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Astronomy > Lectures 7-12 > Flashcards

Lectures 7-12 Flashcards

1
Q

What does the part of the Solary Sytem occupied by planets look like?

A

flattened, everything in almost the same plane

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2
Q

What is the shape of orbits of dwarf planets?

A

very elliptical

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3
Q

What is the shape of the orbit of the 8 major planets?

A

nearly circular, all orbit in same direction and nearly on the same plane

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4
Q

Name the planets in order.

A

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune,

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5
Q

Properties of the Sun

A
  • over 99.9% of solar system’s mass

- mostly H and He gas (plasma)

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6
Q

Properties of Mercury

A
  • made of metal and rock
  • large iron core
  • desolate, cratered, cliffs
  • very hot and very cold 425C day -170C night
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7
Q

Properties of Venus

A
  • almost the same size as Earth
  • surface hidden by clouds
  • extreme greenhouse effect
  • even hotter than Mercury 470C day and night
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8
Q

Properties of Mars

A
  • looks like Earth

- polar caps, canyonns…

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9
Q

Properties of Jupiter

A
  • much farther from Sun than the inner planets
  • mostly H/He
  • no solid surface
  • 300x the mass of Earth
  • many moons, rings
  • Galilean moons= Io,Europa,Ganymede,Calisto
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10
Q

Properties of Saturn

A
  • giant, gaseous like Jupiter
  • rings= not solid made of small chunks of ice and rock each orbiting like a small moon
  • many moons (incl. Titan)
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11
Q

Properties of Uranus

A
  • smaller than Jupiter and Saturn, still much larger than Earth
  • H/He gas and hydrogen compounds (H2O,NH3,CH4)
  • extreme axis tilt
  • moons and rings
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12
Q

Properties of Neptune

A

-similar to Uranus but not the axis tilt

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13
Q

Properties of Pluto and other dwarf planets

A
  • much smaller than major planets, icy-comet like composition
  • pluto has a moon Charon= almost the same size as Pluto
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14
Q

Properties of terrestrial planets

A
  • smaller size and mass
  • higher average density
  • made mostly of rocks and metals
  • solid surface
  • few if any moons and no rings
  • closer to the Sun and together with warmer surfaces
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15
Q

Properties of jovian planets

A
  • larger size and mass
  • lower average density
  • made mostly of H He and hydrogen compounds
  • no solid surface
  • rings and many moons
  • farther from the Sun and from each other with cooler temperature cloud tops
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16
Q

How do you measure the distance to Venus?

A

Measure apparent position of Venus on Sun from two locations on Earth.

  • use trigonometry to determine Venus’ distance from the distance between the two locations on Earth
  • that’s how we measured the AU
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17
Q

What is a transit of a planet?

A

When planet passes between the Earth and the Sun and you can see it on the Sun.

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18
Q

What is a flyby mission?

A 
-fly by a planet just once, captured by gravity and sling shot further
Voyager 1 (1977)125 AU away -at the edge of the solar system 19 billion km 
Voyager 2 (1977) 101 AU, 15 billion km away
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19
Q

Describe the nebular theory

A

-Solar system formed from the gravitational collapse of a giant interstellar gas cloud

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20
Q

What are the exceptions to the usual pattern in the Solar System?

A
  • Uranus’ tilted axis
  • Earth’s large moon
  • Venus’ rotation
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21
Q

What is meant by galactic recycling?

A

Elements that formed planets were made in stars and then recycled through interstellar space

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22
Q

What caused the orderly patterns of motion in our solar system?

A

Conservation of angular momentum.-increasing speed of rotation with contraction
Flattening-collisions between particles in the cloud

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23
Q

Why are there two major types of planets?

A
  • as cloud contracting it heats up, inner part hotter than outer, rock can be solid at higher temp than ice
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24
Q

What is the frost line?

A

A line inside which too hot for hydrogen compounds to form ices,
outside= cold enough to form ices

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25
Q

How did the terrestrial planets form?

A
  • small particles of rock and metal inside the frost line
  • planetesimals built up as the particles collided
  • gravity eventually assembled these into terrestrial planets= accretion
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26
Q

Explain accretion of planetesimals.

A

Gravity draws them together, many small ones collected into bigger objects, eventually planets.

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27
Q

How did the jovian planets form?

A
  • ice formed small particles outside the frost line
  • larger planetesimals and planets able to form
  • gravity of rock and ice in jovian planets draws in H and He gases, so that’s why they’re bigger-gas doesn’t take as much gravity.
  • each jovian planet is like a miniature solar system
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28
Q

What is the composition of the Solar system?

A

98% H and He gas don’t condense in the nebula

  1. 4% hydrogen compounds (H2O, methaneCH4,ammonia NH3) -condense at 150K
  2. 4% rock-various mineral-condense at 500-1300K
  3. 2% Metal-iron,nickel,aluminum condense at 1000-1600K
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29
Q

How come there isn’t any H He gas floating around anymore?

A

Combination of photons and solar wind blew them away.

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30
Q

How did Sun’s rotation change over time with regard to the nebular theory?

A
  • the young Sun rotated much faster than now

- friction between solar magnetic field and solar wind probably slowed it down.

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31
Q

What are asteroids and comets?

A

The leftover junk from the planetary accretion process.

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32
Q

Where are the rocky asteroids in the solar system?

A

Inside the frost line.

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33
Q

Where are the icy comets in the solar system?

A

Outside the frost line.

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34
Q

Why are many planets cratered?

A

Leftover planetesimals bombarded other objects in the late stages of solar formation.

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35
Q

Where does the water on Earth come from?

A

Probably came from icy planetesimals.

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36
Q

What is a possible explanation for some of the unusual moons in the Solar system?

A

They may be captured moons, unusual shape because not massive enough to be round.

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37
Q

How did we get our Moon?

A
  • Mars sized planetesimal crashes into the Earth
  • Hours later, Earth molten and rotating rapidly, lot of debris around, some goes on Earth surface and some will accrete to create the Moon
  • 1000 yrs later accretion of the Moon done and little debris left
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38
Q

What explains the odd rotation of Uranus and Venus?

A

-giant impacts

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39
Q

How old is the Solar System? and how do we know?

A
  • finding oldest rocks, radioactive dating is the most useful, oldest rocks in Greenland, WA , moon rocks and meteorites-
  • about 4.54 billion years old rocks
  • so planets probably formed at 4.5 billion yrs ago
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40
Q

Explain the basic idea of radioactive dating?

A
  • all elements in a rock formed at the same time
  • no new parent or daughter formed at later times
  • the half life is known
  • process: count the number of parent and daughter atoms
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41
Q

What is half-life?

A

Some isotopes decay into other nuclei, a half life is the time for half the nuclei in a substance to decay

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42
Q

What is the Earth’s interior?

A

Core- highest density: nickel and iron
Mantel-moderate density: silicon, oxygen etc.
Crust- lowest density: granite, basalt etc.

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43
Q

How do terrestrial planets differentiate?

A
  • Gravity pulls high-density material to the centre
  • Lower density material rises to surface
  • Material ends up separated by density
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44
Q

What is the litosphere?

A
  • a planet’s outer layer of cool,rigid rock
  • it floats on the warmer, softer rock that lies beneath
  • crust and part of mantle
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45
Q

What do P waves do?

A

P waves push matter back and forth

46
Q

What do S waves do?

A

S waves shake matter side to side

47
Q

How do we know what’s inside the Earth?

A

-P waves go through the Earth’s core but S waves don’t so we Earth’s core must have a liquid layer.

48
Q

Why is the Earth’s core hot?

A
  • in the beginning: accretion and differentiation when planets were young
  • today: radioactive decay is most important source today
49
Q

How does a planet’s interior cool?

A
  • convection: transports heat as hot material rises and cool material falls
  • conduction: transfers heat from hot material to cool material
  • radiation:sends energy into space
50
Q

Role of size in planet cooling?

A

Smaller worlds cool off faster and harden earlier

-the Moon and Mercury are now geologically dead

51
Q

Surface area to volume ratio and heat.

A
  • heat content depends on volume

- loss of heat through radiation depends on surface area

52
Q

Why do some planets have magnetic fields?

A
  • Magnetic fields are created by motions of charged particles
  • A planet can have a magnetic fields if charged particles are moving inside it
53
Q

Earth’s magnetic field and requirements for its existence?

A
  • molten electrically conducting interior
  • convection
  • moderately rapid rotation
54
Q

Name the 4 main processes that shape terrestrial planets’ surfaces.

A
  • Impact cratering: asteroids and comets
  • Volcanism: eruption of molten rock onto surface
  • Tectonics: disruption of a planet’s surface by internal stresses
  • Erosion: surface changes made by wind, water or ice
55
Q

Impact cratering-

A

most happened soon after the solar system formed

  • craters ate about 10x wider than the objects that made them
  • more small ones than big ones
56
Q

Volcanism-

A
  • volcanism happens when molten rock (magma) finds a path through litosphere to the surface
  • molten rock is called lava after it reaches the surface
57
Q

How does lava influence the surface? In terms of how thick it is.

A
  • runny lava- makes flat lava plains
  • slightly thicker lava males broad shield volcanoes
  • thick lava makes steep stratovolcanoes
58
Q

How does volcanism contribute to the atmosphere?

A

Outgassing, releases gases from Earth’s interior to the atmosphere.

59
Q

Explain tectonics?

A
  • convection of the mantle creates stresses in the crust= tectonic forces
  • compression of crust= mountain ranges
  • valley forms where crust pulled apart
60
Q

What drives erosion?

A 
weather driven-
glaciers
rivers
wind
rain
61
Q

How do craters reveal a surface’s geological age?

A

Most cratering happened in the first billion years.
-more craters= older
younger regions= lava flooded

62
Q

Why do larger planets (terrestrial) have more volcanism and tectonics?

A

They remain warmer inside for longer.

63
Q

Why do larger planets have more erosion?

A

Because their gravity retains an atmosphere.

64
Q

How does the distance from the Sun affect the terrestrial planets’ climate and erosion?

A
  • closer to the Sun too hot for rain, snow and ice= less erosion
  • hot planets have more difficulty maintaining an atmosphere (kinetic energy)
  • planets far from the Sun too cold for rain, limiting erosion
  • planets with liquid water have the most erosion
65
Q

Effect of planet rotation on weather, erosion and magnetic field?

A
  • slower rotation= less weather, less erosion,weak magnetic field
  • faster rotation= more weather, more erosion, stronger magnetic field
66
Q

Why does Mercury have long steep cliffs?

A

It shrunk and some of the crust was forced to slide under others.

67
Q

What is Olympus Mons?

A

volcano on Mars, the largest in the solar sytem

68
Q

What is the origin of valleys on Mars?

A

Tectonics

69
Q

Did water flow on Mars?

A

Likely. Erosion that looks to have been caused by water on the surface.

  • there are rocks on Mars that seem to have formed in water
  • there is still lot of hydrogen, normally it escapes fast so there must be source of it somewhere on Mars
70
Q

How do you explain the difference in cratering densities on the Moon?

A

-younger regions flooded by lava- no craters= maria

71
Q

Is there water on the Moon?

A

Most certainly.

72
Q

What does the surface of Venus look like?

A

Must use radar due to clouds.
Impact craters but fewer than the Moon, Mercury and Mars
-shield volcanoes
-fractured and contorted surface= tectonic stress but not recently

73
Q

Why do you not want to live in California?

A

The San Andreas Fault= earthquakes every 150 years, last one in 1857

74
Q

How thick is the Earth’s atmosphere?

A

10 km. (mostly N2 and 02)

75
Q

What are the effects of an atmosphere on a planet?

A
  • creates pressure determining if liquid water can be on the surface
  • absorbs and scatters light
  • creates wind, weather and climate
  • interacts with the solar wind to create a magnetosphere
  • can make surface warmer due to greenhouse effect
76
Q

What is albedo?

A

Planet’s reflectivity, the fraction of incoming sunlight it reflects.
low albedo=absorb more sunlight, leading to hotter temperatures

77
Q

What is Greenhouse effect?

A
  • visible light passes through the atmosphere and warms the surface
  • the atmosphere absorbs infrared light from the surface, trapping heat
78
Q

What would be the Earth’s average temperature if there was no greenhouse effect?

A
  • 16 now average 15

- 31C difference

79
Q

How much colder would Venus be without the Greenhouse effect?

A

510C colder

80
Q

How is Earth heated?

A

from below the surface

  • light of different energies from the Sun
  • mostly visible light reaches the surface
81
Q

What is ionisation in the atmosphere?

A

removal of an electron (UV, X-Ray)

82
Q

What is dissociation in the atmosphere?

A

destruction of a molecule (UV, X-Ray)

83
Q

What is scattering in the atmosphere?

A

change in photon’s direction (optical)

84
Q

What is meant by absorption in the atmosphere?

A

Photon’s energy is being absorbed (IR).

85
Q

What is the troposphere?

A
  • closest to earth

- lowest layer warmed by IR light from Earth’s surface

86
Q

What is the Stratosphere?

A

above troposphere, warmed by UV from the Sun

-has ozone layer in it

87
Q

What is the Thermosphere?

A

-above stratosphere, warmed by X-Ray and UV from Sun

88
Q

What is Exosphere?

A

-above thermosphere, fades into space =100km =space

89
Q

Describe how far does light of different energies get in the atmosphere?

A

Least- X ray, then UV and most visible

90
Q

Why is the sky blue?

A

-Atmosphere scatters blue light from the Sun making it appear come from different directions.
Sunsets are red because red light scatters less.

91
Q

Why is the magnetic field important for us on Earth?

A

It protects us from the charged particles streaming from the Sun (solar wind).

92
Q

How is aurora generated?

A

Charged particles from solar wind energise the upper atmosphere near magnetic poles.

93
Q

What is weather?

A

-the daily variations in wind, clouds, temperature, and pressure; local and hard to predict

94
Q

What is the climate?

A

-the long-term average of weather; long-term stability of climate depends on global conditions and is more predictable

95
Q

What produces circulation cells?

A

The hot/cold of the equator and the poles plus the Earth’s rotation, if without rotation= just two cells, with= 6

96
Q

What is solar brightening?

A

The Sun gradually grows brighter with time, increasing the amount of sunlight warming the planets.

97
Q

How does the changing of axis tilt affect weather?

A
  • seasons
  • larger tilt= more extreme seasons
  • smaller= keeps polar regions colder
98
Q

Does the tilt of the Earth’s axis change?

A

-yes
-small gravitational tugs from other bodies in solar system cause the tilt to vary from 22 to 25 degrees.
(normally 23.5)

99
Q

How can Earth’s climate change?

A
  • sun brightening
  • axis tilt
  • change in reflectivity
  • change in greenhouse gases
100
Q

What are the 3 major ways in which a planet can obtain an atmosphere?

A
  • Outgassing from volcanoes
  • Evaporation of surface liquid; sublimation of ice
  • impacts of particles and photons
101
Q

Can atoms escape the gravity of a planet when obtained enough thermal energy?

A

Yes.

-more thermal energy= more kinetic energy= achieve escape velocity

102
Q

Do the Moon and Mercury have any atmosphere?

A
  • extremely thin, gas comes from impacts that eject surface atoms
  • functionally NO!
103
Q

Are there seasons on Mars?

A

Yes, because of the ellipticity of Mars’ orbit= more extreme in southern hemisphere.

104
Q

Describe the polar caps on Mars.

A
  • residual ice of the south polar cap remains during summer= primarily water ice.
  • carbon dioxide ice of polar cap sublimates as summer approaches and condenses at the opposite pole
105
Q

How has the climate on Mars changed in history?

A
  • hasn’t had surface water for 3 billion years
  • Greenhouse effect probably kept surface warmer before
  • somehow Mars lost its atmosphere
106
Q

Describe the atmosphere on Venus.

A
  • thick, CO2 atmosphere with surface pressure 90x that of Earth= strong greenhouse effect
  • slow rotation produces very weak Coriolis effect and little weather
107
Q

What is runaway greenhouse effect?

A

If Earth placed in Venus’ place= more sunlight= more evaporation= more greenhouse gas= more heat etc. till we’re like Venus.

108
Q

Why is Earth’s atmosphere so different to all the other terrestrial planets?

A
  • it’s in the habitable zone, can have liquid water
  • life changed it, decrease in CO2, increase in O2
  • O2 led to ozone layer (ozone O3) when oxygen smashed by UV)
  • Moon= a stable orbit
109
Q

Why does Earth’s climate stay stable?

A

Earth’s thermostat, cooling allows CO2 to build up in the atmosphere and heating causes rain to reduce CO2 in the atmosphere

110
Q

How can long term climate change look like + causes.

A
  • changes in axis tilt= ice age
  • widespread ice= higher reflectivity= lower temperature
  • CO2 from outgassing would built up if oceans frozen and eventually raise global temperatures again

Astronomy (6 decks)

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