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Astronomy > Section 1: Earth, Moon And Sun > Flashcards

Section 1: Earth, Moon And Sun Flashcards

0
Q

Shape of Earth

A

Oblate spheroid

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1
Q

Features of Earth

A
  1. Atmosphere - mainly oxygen and nitrogen
  2. Liquid water ~ 70% of surface
  3. Life
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2
Q

Diameter of Earth

A

13000 km

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3
Q

Evidence Earth is spherical

A
  1. Ships disappear over horizon
  2. Satellites orbit Earth
  3. Earths shadow curves during partial lunar eclipse
  4. Images of Earth from space
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4
Q

Rotation period of Earth

A

23 hours 56 minutes

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5
Q

Time for Earth to rotate 1 degree

A

4 minutes

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6
Q

Equator

A

Divides Earth into Northern/Southern hemispheres

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7
Q

Tropics

A

Latitude of 23.5 degrees
Cancer = N
Capricorn = S

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8
Q

Latitude

A

Parallel to equator

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9
Q

Longitude

A

Perpendicular to equator, converge at poles

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10
Q

Poles

A

Top and bottom of axis Earth rotates on

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11
Q

Meridian

A

Imaginary North-South line running through that point (like longitude)

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12
Q

Horizon

A

Tangent to Earths surface from observer

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13
Q

Zenith

A

Directly above observer

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14
Q

Causes of light pollution

A
  1. Urban street lamps
  2. Commercial and sports floodlights
  3. Domestic and industrial security lamps
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15
Q

Problems with light pollution

A

Causes orange background haze which prevents many faint stars, nebulae and the Milky Way from being observed

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16
Q

How Eratosthenes calculated Earth’s circumference

A
  1. On summer solstice Syene on Tropic of Cancer sun lay directly overhead so no shadows were cast
  2. Same time at Alexandria measurement of sun showed it 7 degrees from zenith = 1/50 of a circle
  3. Using distance between these places, calculated circumference = 50xdist
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17
Q

Make up of Earths atmosphere

A

78% nitrogen; 21% oxygen; 1% argon; 0.04% CO2; 1% water vapour

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18
Q

Benefits of Earths atmosphere

A
  1. Absorbs harmful UV radiation
  2. Absorbs energetic X/gamma rays
  3. Regulates temperature
  4. Provides oxygen to breathe
  5. Partly protects us from meteoroids
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19
Q

Drawbacks of atmosphere

A
  1. Causes light to refract, restricting resolution of images
  2. Selective scattering of short blue wavelengths of light causes sky to appear blue so can’t make observations during the day
  3. Absorption/reflection of most e.m. radiation so UV/X ray observatories etc. must be placed on Earth orbiting satellites
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20
Q

Reflecting telescopes

A

A curved mirror collects the light

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21
Q

Refracting telescopes

A

Glass convex lens collects the light and brings it to a focus

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22
Q

What’s an objective

A

Lens or mirror of telescope

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23
Q

Why are large telescopes reflectors

A

Large mirrors can be manufactured to higher precision than lenses and are much lighter

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24
Q

Van Allen belts

A

2 donut shaped rings of high energy particles held in place by Earths magnetic field

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25
Q

Inner Van Allen belt

A

High energy protons from collisions between cosmic rays and atoms in atmosphere

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26
Q

Outer Van Allen belt

A

Electrons and other charged particles emitted by sun during increased solar activity

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27
Q

Discovery of Van Allen belts

A

Inner: Jan 1958 using Geiger counter on board “Explorer 1” satellite
Outer: Dec 1958 similar instruments on board space probe “Pioneer 3”

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28
Q

Draw moon map

A 
Include: 
Sea of tranquility
Ocean of Storms
Sea of Crises
Tycho, Copernicus and Kepler craters
Apennines mountain range
29
Q

Moons diameter

A

3500 km

30
Q

Moons distance from Earth

A

380000 km

31
Q

Moons rotational period and orbital period

A

27.3 days

32
Q

Why is far side of moon not vis. from Earth

A

Rotational period = orbital period

33
Q

How do astronomers know appearance of far side of moon

A

Apollo space program to land astronauts on the moon

34
Q

Appearance of far side of moon

A

Devoid of seas
Entirely mountainous
Heavily cratered

35
Q

Appearance of near side of moon

A

Dark grey “seas”
Lighter grey mountainous highlands (older)
Rilles - trenches caused by lava flows
Wrinkle ridges - buckling from cooling lava contracting

36
Q

Formation of moon

A

Giant Impact Hypothesis
Relatively young Earth struck by Theia (Mars-sized)
During impact Theia and Earth’s outer layers merged and debris was thrown into Earths orbit = moon

37
Q

Evidence for giant impact hypothesis

A
  1. Relative abundances of isotopes of oxygen same as on Earth
  2. Lack of water suggests vaporisation during collision
  3. KREEP rocks suggests ocean of hot cooling magma would have surrounded the moon
38
Q

Why doesn’t moon have atmosphere

A

Gravity too low

39
Q

ALSEPs

A

Apollo space programme and its experimental packages

(1. Laser ranging retroreflector to determine earth moon distance)
2. Structure of moons interior
3. Composition and pressure of lunar atmosphere
4. Presence of micrometeorites ejected by meteorite impacts

40
Q

Purpose of Apollo space program

A

Collection of lunar soil and rock for analysis
Deployment of scientific experiments on moons surface
Winning space race against Soviet Union to land a human on the moon

41
Q

Sun’s diameter

A

1.4 million km

42
Q

Suns distance from Earth

A

150 million km

43
Q

Temperature of suns photosphere

A

5800K

44
Q

Temperature of suns corona

A

2 million K

45
Q

Observing sun safely

A

Telescope with H alpha filter

Indirect projection to reduce brightness

46
Q

Suns rotation period

A

25 days at equator

36 days at pole

47
Q

Sunspots and structure

A

Cooler areas of photosphere corresponding to strong localised magnetic fields
Umbra - central darker region 2000K cooler than photosphere
Penumbra - lighter surrounding area 200K cooler than photosphere

48
Q

How can astronomers use sunspots to determine suns rotation period

A

By following apparent motion of sunspots across disc can deduce that sun does not rotate as a solid body

49
Q

Butterfly diagram

A

Latitude/time chart for sunspots

50
Q

Solar wind

A

Steady stream of charged particles from suns corona
Slow solar wind - high temp of corona gives particles enough k.e. to escape suns gravity 400km/s
Fast solar wind - coronal holes (open mag. field lines) allow particles to escape at 850km/s

51
Q

Chromosphere

A

2000km thick

Reddish pink ring before totality in solar eclipse

52
Q

Corona

A

Region of ionised gas

2 million K

53
Q

Why do sun and moon appear same size in sky

A

Sun 400x larger but also 400x further away so appears 400x smaller i.e. equal to size of moon

54
Q

Period of lunar phase cycle

A

29.5 days

55
Q

Describe lunar cycle

A

New moon
Waxes -> crescent; gibbous; full moon
Wanes -> gibbous; decrescent; new moon

56
Q

Total solar eclipse appearance

A

Light from suns photosphere obscured
Dark umbra shadow cast on Earth
Sky darkens so some brighter stars can be seen
Suns corona is visible
Baily’s beads - suns rays shine through valleys on the moon

57
Q

Partial solar eclipse appearance

A

Sun appears to have circular bite missing from it

Earth is cast in penumbra shadow

58
Q

Total lunar eclipse

A

Moon appears red/copper as light from sun passes through Earths atmosphere and blue light is scattered

59
Q

Partial lunar eclipse

A

Curved shadow of Earth can be seen on full moon

60
Q

Duration and phase of moon in solar eclipse

A

Few minutes

New moon

61
Q

Duration and phase of moon in lunar eclipse

A

30 mins - 1 hour

Full moon

62
Q

Why are eclipses rare

A

Moons orbit tilted slightly to ecliptic so sometimes appears above or below sun in the sky

63
Q

Solar day

A

24 hours

Time taken for successive crossings of the sun across the observers meridian

64
Q

Sidereal day

A

23 h 56 min

Time taken for successive crossings of a given star across an observers meridian

65
Q

Why are sidereal and solar days different lengths

A

During 1 complete Earth rotation it has also moved in its orbit around the sun so an extra 4 minutes must be allowed for the sun to return to the same position in the sky

66
Q

Determining time using sundial

A

Sundial measures apparent solar time but a clock reads mean solar time/GMT
Take into account longitude and EOT to determine GMT from sundial

67
Q

EOT

A

Apparent solar time - mean solar time

68
Q

Cause of aurorae

A

Electrons from solar wind accelerated to high speeds in Earth’s magnetic field, exciting molecules of oxygen and nitrogen which give out light at characteristic wavelengths

69
Q

Appearance of aurorae and where they can be observed

A

Green yellow and red whirlpools of light in the sky

Observed from high latitudes

Astronomy (4 decks)

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