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Science Semester Two > Astrophysics > Flashcards

Astrophysics Flashcards

1
Q

What is the order of the planets from the Sun?

A

What is the order of the planets from the Sun?

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2
Q

What is the structure of the solar system?

A

Sun is at the centre. Terrestrial and Jovian planets orbit.

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3
Q

Where is the asteroid belt located?

A

Between Mars and Jupiter

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4
Q

Where is the Kuiper Belt located?

A

Beyond Neptune

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5
Q

Where is the Oort Cloud?

A

Well beyond the Kuiper Belt

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6
Q

Why do planets orbit the sun?

A

Gravitational force of the Sun

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7
Q

What do planets do?

A

Orbit the sun in elliptical orbits in the same direction

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8
Q

What else does the solar system include?

A

Moons, asteroids, comets, dust, dwarf planets, kuiper blet objects, lots of empty space

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9
Q

What is our solar system apart of?

A

Milky Way

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10
Q

Where do stars orbit?

A

The centre of the galaxy due to the force of gravity

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11
Q

What is our view of the Milky Way?

A

Bright, milky band of light in the night sky

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12
Q

What does the night sky contain?

A

Planets, stars, galaxies

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13
Q

What group of galaxies does our galaxy belong to?

A

Local Group

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14
Q

How many galaxies are in the local group?

A

30

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15
Q

What is a constellation?

A

Group of stars that form a pattern in the sky.

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16
Q

What is the closest galaxy to us?

A

Andromeda Galaxy

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17
Q

Comparison between a constellation and galaxy

A
  1. one is real, one is made up
  2. different definitions
  3. similiarity = both to do with stars
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18
Q

What does star motion appear to be?

A

Stars and constellations appear to be moving across the night sky, as the Earth spins on its axis

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19
Q

What is a day?

A

The time required for Earth to rotate once on its axis

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20
Q

What is a year?

A

The time it takes Earth to complete a full rotation around the Sun.

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21
Q

What is a galaxy?

A

Huge collections of stars and gases, held together by gravity

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22
Q

What is the Universe?

A

All existing matter and space considered as a whole

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23
Q

What is a solar system?

A

Collection of planets and smaller bodies (moon, asteroids, meteroids, comets, etc) orbiting around a star

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24
Q

What is a planet?

A

Meets the criteria
- Orbit around a star
- Large enough to pull itself into a spherical shape
- Cleared the neighbourhood around its orbit

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25
Q

What is the number of galaxies in the Universe?

A

Around 500 billion

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26
Q

What is the distance between stars in a galaxy?

A

Around 5 light years

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27
Q

What is the average distance between galaxies?

A

Around 3.26 million light years

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28
Q

What criteria has Pluto not met to be a planet?

A

Cleared neighbourhood around its orbit

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29
Q

How many stars are in the Milky Way?

A

100 billion

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30
Q

What is the estimated amount of stars in the observable Universe?

A

2 x 10^22

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31
Q

What is an astronomical unit?

A

Distance between the Earth and the Sun. 150 million kilometres

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32
Q

What is a light year?

A

The distance light travels in one year. 9.5 x 10^15 kilometres

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33
Q

What is a parsec?

A

Distance to a star where parallax is one arc second

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34
Q

What is parallax?

A

The apparent change in position of an object when you look at it from different places

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35
Q

How is stellar parallax measured?

A

Measuring angular position of a star and then repeat the process six months later. Positions will be very different relative to a background of very distant stars

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36
Q

What is the largest galaxy in the Local Group?

A

Large Megellanic Cloud

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37
Q

What is the largest galaxy?

A

Andromeda

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38
Q

What is a geocentric model?

A

Earth is the center of the Universe . Planets and stars orbit in giant spherical shells

39
Q

What is the heliocentric model?

A

Sun is the center of the universe. Proposed by Copernicus

40
Q

What changes in technologies have allowed new scientific methods to be accepted?

A

Mathematical models, telescopes, measurements, cameras, radio telescopes

41
Q

What techniques have been used to allow new scientific methods to be accepted?

A

Watching and recording the night sky
Developing tools to take position measurements of stars and planets
Invention of the optical telescope, allowed to collect more data about more stars
Inventing technologies to learn more about properties of light coming from stars

42
Q

What is Hubble’s Law?

A

V = H0 x D.

V = speed of galaxy moving away from us. H0 = hubble constant (70km/s/Mpc). D = distance from the Earth

43
Q

What did Edwin Hubble discover?

A

That galaxies were moving away from Earth AND the farther away galaxies are, the faster they move away.

44
Q

When will the Milky Way and the Andromeda galaxy collide?

A

4 billion years

45
Q

What is the current view of the Universe?

A

Big Bang. No centre of the Universe

46
Q

What is the Big Bang theory?

A

The idea that all matter and energy in the universe began in an unimaginably dense state, and then space itself began expanding around 13.8 billion years ago

47
Q

What is a star?

A

Astronomical object consisting of a light-emitting ball of plasma held together by gravity. GASEOUS SPHERE OF LARGE MASS THAT PRODUCES ENERGY

48
Q

What is cosmic microwave background radiation?

A

Radiation left over from the Big Bang after the universe expanded and cooled. Most visible on the microwave section

49
Q

How is CMBR evidence for the Big Bang theory?

A

Hot objects emit light we can see. If the BB was true, must be some heat/radiation left over from its event. CMB should be detectable everywhere.

Initially, light could not move in the BB because it was so dense. About 300k years after the BB, it cooled and expanded. Light could travel whereever it wanted. As it travelled through space and expanded, light would be in microwave section

50
Q

How many galaxies are in the universe?

A

Around 500 billion

51
Q

What is redshift?

A

Stretching of the wavelength as it shifts to the red end of the spectrum, as it moves away from us

52
Q

What is the Doppler Effect?

A

Objects moving away from the observer stretch the wavelength to the red end of the spectrum. Objects moving towards the observer contract the wavelength to the blue end of the spectrum

53
Q

What is cosmological red shift?

A

Space itself is expanding, so the wavelengths are increasing

54
Q

How does red shift prove the Big Bang Theory?

A

Redshift only occurs when things are moving away. Light coming from more distant galaxies is shifted more towards the red end of the spectrum. Therefore, we can conclude that more distant objects are moving away from us at greater velocities

55
Q

What is the emission spectrum?

A

The specific wavelengths emitted by each element (each element is different)

56
Q

How is the amount of Helium in the Universe proving the Big Bang Theory?

A

Helium can only be made in very dense and hot environments. Today, the only environment where this is possible is a star. However, there is too much helium in the Universe to have only be made by stars. BB says that the early Universe would have been this conditions, so the Helium comes from here.

57
Q

How many metres is one light year?

A

9.5 x 10^15

58
Q

What is the closest star to our sun?

A

Proxima Centauri (4.24ly away)

59
Q

What is the formula for distance from Earth?

A

d (distance to the star in parsec) = 1/p (parallax angle of the star, in arc seconds)

60
Q

What are the limits to the parallax method?

A

From earth, up to 100pc because of distortions in the Earth’s atmosphere

61
Q

What is apparent magnitude?

A

how bright a star appears from earth

62
Q

What is absolute magnitude?

A

The actual brightness of a star, corrected for distance from Earth

63
Q

What does the colour of a star depend on?

A

Its surface temperature

64
Q

What is the Kelvin scale?

A

A temperature scale based upon absolute zero and calibrated in Celsius units. 0K = -273C

65
Q

What is the surface temperature of a star?

A

2000K - 20000K

66
Q

What is the HR diagram?

A

Hertzsprung-Russell diagram that compares a stars brightness to its temperature

67
Q

Why does the x-axis of an HR diagram appear back-to-front?

A

As the colour of light is determined by wavelength, it is shown in increasing wavelength. A higher wavelength = a lower temperature

68
Q

What does the vertical axis of the HR diagram show?

A

Brightness (negative numbers are the brightest)

69
Q

What is spectral class?

A

A classification system based on temperature

70
Q

What is the order of spectral class??

A

O B A F G K M (hot to cold)

71
Q

What spectral class is our Sun?

A

G class

72
Q

What is the trend of the HR diagram for main sequence stars?

A

Brighter it is, higher the temperature

73
Q

How are red giants classified?

A

Very large and bright, cool

74
Q

How are white dwarfs classified?

A

Hot, dim

75
Q

What is a main sequence star?

A

A star that is fusing hydrogen atoms to make helium in the core.

76
Q

What is one arc second equivalent to?

A

1/3600 degrees

77
Q

What is fusion?

A

A process in which the nuclei of two atoms combine to form a larger nucleus

78
Q

What is a gas nebula?

A

An enormous cloud of gas and dust that begins to collapse under the force of gravity. lots of matter collects at the centre until it gets hotter and more dense

79
Q

What is a red giant?

A

When a star runs out of hydrogen to fus, the core collpase because the force of gravity is more than the force of fusion. This causes the core to collapse and then be hot enough to contine fusion. The fusion can go up to Iron, and it expands.

80
Q

What is a white dwarf?

A

The remains of a star that ran out of fuel for nuclear fusion. Fluctuates in brightness and size. Outer layers float away as dust and gas, core remains but fusion stops. Core is still very hot but becomes very dim.

81
Q

What happens after a white dwarf?

A

Slowly cools until it becomes a brown/black dwarf

82
Q

What is a supernova?

A

Large mass stars that explode spectacularly, blowing away large quantities of gas and dust. Can outshine whole galaxy.

83
Q

What is a neutron star?

A

Collapsed core of a supernova. As dense as a nucleus (1tsp = 10 mill. tons)

84
Q

What is a black hole?

A

Collapsed core of a very latge star with a gravitational field so intense that no matter or radiation can escape.

85
Q

How could the Sun end Earth?

A

In 5 billion years, the Sun will burn hydrogen and it will run out to become a red giant. It will expand and potentially engulf the Earth

86
Q

How could the Earth end in terms of asteroids?

A

When asteroids (rocks objective over 10km in diameter) make it through the Earth’s atmosphere it is known as a meteorite. Can cause a lot of impact b/c smoke and dust can block sunlight and stop life on Earth.

87
Q

What is a meteroid?

A

Rocky object less than 10km in diameter

88
Q

What is a comet?

A

An object made of gas, ice, and dust

89
Q

What is a nebulae?

A

A giant cloud of dust and gas caused by a supernova

90
Q

What is the relationship between a supernova and the Earth’s death?

A

The radiation released could destroy the entire planet

91
Q

What is the Big Freeze?

A

Perfect density, everything continues to expand at a slower rate. Stars will run out of fuel and will evaporate, leaving the Universe free of matter and energy

92
Q

What is the Big Crunch?

A

Large density. If it is large enough, gravity will stop the Universe from expanding and pull everything back in.

93
Q

What is the Big Rip?

A

Low density, Gravity is too weak to stop the expansion of the Universe. Keeps expanding until the Universe is ripped apart

94
Q

What is the most likely death of the Universe?

A

Big Freez

Science Semester Two (2 decks)

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