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Astronomy > Section 2: Planetary Systems > Flashcards

Section 2: Planetary Systems Flashcards

0
Q

Name 3 dwarf planets

A

Ceres, Pluto, Eris

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1
Q

How many known moons?

A

160

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2
Q

Where’s the asteroid/main belt

A

Between Mars and Jupiter

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3
Q

Avg. size of asteroid?

A

10m-100km

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4
Q

Name 2 asteroids in the asteroid belt

A

Vesta (brightest), Pallas

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5
Q

What’s an asteroid

A

Small solid body

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6
Q

What’s a comet

A

Nuclei of ice, dust and rock; develops gaseous coma and tails when relatively close to the sun

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7
Q

What’s a centaur

A

Show similarities to both asteroids and comets

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8
Q

Where do centaurs orbit

A

Between Jupiter and Neptune

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9
Q

Name 3 centaurs

A

Chiron, Hidalgo, Asbolus

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10
Q

What’s a TNO

A

Trans-Neptunian object; orbits sun from beyond Neptune

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11
Q

International Astronomical Union (IAU) definition of a planet:

A
  1. Is in orbit round the sun
  2. Is large enough to be spherical
  3. Has “cleared its orbit” of other objects
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12
Q

1 AU

A

Mean distance from Earth to Sun = 150 million km

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13
Q

Features of Mercury

A

Heavily cratered; lava filled basins; appears similar to moon

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14
Q

Features of Venus

A

Spins backwards; similar size to Earth; clouds of sulphuric acid; surface pressure 90x on Earth; dense atmosphere containing carbon dioxide (prevents infra red escaping so v. hot)

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15
Q

Features of Mars

A

Iron rich rocks; seasonal ice caps; 450 km “Valles Marineris” canyon; highest volcano “Olympus Mons” in solar system; violent dust storms

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16
Q

Features of Jupiter

A

Equatorial bulge; dynamic wind system; anticyclone weather system “Great Red Spot”

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17
Q

Features of Saturn

A

Gas giant like Jupiter; rings

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18
Q

Where has info about solar system come from

A

Scientific instruments on unmanned space probes

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19
Q

Similarities in Neptune and Uranus

A

Similar size; gas giants; atmosphere of hydrogen, helium, methane, ammonia

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20
Q

Differences between Uranus and Neptune

A

Uranus spins on side, featureless surface; Neptune heavily marked incl. Great Dark Spot

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21
Q

Problems with manned space missions

A
  1. Space Adaptation Syndrome and other physiological problems (brittle bones; muscle fatigue)
  2. Communication delays
  3. Radiation from sun
  4. Psychological problems (fatigue, low motivation)
  5. Time
  6. Cost
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22
Q

Name Mars’ moons

A
  1. Deimos
  2. Phobos
    Irregular shape; ~10km; heavily cratered; half density of Mars; captured from Asteroid belt
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23
Q

Name Neptune’s moons and where they came from

A
  1. Triton - captured body from collision
  2. Dark Proteus - formed at same time
  3. Nereid - captured from Kuiper belt
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24
Q

Ecliptic

A

Plane of Earth’s orbit

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25
Q

Describe orbit of planets

A

Elliptical orbits slightly inclined to the ecliptic

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26
Q

Where do the planets appear to move through

A

Zodiacal band - a narrow region of sky

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27
Q

Inferior planets vs. superior planets

A

Inner vs. outer
Inferior = Mercury and Venus
Superior = Mars to Neptune

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28
Q

Direct motion

A

Planets generally move from West to East

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29
Q

Retrograde motion

A

Planets appear to move from East to West

  1. Planets orbit at diff. speeds
  2. Therefore we see planets from diff. viewpoints as we overtake or undertake them -> they appear to move backwards
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30
Q

Greatest elongation

A

Furthest from the sun in the sky - angle between planet-Earth and planet-sun is a right angle

Inferior planets

31
Q

Inferior conjunction

A

Inferior planets: angle of elongation is 0 -> lies directly between earth and sun

32
Q

Superior conjunction

A

Inferior planets: sun lies directly between earth and planet w. angle of elongation 0

33
Q

Conjunction

A

Superior planets: sun lies directly between earth and planet

34
Q

Transit

A

An inferior planet passes in front of the solar disc

35
Q

Occultation

A

An astronomical body passes behind another and is temporarily hidden from view

36
Q

Which planets atmosphere illustrates global warming

A

Venus: dense atmosphere of carbon dioxide; lower atmosphere 470 avg.

37
Q

Composition of planetary rings

A

Particles of ice, rock and dust

38
Q

Cometary orbits

A
  1. Much more elliptical and originate at vast distances from sun
  2. Can be either clockwise or anticlockwise
  3. Highly inclined to the ecliptic
39
Q

Location and nature of Kuiper belt

A

Thick disc shaped region of icy bodies; lies beyond Neptune at 30-50 AU from sun

40
Q

Location and nature of Oort Cloud

A

Spherical distribution of cometary nuclei; 50000 AU from sun

41
Q

Short period comets origins

A

Kuiper Belt

42
Q

Long period comet origins

A

Oort Cloud

43
Q

Evidence for Oort Cloud

A

From long period comets:

  1. Orbits either direction
  2. Highly inclined to ecliptic
  3. High percentage originate at 50000 AU from sun
44
Q

Coma of comet

A

Gas and dust up to 100000 km across

45
Q

Ion tail

A

Blue coloured; molecules of gas; ionised by solar wind; atoms de-excite and fluoresce

46
Q

Dust tail

A

Lighter colour, shorter broader than ion; radiation pressure pushes particles out of nucleus; shines by reflecting sun; curved as individual particles follow own orbit

47
Q

When do comet tails form

A

When relatively close to sun from high temp

48
Q

Nature of meteoroids

A

Small rocky irregular lumps of debris; micrometres to 10 m; orbit sun ~ 40 km/s

49
Q

Origin of meteoroids

A

Broken fragments of asteroids; impacts with surface of moon/mars

50
Q

Nature of Meteorites

A

Surviving part of meteoroid when it passes through earths atmosphere and lands on surface

51
Q

Meteor

A

Friction causes air around meteoroid to heat up when passing through earths atmosphere

52
Q

Fireballs

A

Meteors with magnitude of -3 or brighter

53
Q

Meteor showers

A

Earth passes through meteoroid stream - meteoroids originating from dust tails of comets

54
Q

Radiant

A

Where dust particles from meteor shower appear to diverge from

55
Q

Orbits of PHOs

A

Bring objects closer than 0.05 AU to us

56
Q

Consequences of PHO collisions with Earth

A
  1. Craters e.g. on moon
  2. Backwards rotation e.g. Venus
  3. Land destruction
  4. Tsunamis
  5. Global climatic change
57
Q

Copernicus discoveries

A
  1. Heliocentric model of solar system (i.e. Orbit sun)

2. Retrograde motion of Mars, Jupiter and Saturn

58
Q

Discoveries of Tycho

A
  1. Meticulously observed sky to work out actual positions of planets
  2. Tried to find evidence Earth orbited sun
59
Q

Discoveries of Kepler

A
  1. Used Tycho’s observations to formulate “Laws of Planetary Motion”
60
Q

Kepler’s second law

A

“An imaginary line from a planet to the sun sweeps out equal areas in equal intervals of time”

61
Q

Kepler’s first law

A

Planets move in elliptical orbit with sun at one focus

62
Q

Discoveries of Galileo

A
  1. Moon not spherical - contained craters and mountains
  2. Venus exhibited phases and it’s apparent size changed
  3. Four satellites orbit Jupiter: Callisto, Europa, Ganymede, Io
63
Q

Discovery of Uranus

A

1781 by William Herschel

- Looking at faint naked-eye stars with telescope

64
Q

Discovery of Ceres

A

1801 by Giuseppe Piazza

- Predicted there would be a planet between orbits of Mars and Jupiter

65
Q

Discovery of Neptune

A

1846 by Galle and D’Arrest

- Predicted planet beyond Uranus due to wobbles in its motion

66
Q

Discovery of Pluto

A

1930 by Clyde Tombaugh

- Uranus underwent further irregularities in orbit, predicted another planet lay beyond Uranus

67
Q

Exoplanet

A

Planet not in solar system

68
Q

Techniques for discovering exoplanets

A
  1. Astrometry - star wobbles in small orbit pulled by large exoplanet
  2. Transit method - exoplanets move across disc of host star cause drop in brightness
  3. Radial velocity method - wobbling of star causes wavelengths of star to be shifted regularly detected by spectroscopy
69
Q

Difficulties with current methods for discovery of exoplanets

A

Can only discover large planets close to sun - “hot Jupiters”
Atmospheric turbulence can interfere with measurements

70
Q

Essential chemicals for life

A
  1. Carbon - create organic compounds

2. Liquid water - solvent and transport mechanism for nutrients, photosynthesis, hydrolysis

71
Q

Origin of water on Earth

A
  1. Out gassing of hydrogen and oxygen from volcanoes combining to steam condensing to water
  2. Deposited by ice containing comets striking Earth
72
Q

Analysis of water by Rosetta probe

A

Drop small lander onto comet; see if it has same relative abundance of isotopes as water on Earth

73
Q

“Goldilocks zone”

A

Also known as habitable zone, range of distances from star where temperature allows liquid water to exist

74
Q

Drake equation

A

Estimates number of civilisations able to communicate with us
Factors:
1. Number of stars in galaxy
2. Fraction of stars with planetary systems
3. Number of planets capable of sustaining life
4. Fraction of life forms that are intelligent
5. Fraction of these that can and wish to communicate

75
Q

Methods of obtaining evidence for life

A
  1. Space probes
  2. Spectral analysis of atmospheres above rocky exoplanets
  3. Analysis of radio waves possibly from extra-terrestrial intelligent life forms

Astronomy (4 decks)

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