

A

Density is large enough to prevent Universe expanding for ever but not too big to cause a collapse/contraction of the Universe

71
Q

hubble constant

A

1.8e-18

72
Q

unit of hubble constant

A

s^-1

73
Q

assumptions when calculating the age of the universe through hubbles constant

A
  • since the start of time

- galaxies travelling at constant speed

74
Q

why is it hard to predict the fate of the universe

A

the it matter which is undetectable (dark matter) which effects the mass and density of the universe

75
Q

dark matter

A

matter we can’t detect that exists in space

76
Q

dark matter examples

A

black holes, neutrinos, subatomic particles

77
Q

dark energy

A

theoretical energy that opposes gravity in space causing the universe expansion to accelerate

78
Q

horizontal axis of a HR diagram

A

surface temperature of star / spectral class

79
Q

How is the velocity of a galaxy determined

A
  • Measure wavelength of light from the galaxy
  • Compare it to the wavelength for a source on the Earth
  • Shift in line spectra due to the doppler effect
  • v/c = change in wavelength/ wavelength of source on earth
80
Q

why is it so hard to predict the fate of the universe

A
  • Due to the difficulty in making accurate measurements of distances to galaxies (Hubble constant has a large uncertainty)
  • Because of the existence dark matter changes the mass/density
  • Values of the average density/mass of the universe have a large uncertainty
  • Dark energy makes it hard to predict how gravity will determine the ultimate fate
81
Q

why is high temperature required in fusion

A

to overcome the electrostatic force of repulsion

82
Q

why is high density needed in fusion

A

to keep a high collision rate

83
Q

why do elements heavier than iron not fuse

A

Iron is the most stable element (peak of the binding energy curve). If a heavier element than iron was to fuse the binding energy per nucleon would decrease making it less stable AND THE REACTION WOULD REQUIRE AN ENERGY INPUT

84
Q

red giant/ super giant

A

truncated main sequence stars

A-Level PHYSICS Edexcel (16 decks)

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