igcse edexcel atomic physics

1. Astrophysics
天体物理学

2. Outline
• Motion in the universe
• Stellar Evolution 恒星演化
• Cosmology 宇宙论

4. The Milky Way 银河系
The Milky Way is the name of
our galaxy

5. Galaxies 星系
Galaxies consist of billions of
stars bound together by the
force of gravity.
There are at least 200 billion
galaxies in our universe and
each containing on average 2
billion stars.
is the nearest
sprial galaxy to
the Milky Way

6. 螺旋形
棒旋星云

9. The solar system
The solar system consists of the sun orbited by eight planets and their
moons, some dwarf planets along with many asteriods and comets.

10. The solar System
• Mercury 水星
• Venus金星
• Earth地球
• Mars火星
• Jupiter木星
• Saturn土星
• Uranus天王星
• Neptune海王星

11. Planet
A planet is a body that orbits the
sun, is massive enough for its own
gravity to make it round.
And has cleared its neighbourhood
of smaller objects around its orbit

12. Dwarf Planet 矮行星
A dwarf planet is a celestial body
orbiting the sun that is massive
enough to be spherical as a result
of its own gravity.
But has not cleared its
neighbouring region of other
similar bodies.

13. Planets vs. Dwarf Planets
Difference:
The only difference between a planet and a dwarf planet is the
area surrounding each celestial body.
A dwarf planet has not cleared the area around its orbit, while a
planet has.

14. Asteriods小行星
An asteriod is a celestial body
orbiting the sun that is not massive
enough to be spherical as a result
of its own gravity.
An asteriod is made of metals and
rocky materials.
Most asteriods are found between
the orbits of mars and jupiter-a
region called 'the Asteriods Belt'.

15. Dwarf Planet vs. Asteriods
The difference between dwarf planets
and asteroids is the relationship between
large and small, spherical or not.
Dwarf planets are definitely bigger than
asteroids, mostly by mass.
For dwarf planets to be spherical or
roughly spherical, asteroids are messy.

16. Moons卫星
A moon orbits a planet
Note: A number of dwarf planets and asteriods also have moons, for example
Pluto has theree moons

17. Comets 彗星
A comet is a body made of dust,
ice and rocky materials that
occupies a highly elongated orbit.
When the comet passes close to
the sun. some of the comet's frozen
gases evaporate. These form a long
tail that shines in the sunlight

18. Asteriods vs. Comets
The asteriods are made up of metals and rocky materials,
while the comets are made up of ice, dust and rocky
materials.

19. Meteor 流星 vs. Meteorites 陨石
Earth often encounters small alien object. These
small objects would collide violently with the
Earth's atmosphere and burn up. This is a
meteor.
Most meteors originate from small amounts of
material left behind in the wake of comets.
If a meteor falls to the ground before it burns up,
it's a meteorite.

20. Period T 周期
This is the time taken for a
planet to complete one orbit
around the sun
It increases with a planets
distance from the sun

21. Planetary orbits 行星轨道
The orbits of the planets are
slightly squashed circuler (ellipses
椭圆形) with the sun quite close
to the center

23. WHY?

33. Orbital Speed

35. Question 1
Calculate the orbital speed of the Earth around the Sun.
(Earth orbital radius = 150 million km)

36. Question 2
Calculate the orbital speed of the Moon around the Earth.
(Moon orbital radius = 380,000 km; orbit time = 27.3 days)

37. Question 3
Calculate the orbital speed of the ISS(International space station) around the
Earth.
(ISS orbital height = 355km; orbit time = 91 minutes; Earth radius = 6378 km)

38. Question 4
Calculate the orbital time of the a satellite that has a speed of 3075km/s
and height above the earth of 35906km.
(Moon orbital radius = 380,000 km; orbit time = 27.3 days)

39. Satallites
Earth observation
and monitoring
satellites
Communication
Statellites

40. Communication Satallites

41. Communication Satallites

42. Communication Satallites

44. Orbit Motion

47. PASTPAPER1

48. PASTPAPER2

49. PASTPAPER3

52. Beginning
Cloud of dust and gas
Nebula 星云

53. Gravity pulls dust and gas together to form protostar.
原恒星

54. More and more particle collide and join the protostar
---->get bigger
---->attract more dust and gas
Gravity also squeezes the protostar
---->more dense
---->particles collide more often

55. Nulcear Fussion
--gives out energy
Pin = Pout, stable
SUN
主序星

57. Pin>Pout, then squeeze the main sequence star

58. Until the star is small and hot, the nuclear fusion can start again and expand the size.

61. Red Giant 红巨星

62. Red Giant 红巨星

63. Red Giant 红巨星
白矮星
黑矮星

64. Red Super Giant 红超巨星

65. Red Super Giant 红超巨星
超星星

66. Red Super Giant 红超巨星
Once the fusion reactions inside the
red supergiant finally finish, the core of
the star will collapse suddenly causing
a gigantic explosion

67. Recall

69. Classification of Star
Stars come in a wide range of sizes
and colours, from yellow stars to
red dwarfs, from blue giants to red
supergiants
These can be
classified according to
their colour

70. HR Diagram

71. Absolute Magnitude
Astronomers measure the
brightness of stars at a
standard distance using the
absolute magnitude scale
The brighter the star, the smaller the magnitude
The dimmer the star, the larger the magnitude
The absolute magnitude of stars is a measure of how bright they would be
if they were all the same distance away from Earth

72. Absolute Magnitude
A girl sees two stars in space and A
appears brighter than B because A is
closer.
However, B is actually brighter. So the
absolute magnitude system is based on
bringing both stars to the same
distance (10 parsecs) away and
comparing. In which case now B is
actually brighter.

73. Apparent Magnitude
Apparent magnitude is is the
brightness measured by an
observer from the object.
The smaller the distance
between the observer and
object, the greater the
apparent brightness.
Bright and far away
Dim and close

74. Apparent Magnitude
Two objects that have the same apparent magnitude, as seen from
the Earth, may either be:
• At the same distance from the Earth, with the same luminosity.
• At different distances from the Earth, with different values of
luminosity.
Look the same!

75. Absolute Magnitude vs. Apparent Magnitude
Absolute Magnitude is depends only on the luminosity itself, because
they will be compared in same distance.
Apparent Magnitude is depends on both luminosity and distance.

77. The Big Bang Theory
• Around 14 billion years ago, the
Universe began from a very small
region that was extremely hot and
dense
• Then there was a giant explosion,
which is known as the Big Bang

78. The Big Bang Theory
• This caused the universe to
expand from a single point,
cooling as it does so, to form
the universe today
• Each point expands away
from the others
• This is seen from galaxies
moving away from each other,
and the further away they
are the faster they move

79. Evidence
• Red Shift---first evidence
• CMBR = cosmic microwave background radiation

80. Red Shift
Red shift: they are moving
away from each other
Blue shift: they are
moving towards to each
other

81. Red Shift
University is constant size and
always fixed.

82. Red Shift

83. Red Shift
1. Spaces and galaxies are moving away from each other
2. The further the distance, the faster the speed.

84. Red Shift
Doppler's effect: The change in distance between the
wave source and observer is causing the red shift. So
the red shift is also explained as doppler's effect

85. Doppler Effect

86. Doppler Effect

87. Example

88. CMBR

89. CMBR
In 1980:
A cell phone encodes the
sounds of the caller's voice in
microwaves by changing the
frequency of the waves.
Now:
Filter!

90. CMBR
Red Shift as well!!!!

91. CMBR

92. CMBR
1. CMBR comes from all direction
2. CMBR began as gamma radiation and then wavelength increased.