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Physics The Good One > 10 space > Flashcards

10 space Flashcards

1
Q

What is transmitted by the earth’s atmosphere?

A

visible

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2
Q

Why are larger mirrors used on reflector telescopes?

A

brighter images (bigger mirror collects more light)

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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

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5
Q

What are the three ways to measure distance in space?

A

Astronomical Unit (AU)

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6
Q

Astronomical Unit (AU)

A

the mean radius of the earth’s orbit (1.5e11m)

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7
Q

Astronomical unit use

A

to measure distances in our solar system

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8
Q

Light Year

A

the distance that light travels in a year (9.45e15m

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9
Q

Parsec

A

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

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10
Q

1 parsec in metres

A

3.09e16m

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11
Q

Trigonometric 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

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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

A

m

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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 absorption 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

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24
Q

B

A

blue

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25
Q

A

A

blue-white

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26
Q

F

A

white

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27
Q

G

A

yellow-white

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28
Q

K

A

orange

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29
Q

M

A

coolest spectral class

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30
Q

Sun spectral Class

A

G

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31
Q

Hertzsprung Russel Diagram Y axis

A

Absolute magnitude

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32
Q

Hertzsprung Russel Diagram X Axis

A

Spectral class / Temperature (Hot to cool

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33
Q

Small Star Life Cycle

A

Stellar Nebula

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34
Q

Stellar Nebula/protostars

A

Cloud of hydrogen in space

35
Q

Main sequence stars

A

hydrogen fuses to helium then helium fuses to heavier elements and the luminosity increases. Yellow Dwarf

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

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 rotates 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

39
Q

Doppler effect

A

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

40
Q

RedShift

A

when galaxies move away from 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 Hubble’s law

A

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

45
Q

Hubble’s law

A

V = Hd

46
Q

How to work out the age of the universe

A

1/ Hubble constant

47
Q

History of the universe

A

the big bang (rapid inflation

48
Q

Evidence for the big bang

A

hydrogen:helium ratio

49
Q

How is the hydrogen:helium ratio 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 big bang

51
Q

Steady state

A

an alternative universe theory suggesting 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

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

56
Q

Critical/ flat universe

A

the universe’s density is perfect; it will expand 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 supernova)

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)

61
Q

Sun’s life cycle of a star (fusion based)

A

The Sun is fusing hydrogen into helium in its core. When hydrogen fusion ceases

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

if 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

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

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

70
Q

Critical density

A

Density is large enough to prevent the Universe expanding forever 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 Hubble’s constant

A

since the start of time

74
Q

Why is it hard to predict the fate of the universe

A

because dark matter is undetectable

75
Q

Dark matter

A

matter we can’t detect that exists in space

76
Q

Dark matter examples

A

black holes

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

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)

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

84
Q

Red giant/ super giant

A

truncated main sequence stars

Physics The Good One (16 decks)

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