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Year 10 MMS > Universe - Overall Study > Flashcards

Universe - Overall Study Flashcards

1
Q

What are all stars born out of?

A

Stellar nebula; molecular cloud

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2
Q

State the life cycle of a massive star

A

Stellar nebula –> massive star –> red supergiant –> supernova –> black hole or neutron star

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3
Q

State the life cycle of an average star

A

Stellar nebula –> average star –> red giant –> planetary nebula –> white dwarf

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4
Q

Define luminosity in terms of a star’s energy.

A

The rate at which a star produces energy

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5
Q

Which spectrum shows the true colour of a star?

A

Emission spectrum

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6
Q

TRUE or FALSE

The lower the number in the B-V colour index, the bluer the star.

A

True

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7
Q

What is the blue and green filters used to find the colour of stars called?

A

B-V Colour Index

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8
Q

What is the colour of a star dependent on?

A

Temperature

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9
Q

When two hydrogen atoms fuse, what element is created?

A

Helium

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10
Q

What process does a star produce its energy from?

A

Nuclear fusion

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11
Q

Who proposed the heliocentric model?

A

Nicolaus Copernicus

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12
Q

Who proposed the geocentric model?

A

Claudius Ptolemy

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13
Q

How does a geocentric and heliocentric model differ?

A

Geocentric: Earth at the centre
Heliocentric: Sun at the centre

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14
Q

Where is the best place for an optical telescope to be placed?

A

At a high altitude with low light pollution.

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15
Q

TRUE or FALSE

The further away a star, the more it appears to move due to parallax.

A

False

It appears to move less.

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16
Q

What is the formula for calculating distance to a star in parsecs?

A

Distance to star (in pc) = 1
———————–
parallax angle in arcseconds

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17
Q

How do we know the universe is moving away from us?

A

Because when astronomers look at the spectra from distant galaxies, they find the emission lines are commonly shifted towards the red part of the spectrum

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18
Q

How are galaxies classified?

A

Their shape according to the Hubble galaxy classification scheme.

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19
Q

How do we know about other planets outside the Milky Way?

A

Because planets don’t emit light, they only reflect it from stars, they create miniature eclipses when passing in front of their stars

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20
Q

What is the limit (of distance) that parallax is used?

A

Around 100 light years

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21
Q

How fast does light travel?

A

300 million metres per second (3*10^8m/s)

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22
Q

Define Hubble’s Law.

A

The further away a galaxy is, the faster it is moving away from Earth.

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23
Q

Define recessional velocity.

A

The relative rate at which a star is moving away from Earth

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24
Q

Define dark energy

A

A theoretical force responsible for accelerating the expansion of the universe

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25
Q

Define dark matter

A

Matter that does not emit light and is responsible for unidentified gravity in the universe

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26
Q

Define observable universe

A

The spherical region of the universe that can be observed from Earth because light has had time to reach Earth.

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27
Q

Define epoch of recombination.

A

The part in time where electrons and ions could combine to form atoms.

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28
Q

Define cosmic microwave background

A

Electromagnetic radiation left over from the early stages of the universe.

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29
Q

Define singularity.

A

A point at which an infinitely dense matter occupies an infinitely small space.

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30
Q

Define big bang

A

The large explosion that scientists believe created the universe.

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31
Q

Define goldilocks zone.

A

The habitable zone around a star where the temperature is not too hot and not too cold.

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32
Q

Define exoplanet

A

A planet orbiting a star that is outside the solar system.

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33
Q

Define red shift

A

A spectrum shifted towards the longer wavelengths

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34
Q

Define blue shift

A

A spectrum shifted towards the shorter wavelengths.

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35
Q

Define Doppler effect

A

A change in the frequency of sound or light waves emitted from an object when it moves towards or away from an observer.

36
Q

Define arcsecond

A

1/3600th of a degree.

37
Q

Define parsec

A

The distance at which a star appears to move one arcsecond in six months (equal to 3.26 light years or 30 trillion km)

38
Q

Define baseline

A

A line between the two viewpoints used to calculate parallax angle (1AU is the baseline used for calculating star parallax)

39
Q

Define astronomical unit (AU)

A

The distance between Earth and the sun

40
Q

Define parallax

A

The effect by which the position of an object seems to change when it is observed from different locations

41
Q

Define light year

A

The distance that light travels in one year (about 10 trillion km)

42
Q

Define H-R diagram

A

A graph where the star luminosity is plotted against spectral type/temperature; Hertzsprung - Russel diagram

43
Q

Define galaxy

A

An independent groups of stars that are held together by gravity

44
Q

Define black hole

A

The extremely dense remnant of a massive star; a region in space where gravity is so strong that nothing, not even light, can escape.

45
Q

Define supernova

A

The explosion of a massive star

46
Q

Define white dwarf

A

A small, dense, dim star that has lost its outer layers and is at the end of its lifetime

47
Q

Define red giant

A

A very large, bright, cool star that has run out of hydrogen at its core

48
Q

Define main sequence

A

Stars that convert hydrogen into helium at their cores

49
Q

Define luminosity

A

The intrinsic brightness of a celestial object

50
Q

Define emission spectrum

A

A spectrum showing bright lines at wavelengths specific to emission from a substance

51
Q

Define absorption spectrum

A

A spectrum showing dark lines due to specific wavelengths that have been absorbed by a substance

52
Q

Define continuous spectrum

A

Continuous range of colours / wavelengths

53
Q

Define B-V Colour Index

A

The difference in brightness measured through blue and green filters, indicating the colour of a star

54
Q

Define spectral class

A

A group into which stars are classified based on their spectra / colour

55
Q

Define nuclear fusion

A

The process of joining two nuclei to produce energy

56
Q

Define radio telescope

A

A device that receives radio waves emitted by stars and other celestial objects

57
Q

Define optical telescope

A

A device that collects and focuses light from the visible spectrum to form an image

58
Q

Define heliocentric

A

A model of the solar system with the sun at the centre

59
Q

Define retrograde motion

A

Apparent backwards motion of a planet as seen from Earth

60
Q

Define geocentric

A

A model of the solar system with earth at the centre

61
Q

Define constellation

A

A group of stars as seen from Earth that appear to form a familiar shape

62
Q

What two points does Hubble’s law demonstrate?

A
  1. The universe is expanding from everywhere, not just earth

2. Using D=0 we can find the age of the universe

63
Q

What is the formula for Hubble’s law?

A

v = H0D

64
Q

How does a star’s spectra relate to how far away a star is?

A

The further a star’s spectra is shifted to red, the further away the star is

65
Q

How far away is the edge of the observable universe?

A

45 billion light years

66
Q

How was the cosmic microwave background discovered?

A

Two astronomers notices a buzzing and thought it was interference. They then investigated further and found it was the cosmic microwave background

67
Q

Why are the ‘dark ages’ called this?

A

All photons were scattered by plasma and so could not be observed

68
Q

What are three main pieces of evidence that support the big bang theory?

A
  1. Almost all galaxies are red shifted (moving away)
  2. Smaller elements not created inside stars
  3. Radiation left over (cosmic microwave background)
69
Q

How old is the universe?

A

13.7 billion years old

70
Q

What are some of the requirements an exoplanet must possess for it to be habitable by humans?

A
  • Made of rock
  • Enough oxygen in the atmosphere but not too much
  • In the ‘Goldilocks Zone’
71
Q

How far is the sun from the earth?

A

8 light minutes (150,000,000km)

72
Q

State the different shapes that galaxies can be

A

Elliptical, lenticular, spiral, barred spiral, irregular

73
Q

What luminosity is our sun on a H-R diagram?

A

1

74
Q

At what mass does a supernova have to be to become a black hole?

A

greater than 40 times the mass of our sun

75
Q

At what mass does a supernova have to be to become a neutron star?

A

Less than 40 times the mass of our sun

76
Q

TRUE or FALSE

The bigger a star, the longer its lifespan

A

False

The bigger a star, the quicker it burns through its fuel

77
Q

How big does a star have to be to become a red supergiant?

A

10x the mass of our sun

78
Q

Why do red giants increase in size?

A

The helium builds up in the core of the star and the region where fusion occurs becomes a shell around the core. This means the star will increase in size

79
Q

How many stars are estimated to be in their main sequence?

A

Roughly 90% of known stars

80
Q

Outline the main sequence within the life cycle of a star

A

Where stars spend majority of their life. Stage which they convert hydrogen into helium

81
Q

Explain why an ambulance siren changes to a slightly lower pitch as it passes you

A

When an ambulance passes someone, the sound waves become more stretched out, resulting in a lower pitch

82
Q

Explain why we cannot see photons emitted in the early stages of the universe

A

During the early stages of the universe all photons were scattered by plasma resulting in it being impossible for us to see photons before the epoch of recombination

83
Q

How do scientists know black holes exist without being able to see them?

A

Even though people can’t directly see a black hole, scientists can see the effect they have on nearby gas and stars

84
Q

Why can’t we see black holes?

A

Black holes have such a great amount of mass in a very small area, therefore, resulting in a gravitational force so strong that not even light can escape, making it impossible for the naked eye to see one

85
Q

What are the advantages and disadvantages of using a telescope in space?

A

The advantages are that the Earth’s atmosphere won’t be in the way, allowing the telescope to see into space more clearly. However, it does cost a lot more to do and becomes more difficult to repair

Year 10 MMS (6 decks)

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