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gcse astronomy > topic 11 > Flashcards

topic 11 Flashcards

1
Q

what is the name of the dwarf planet not located in the kupier belt and where is it located?

A

ceres - located in asteroid belt

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2
Q

what does eccentricity of a comet tell you?

A

how squashed the ellipse is. 1 is a circle and going down is more squashed

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3
Q

what is a planet (3)

A
  • orbits a star
  • its gravity is strong enough to pull it into a sphere
  • It has cleared it’s region of space of smaller bodies
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4
Q

what are the two tails of a comet?

A

ion and dust

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5
Q

explain the ion tail of a comet

A

trail of plasma streaming back from solar wind - points in exactly opposite direction of sun

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6
Q

explain the nucleus of a comet

A

solid comet core, ma be hidden by coma

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7
Q

explain the coma of a comet

A

vapour cloud surrounding the nucleus

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8
Q

explain the hydrogen envelope of a comet

A

invisible, irregular cloud surrounding the coma

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9
Q

explain the dust tail of a comet

A

prominent trail of dust and gases that curves backwards

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10
Q

describe short period comets (3)

A
  • likely origin in kupier belt
  • orbit < 200 y
  • periods in hundreds of years
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11
Q

describe long period comets (3)

A
  • likely origin in oort cloud
  • orbit > 200y
  • periods in thousands of years
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12
Q

what are comets orbits often like and what does this suggest? (4)

A

1) very eccentric (not circular)
2) very inclined to the ecliptic
3) retrograde

^ these suggest an origin outside of the solar system

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13
Q

describe the kupier belt (3)

A
  • outer solar system, from orbit of neptune onwards
  • 30 - 50 AU
  • similar to asteroid belt, but mostly comets, centaurs, and dward planets
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14
Q

describe the heliosphere(2)

A
  • upto a distance of 80-100 au in the direction the sun moves through interstellar space, many times that distance in the opposite direction
  • termination shock: radiation from the sun reaching maximum distance around due to gravity
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15
Q

describe the oort cloud(3)

A
  • in interstellar space (space between stars)
  • 2000 au to 200k au
  • mostly consisting of comets, with 1-2 % asteriods
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16
Q

describe mercury(3)

A
  • no atmosphere
  • appearance similar to our moon
  • not much bigger than our moon
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17
Q

describe venus(4)

A
  • thick carbon dioxide atmosphere
  • the hottest planet in the solar system
  • similar size to earth
  • a day is longer than a year
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18
Q

describe earth(2)

A
  • the only planet with liquid water
  • only place in the universe (THAT WE KNOW) supports life
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19
Q

describe mars(4)

A
  • evidence of water eriosion on the surface
  • polar ice caps
  • very thin atmosphere of mostly carbon dioxide
  • 2 small moons, probably captured asteroids
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20
Q

describe jupiter(4)

A
  • the largest planet
  • a gas giant, mostly hydrogen and helium
  • giant red spot is a storm that has lasted 400 years
  • more than 75 moons-
    the 4 galilean moons are historically important
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21
Q

describe saturn(3)

A
  • another gas giant
  • prominent ring system first seen by galileo - the remains of a moon that broke into pieces
  • at least 53 moons including titan (only jupiter’s moon ganymede is bigger)
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22
Q

describe uranus(4)

A
  • discovered in 1781 by william herschel
  • mostly icy water, methane and ammonia with a hydrogen helium outer layers
  • rotates on its side
  • at least 27 moons, many named after shakespeare characters
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23
Q

describe neptune(4)

A
  • another icy giant very similar to uranus
  • its existence was predicted due to observed gravitational effects on neptune
  • 14 moons including triton
  • its retrograde orbit suggests that is was probably captured from the kupier belt
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24
Q

what is an astronomical unit?

A

the mean distance between the earth and sun

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25
Q

what’s the conversion for au to km?

A

1AU = 1.5 x 10^8km

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26
Q

when converting, which unit goes on the denominator?

A

the unit you start out with (ie - the unit you DON’T want)

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27
Q

what is a meteoroid (definition not differenciation)

A

meteoroids are smaller pieces of rock in space between 1m in diameter to tiny grains

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28
Q

what is a meteoroid

A

a piece of rock in space

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29
Q

what is a meteor

A

enters the earth’s atmosphere (a shooting star)

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30
Q

what is a meteorite

A

survives atmospheric heating and hits the surface

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31
Q

how are meteoroids formed

A

by collision of asteroids or other bodies

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32
Q

describe the composition of a meteoroid

A

crumbly rocky or metallic debris, mostly silcates, some iron and niken

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33
Q

what can the composition of a meteoroid tell us?

A

where it came from

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34
Q

where is a widmanstaten pattern found

A

in nickel-iron meteorites

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35
Q

how is a widmanstaten pattern formed

A

produced by exceptionably slow cooling over millions of years

36
Q

what is the ecliptic?

A

the plane around the sun where all the planets orbit -23,5* away from the celestial equator

37
Q

how did halley use the transit of venus

A

halley used the transit of venus to determine the value of 1AU

38
Q

what is transit of venus

A

when venus is seen to pass over the face of the sun

39
Q

how do we calculate the orbital radius of everything in the solar system (2)

A

if we know the distance between the two observers on earth and the angle between the two observed transits we can work out 1AU

we can then use keplers 3rd law to calculate the orbital radius of everything in the solar system

40
Q

what is the first theory for water on earth?

A

the water and rock was all accreted together to form the proto-earth, so the water was always there

41
Q

what is the second theory for water on earth

A

smaller icy bodies may have been dislodged from their orbits and brought to earth after its formation

42
Q

what is the third theory for water on earth

A

theia (giant impact hypothesis for formation of mooon) brought water from the outer solar sustem when it collided to form the earth and moon

43
Q

TRUE or FALSE there isn’t evidence to support all three of the water on earth theories

A

FALSE - there in fact IS evidence to support ALL THREE of the water on earth theories

44
Q

describe human eye

A

around only 3mm in diameter and can only detect a few photons

45
Q

describe the drawbacks of human eye

A

a body with too small a SOLID ANGLE(how big something looks in the sky) in our field of view, and which is too dim, will not be visible

our eyes have limited sensitivity to light, especially when it is dark

46
Q

why can we see more with a telescope than the naked eye

A

we can see much more with a telescope than we can with the naked eye - this is because a telescope has a much larger aperture than our pupil so much more light enters it.

47
Q

describe objective lens(3)

A
  • collects light
  • more light can be captured using a
    telescope with a larger aperture than our pupils
  • lenses can be used to capture even more light
48
Q

what are the two types of telescope

A

refracting and reflecting

49
Q

what differentiates the two types of telescope

A

refracting: contains lenses

reflecting:contains mirrors

50
Q

what do the lenses do in a refracting telescope

A

the objective lens captures and focuses the light to produce an image

the eyepiece lens magnifies this image

51
Q

what type of lense does a galilean telescope use?

A

a concave and a convex lens

52
Q

what are the advantages of a galilean telescope

A
  • the image is upright, not upside down
  • for the same length of telescope you can get better magnification
53
Q

what type of lenses does a keplerian telescope use?

A

two convex lenses

54
Q

what are advantage of a Keplerian telescope

A

larger field view (bigger image)

55
Q

what are the two types of reflecting telescope

A

newtonian and cassergrain

56
Q

which reflecting telescope is more complicated? and describe it

A

cassegrain is more complicated design.

shorter tube for same magnification

57
Q

list the advantages of reflecting telescopes(5)

A
  • it is much easier to make a large mirror than it is to make a large lens
  • a large mirror can have a large aperture
  • a large mirror can have a very large focal length
  • multiple mirrors can make this even larger
  • chromatic aberation is not a problem with mirrors
58
Q

explain chromatic aberration

A

different wavelengths of light may be refracted by different amounts. This causes a blurred image with coloured edges

59
Q

define magnification

A

how many times the image is bigger than the object

60
Q

how do you calculate magnification

A

m = focal length of objective/focal length of eyepiece

61
Q

define resolution

A

the ability of an optical instrument to distinguish between two points of light

62
Q

what are the two factors for resolution

A

1) the size of the aperture (the diameter of the objective lens)
larger aperture = better resolution

2) the wavelength that you are observing in
larger wavelength = poorer resolution

63
Q

what is light grasp proportional to

A

the amount of light entering telescope is proportional to the diameter of the aperture squared

64
Q

a telescope with double the diameter has…??

A

a telescope with double the diameter has four times the area, so four times the “light grasp”

65
Q

how many arcmins in 1 degree

A

1 degree = 60 arcmins

66
Q

define field of view

A

how much of the sky(the angle) that we can see through our telescope

67
Q

what did galileo discover with a telescope (4)

A
  • the moons surface had mountains and craters - the moon was not smooth
  • the phases of venus - sun is at centre of solar system
  • four moons around jupiter - not all bodies revolve around sun
  • the milky way contained stars - not just a band of cloud in space
68
Q

explain a fly by space probe

A

does not land on or orbit the target but just flies past taking measurements and images

69
Q

give an advantage of a fly by space probe

A

lots of measurements can be taken and transmitted back to earth, including images

70
Q

give a disadvantage of a fly by space probe

A

each body can only be flown by once, so not all parts of the bodies can be analysed

71
Q

give a real-life example of a fly by space probe

A

NEW HORIZONS

72
Q

explain an orbiter space probe

A

goes into orbit around the target body

73
Q

give an advantage of an orbiter space probe

A

entire body can be observed, more time to gather data

74
Q

give a disadvantage of an orbiter space probe

A

a lot of fuel is used to get a probe into orbit and data is limited to what can be obtained from space

75
Q

give a real-life example of an orbiter space probe

A

juno

76
Q

explain an impactor space probe

A

collides with the surface of the body. It can take measurements as it approaches the body and measurements can be made of the plume of debris by telescopes

77
Q

give an advantage of an impactor space probe

A

passes through body’s atmosphere and can dislodge material on the surface of the body to investigate compositions

78
Q

give a disadvantage of an impactor space probe

A

the impact probe has to send data back to earth via relay probe which also has to be sent to space and has to be at right place and right time → difficult as impacts can be unpredictable

79
Q

give a real life example of an impactor space probe

A

deep impact

80
Q

explain a lander space probe

A

lands on body

81
Q

give an advantage of a lander space probe

A

more detailed observations can be made of the immediate area around probe + experiments can be performed on the surface of a body

82
Q

give a disadvantage of a lander space probe

A

high faliure rate, probe can only examine the area close to where it landed

83
Q

give a real life example of a lander space probe

A

philae

84
Q

give some advantages of manned missions(4)

A
  • humans can cope with situations that robots can’t
  • humans are much more versatile than robots
  • humans are adaptable
  • manned missions are stepping stones towards human colonisation
85
Q

give some disadvantages of manned missions (6)

A
  • we need to keep the astronouts alive
    • manned missions are much more expensive
  • being in space for a long time isn’t good for your health (low gravity and radiation)
  • we have to worry about bringing them back
  • human lives at risk
  • training astronauts is expensive and takes a long time
86
Q

explain escape velocity

A

in order to escape earth, a spacecraft must reach escape velocity - decreases with altitude

gcse astronomy (3 decks)

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