The document discusses astronomy and the scientific study of celestial objects. It provides information on stars, galaxies, and the formation and components of the solar system. Specifically, it notes that astronomy is the study of matter in outer space, including the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies. It also summarizes that the universe started as a single point which exploded outward in the big bang and has been expanding ever since.

1. Astronomy

2. Astronomy
 The scientific study of matter in
outer space, especially the positions,
dimensions, distribution, motion,
composition, energy, and evolution of
celestial bodies and phenomena.

5. Forget the big bang, tune in to the big hum
THE big bang sounded more like a deep hum than a bang, according to an analysis of the radiation left over
from the cataclysm. Physicist John Cramer of the University of Washington in Seattle has created audio
files of the event which can be played on a PC. "The sound is rather like a large jet plane flying 100 feet
above your house in the middle of the night," he says. Giant sound waves propagated through the blazing hot
matter that filled the universe shortly after the big bang.
These squeezed and stretched matter, heating the compressed regions and cooling the rarefied ones. Even
though the universe has been expanding and cooling ever since, the sound waves have left their imprint as
temperature variations on the afterglow of the big bang fireball, the so-called cosmic microwave
background. Cramer was prompted to recreate the din- last heard13.7 billion years ago- by an11-year-old
boy who wanted to know what the big bang sounded like for a school project.
To produce the sound, Cramer took data from NASA's Wilkinson Microwave Anisotropy Probe. Launched in
2001, the probe has been measuring tiny differences in the temperature between different parts of the
sky. From these variations, he could calculate the frequencies of the sound waves propagating through the
universe during its first 760,000 years, when it was just 18 million light years across. At that time the
sound waves were too low in frequency to be audible. To hear them, Cramer had to scale the frequencies
100,000 billion billion times.
Nevertheless, the loudness and pitch of the sound waves reflect what happened in the early universe.
During the 100-second recording (http://www.npl.washington.edu/AV/BigBangSound_2.wav), the
frequencies fall because the sound waves get stretched as the universe expands. "It becomes more of a
bass instrument," says Cramer.
###
Author: Marcus Chown

6. The universe started as a single point.
That point was extremely dense.
It became unstable and exploded outward.
Today the universe continues to expand.

7. The Universe
 A massive explosion
occurred, between 12
–15 billion years ago,
and the universe has
been expanding ever
since

12. Evidence for Expansion
 The Doppler Effect is used as
evidence that galaxies are moving
away from us.
 When light moves away, it’s
wavelength is expanded (gets longer),
meaning it becomes redder.
 This is called the redshift.

13. Doppler Effect
 All galaxies show redshift in their spectra,
meaning they are moving away from us.

16. Measuring Distance
 Distances between celestial objects are extremely
large.
 Rather than miles, astronomers refer to a light-
year as a standard unit of distance.
 One light-year is the distance light travels in one
year.
 The speed of light is 186,000 mps (300,000 kps).
 Thus, one light-year is about 6 trillion miles.
 The nearest star to us (Proxima Centauri) is 4.2
light-years away.

17. Astronomical unit
 Another unit of distance is the
Astronomical Unit (AU).
 One AU is the distance from the
Earth to the Sun (93 million miles)
 Distances to other objects are given
in multiples of AU.

18. 1. 384,000 km
2. 1 AU
3. 100 AU
4. 1 light year
5. 75,000 light years
What is (approximately) the
size of the solar system?
Remember:
1 AU = distance Sun – Earth = 150 million km

19. Galaxies

20. Galaxies
 A galaxy is a collection of millions or
billions of stars.
 Galaxies can be spiral, elliptical,
spherical or irregular in shape.
 The Sun is part of the Milky Way
galaxy, which is a spiral galaxy.
 The Sun is located on one of the
spiral arms, far from the galactic
center.

21. Put these in order of size:
galaxy solar system universe
universe galaxy solar system

22. Regents Question
Which sequence correctly lists the relative
sizes from smallest to largest?
(1)our solar system, universe, Milky Way
Galaxy
(2)our solar system, Milky Way Galaxy,
universe
(3)Milky Way Galaxy, our solar system,
universe
(4)Milky Way Galaxy, universe, our solar
system

23. Regents Answer
(2)our solar system, Milky Way Galaxy,
universe

25.  A star is a huge, shining ball in space that produces a large
amount of light and energy.
 Stars come in many sizes.
 About 75% are apart of groups that orbit each other.
 They are grouped in large structures called galaxies. (Milky
Way).
 Stars have life-cycles like humans.
 A stars color depends on surface temperature.

26. Stars
 Stars are burning masses of gas.
 Their energy is the result of nuclear
fusion, in which Hydrogen atoms
combine to form Helium atoms,
releasing energy.
 Electromagnetic energy is radiated by
stars.

27. Star Characteristics
 Stars vary in their size, mass,
density, temperature and composition.
 Luminosity – the actual brightness of
a star
 Luminosity depends only a star’s size
and temperature

28. Composition
 Stars are primarily made of Hydrogen
and Helium
 Many other elements are present in
stars in small amounts
 A star’s composition can be
determined by spectral analysis.

30. Spectral Analysis
 Spectral analysis is the study of the
electromagnetic spectrum emitted by
a star, using a spectroscope.
 Each element emits radiation is a
specific set of wavelengths

31. Electromagnetic Spectrum

32. Color and Temperature

33. ESRTs p15

35. ESRTs p15

36. What type of star is our
Sun classified as?ESRT p15
Circle where it is on the chart

37. The H-R Diagram
 The Hertzsprung-Russell (H-R)
Diagram is a graph of stars,
comparing luminosity and
temperature.
 Stars are categorized according to
these two properties

38. The H-R Diagram
 Main Sequence – band into which most
stars fall
– High temperature, high luminosity
– Low temperature, low luminosity
 Red Giants and Supergiants – cooler,
very luminous stars that are very
large
 White Dwarfs – hotter, low luminosity
stars that are small

40. Shade the chart where all of the
stars are hotter than our sun.
Draw a line on the chart which
separates those stars brighter
than our sun and those less bright.
ESRTs p15

41. The H-R Diagram

42. Regents Question
Which statement describes the general
relationship between the temperature
and the luminosity of main sequence
stars?
(1) As temperature decreases, luminosity
increases.
(2) As temperature decreases, luminosity
remains the same.
(3) As temperature increases, luminosity
increases.
(4) As temperature increases, luminosity
remains the same.

43. Regents Answer
(2) As temperature increases,
luminosity increases.

44. Regents Question
Compared to other groups of stars,
the group that has relatively low
luminosities and relatively low
temperatures is the
(1)Red Dwarfs (3)Red Giants
(2)White Dwarfs (4)Blue Supergiants

45. Regents Answer
(1)Red Dwarfs

46. Regents Question
Which list shows stars in order of
increasing temperature?
(1)Barnard’s Star, Polaris, Sirius, Rigel.
(2)Aldebaran, the Sun, Rigel, Procyon
B.
(3)Rigel, Polaris, Aldebaran, Barnard’s
Star.
(4)Procyon B, Alpha Centauri, Polaris,
Betelgeuse.

47. Regents Answer
(1)Barnard’s Star, Polaris,
Sirius, Rigel.

48. Star Life Cycles
 Stars are born in a cloud of gas and dust,
called a nebula.
 Most stars remain as main sequence stars,
until their hydrogen fuel is depleted
 An average star, like the sun, would go
through the Red Giant phase, eventually
becoming a White Dwarf.
 A large star would become a Supergiant,
then explode as a supernova. The result
may be a neutron star, pulsar or black hole.

51. Sun
http://en.wikipedia.org/wiki/Image:Sun920607.jpg
Mythology
The Sun God. Greeks Called it Hellos
Mass
333 400 times the mass of the Earth
Diameter
1 392 000 km (109 x Earth’s
diameter)
Gravity
28 times that on Earth
Surface Temperature
6000°C (average). From 4500 to
2000000°C up to 15000000°C in the
core.
Period of rotation
(day)
Equator 26 Earth days, poles 37 Earth
days
Tilt of axis
122°

54. Solar System Components
 The Solar System includes:
• The Sun, a medium size, middle-aged
star
• The eight planets and associated moons
• Asteroids – chunks of rock found mostly
in a belt between Mars and Jupiter
• Comets – mass of frozen gas and rock
• These are considered celestial objects
which appear in the sky during day and
night.

55. Formation of the Solar System
 4.6 Billion years ago a large cloud of gas, ice & dust
existed
 Began to contract & slowly rotate
– Contraction increased density & rotation
– Gravity began to pull material toward the center
– Density increases = increased rotation & gravity
– Begins to form disk with large center
– Central mass begins to heat up due to contraction
• Temperatures reach 10 million 0K
• Hydrogen atoms begin to fuse together forming
Helium
• Fusion occurs, driving the formation of our Sun
– The material outside the central mass forms planets

57. The Parts of Our Solar System
 The sun is the center of the Solar System
– Inner Planets: Also called Terrestrial planets: first
four planets. They are solid, rock like structures
– Asteroid belt: band of rocks orbiting the sun
– Outer Planets: Also called Jovian planets: The 4
planets farthest from the sun
• 4 are made up of mainly lighter element gases
• Last two are frozen materials

58. Two Kinds of Planets
Planets of our solar system can be divided into
two very different kinds:
Terrestrial (earthlike) planets:
Mercury, Venus, Earth, Mars
Jovian (Jupiter-like) planets: Jupiter,
Saturn, Uranus, Neptune

59. Size of Terrestrial Planets
Compared to Jovian Planets

60. Terrestrial
Planets
Four inner
planets of the
solar system
Relatively small in
size and mass (Earth
is the largest and
most massive)
Rocky surface
Surface of Venus can not be seen
directly from Earth because of its
dense cloud cover.

61. The Jovian Planets
Much larger in mass
and size than terrestrial
planets
Much lower
average density
All have rings (not
only Saturn!)
Mostly gas; no
solid surface

62. Asteroids
The total mass of all the asteroids
is less than that of the Moon.
-rocky objects with round or
irregular shapes
lie in a belt between Mars and Jupiter

63. The Asteroid Belt
Pluto
(Distances and times reproduced to
scale)
Most asteroids
orbit the sun in a
wide zone between
the orbits of Mars
and Jupiter.

64. Asteroids
– Believed to be a planet that never formed
– Range in size from dust to almost Moon size
– Photographed by Galileo probe
• Some Named Asteroids:
– Ceres: 940 km (Largest known)
– Pallas: 523 km
– Vesta: 501 km
– Juno: 244 km
– Gaspra & Ida

67. only visible when
they are close to
the sun

68. Comets
Mostly objects in highly elliptical orbits,
occasionally coming close to the sun.
Icy nucleus, which evaporates
and gets blown into space by
solar wind pressure.

69. Comet Information:
 Comet Composition:
– Dust, rock, frozen methane, ammonia, and water
– Comets normally look like dirty snowballs
– When they get close to stars, they change
• They begin to vaporize & Glow
• Forms a coma (tail) from the nucleus (head)
– Coma: glowing trail of particles
– Always points away from the star
– Comets eventually break up into space debris
 Oort Cloud: large collection of comets beyond
Pluto

71. Meteoroids
Small (µm – mm sized)
dust grains throughout the
solar system
If they collide with Earth,
they evaporate in the
atmosphere.
Visible as streaks of light
(“shooting stars”):
meteors.

73. LARGEST METEORITE TO
HIT EARTH – Namibia, Africa

74. Meteoroids, Meteors, & Meteorites
 Meteoroids: chunks of rock
– Randomly moving through space
– Usually leftover comet or asteroid debris
 Meteor: Meteoroid that enters Earth’s atmosphere
– Heat up & begin to glow = shooting star
– Most burn up before reaching the surface
– Many meteors at one time = meteor shower
 Meteorite: Meteor that does not totally burn up, &
strikes the Earth’s surface
– Impact creates a crater

75. Cosmic Collision Video Clip

77. http://solarsystem.jpl.nasa.gov/multimedia/gallery/solarsys_scale.jpg(Distance between objects not to scale)

78. How small are we?
source: Celestia (application)(Distance between objects not to scale)
Earth

79. Earth
How small are we?
source: Celestia (application)(Distance between objects not to scale)

80. Relative distance of planets
 Sun = 1300mm
diameter (blown
up garbage bag)
 Mercury = 4.5mm
(coffee bean) 54m
from Sun
 Venus = 11.3mm
(small blueberry)
101m from Sun
 Earth = 11.9mm
(small blueberry)
139m from Sun
 Mars = 6mm (pea)
213m from Sun
image source: Google
Earth

81. Relative distance of planets
 Jupiter = 133.5mm
(large grapefruit)
727m from Sun
 Saturn = 112.5mm
(large orange)
1332m from Sun
 Uranus = 47.7mm
(Kiwi) 2681m from
the Sun
 Neptune = 46.2mm
(nectarine) 4200m
from the Sun
 Pluto = 2mm (grain
of rice) 5522m
from the Sun
image source: Google
Earth

82. Relative distance of planets
 Jupiter = 133.5mm
(large grapefruit)
727m from Sun
 Saturn = 112.5mm
(large orange)
1332m from Sun
 Uranus = 47.7mm
(Kiwi) 2681m from
the Sun
 Neptune = 46.2mm
(nectarine) 4200m
from the Sun
 Pluto = 2mm (grain
of rice) 5522m
from the Sun
image source: Google
Earth

83.  A planet is a body that is in orbit
around the Sun, has enough mass for
its self-gravity to overcome forces
(nearly round) shape, and clears the
neighborhood around its orbit.
Planet order (closest to the
sun to furthest):
 MERCURY
 VENUS
 EARTH
 MARS
 JUPITOR
 SATURN
 URANUS
 NEPTUNE

84.  Position: Closest planet to the Sun.
 Atmosphere: Like Earth’s moon, very little.
 Landscape: Many craters, a little ice. Cliffs
and valleys present.
 Temperatures: Super-heated by the sun in
the day. At night temperatures reach
hundreds of degrees below freezing. (Not as
warm as you would think).
 Year (Full rotation around the sun): 88 days.
 Moons: 0
 Rings: 0

85. Mercury
http://en.wikipedia.org/wiki/Image:Reprocessed_Mariner_10_image_of_Mercury.jpg
Mythology
God of travel, commerce and
thieves
Mass
0.056 times that of Earth
Moons
None
Diameter
4878 km ( = 0.38 x Earth’s
diameter)
Surface
Similar to Earth’s moon
Gravity
0.38 times that on Earth
Surface Temperature
–170°C to 430°C
Period of rotation (day)
59 Earth days
Tilt of axis
0°
Distance from Sun
0.39 AU (58 million kilometres)
Time to orbit Sun
(year)
88 Earth days

86.  Position: 2nd planet from the sun.
 Atmosphere: Thick enough to trap heat,
hurricane winds, lightning, and acid clouds.
 Landscape: Volcanoes and deformed mountains.
 Temperatures: Intense heat.
 Year (Full rotation around the sun): 225 Earth
days.
 Moons: 0
 Rings: 0
Venus

87. Venus
http://en.wikipedia.org/wiki/Image:Venus-real.jpg
Mythology
Goddess of love and beauty
Mass
0.815 times that of Earth
Moons
None
Diameter
12 103 km ( = 0.95 x Earth’s
diameter)
Surface
Extensive cratering, volcanic
activity.
Gravity
0.9 times that on Earth
Surface Temperature
460°C
Period of rotation (day)
243 Earth days
Tilt of axis
30°
Distance from Sun
0.72 AU (108 million kilometres)
Time to orbit Sun
(year)
225 Earth days

88.  Position: 3rd planet from the sun.
 Atmosphere: Suitable air pressure to
have life. Air is made of oxygen.
 Landscape: The only planet that has
liquid on the surface, rocky, land
formations.
 Temperatures: Suitable for life. Ranges
from locations on Earth.
 Year (Full rotation around the sun): 365
Earth days.
 Moons: 1
 Rings: 0

89. Earth
http://en.wikipedia.org/wiki/Image:The_Earth_seen_from_Apollo_17.jpg
Mythology
Gaia—mother Earth
Mass
1.0 times that of Earth (5 980 000
000 000 000 000 000 000 kg)
Moons
One (‘the Moon’)
Diameter
12 756 km
Surface
Two-thirds water, one-third land
Gravity
1.0 times that on Earth
Surface Temperature
average 22°C
Period of rotation (day)
1 Earth day
Tilt of axis
23.5°
Distance from Sun
1 AU (150 million kilometres)
Time for light to reach
Earth
8 minutes
Time to orbit Sun
(year)
365.25 Earth days

90.  Position: 4th planet from the
sun.
 Atmosphere: Thinner air than
Earth.
 Landscape: Frozen water below
the surface, rocky, dusty, and
has craters.
 Temperatures: Like Earth, but
drier and colder
 Year (Full rotation around the
sun): 687 Earth days.
 Moons: 2
 Rings: 0

91. Mars
http://en.wikipedia.org/wiki/Image:2005-1103mars-full.jpg
Mythology
God of war
Mass
0.107 times that of Earth
Moons
2 (Phobos—diameter 23 km,
Deimos—diameter 10 km)
Diameter
6794 km ( = 0.53 xEarth’s
diameter)
Surface
Soft red soil containing iron oxide
(rust). Cratered regions, large
volcanoes, a large canyon and
possible dried-up water channels.
Gravity
0.376 times that on Earth
Surface Temperature
–120°C to 25°C
Period of rotation (day)
1.03 Earth days
Tilt of axis
25.2°
Distance from Sun
1.52 AU (228 million kilometres)
Time to orbit Sun
(year)
687 Earth days
Time to reach Mars
9 months

92.  Position: 5th
planet from the
sun.
 Atmosphere:
Colorful clouds,
until it is squished
unto liquid. Cold
and windy, giant
storms.
 Landscape: Thick
super hot soup.
 Temperatures:
Extremely cold at
clouds. Extremely
hot and cold
radiation.

93. Jupiter
http://en.wikipedia.org/wiki/Image:Jupiter.jpg
Mythology
Ruler of the Gods
Mass
318 times that of Earth
Moons
At least 28 moons and four rings,
including the four largest moons:
Io, Ganymede, Europa and Callisto.
These are known as the ‘Galilean’
moons.
Diameter
142 984 km ( = 11.21 x Earth’s
diameter)
Surface
Liquid hydrogen
Gravity
2.525 times that on Earth
Surface Temperature
Cloud top –150°C
Period of rotation (day)
9 hours 55 minutes
Tilt of axis
3.1°
Distance from Sun
5.2 AU (778 million kilometres)
Time to orbit Sun
(year)
11.8 Earth years

94.  Position: 6th planet from the sun.
 Atmosphere: Composed mostly of gas
with no solid surface. Cloud strips.
 Landscape: No solid surfaces, high
pressures turn gas into liquids.
 Temperatures: Rings made out of water
ice, really cold.

95. Saturn
http://en.wikipedia.org/wiki/Image:Saturn_from_Cassini_Orbiter_
%282007-01-19%29.jpg
Mythology
God of agriculture
Mass
95.184 times that of Earth
Moons
At least 30 moons and rings in
seven bands
Diameter
120 536 km (= 9.45 x Earth’s
diameter)
Surface
Liquid hydrogen
Gravity
1.064 times that on Earth
Surface Temperature
–180°C
Period of rotation (day)
10 hours 39 minutes
Tilt of axis
26.7°
Distance from Sun
9.6 AU (1400 million kilometres)
Time to orbit Sun
(year)
29.5 Earth years

96.  Position: 7th planet from the sun.
 Atmosphere: Gets thicker and
thicker, until it is squished unto
liquid. Cold and windy.
 Landscape: Layer of superheated
water and gases that form bright
clouds.
 Temperatures: Extremely cold at
cloud tops and superheated towards
the center.

97. Uranus
http://en.wikipedia.org/wiki/Image:Uranusandrings.jpg
Mythology
Father of Saturn
Mass
14.54 times that of Earth
Moons
At least 21 moons and 11 rings
Diameter
51 200 km (= 4.01 x Earth’s
diameter)
Surface
Likely to be frozen hydrogen and
helium
Gravity
0.903 times that on Earth
Surface Temperature
–220°C
Period of rotation (day)
17 hours 14 minutes
Tilt of axis
98°
Distance from Sun
19.2 AU (2875 million kilometres)
Time to orbit Sun
(year)
84 Earth years

98.  Position: Furthest from the sun (Cannot see
without a Telescope). 8th planet.
 Atmosphere: Very Windy, cold clouds, a layer of
methane gas (giving it a blue color), storms as
large Earth.
 Landscape: Scientist think it may have an ocean
of super hot lava.
 Temperatures: Cold

99. Neptune
http://en.wikipedia.org/wiki/Image:Neptune.jpg
Mythology
God of the sea
Mass
17.15 times that of Earth
Moons
8 moons and 5 rings
Diameter
49 528 km ( = 3.88 x Earth’s
diameter)
Surface
Frozen hydrogen and helium
Gravity
1.135 times that on Earth
Surface Temperature
–220°C
Period of rotation (day)
16 hours 7 minutes
Tilt of axis
29.3°
Distance from Sun
30.1 AU (4500 million kilometres)
Time to orbit Sun
(year)
165 Earth years

100.  Pluto is NOT
considered a planet
anymore!
 It is classified as a dwarf
planet.
 Temperatures: Extremely
cold, covered with frost.
 Year (Full rotation around
the sun): 248 Earth years.
 Moons: 3
 Pluto is very hard to
see, if with a really
powerful teloscope.

101. The planets to scale. The rings of the gas giants are not shown.

102. http://www.solarviews.com/cap/misc/obliquity.htm
Comparing tilt of axis

103. Draw a line across the table between
the terrestrial and jovian planets and label.

104. Which are more dense?
Jovian or terrestrial

105. Which have more moons ?
Jovian or terrestrial

106. Which have longer periods of revolution?
Jovian or terrestrial

107. Which are larger in size on average ?
Jovian or terrestrial

108. Which planet has the longest day?

109. Which planet has the longest year?

110. Regents Question
Which object in our solar
system has the greatest
density?
(1) Jupiter (3) the Moon
(2) Earth (4) the Sun

111. Regents Answer
(2) the Earth

112. 1. What is the solar system (what objects make up
the Solar System?
2. Draw a diagram of planet placement and list the
planets in order from the closest to the furthest
from the sun.
3. When did the solar system form?
4. When did the universe form?
5. What is the difference between the Jovian and
Terrestrial planets?
6. What is the difference between a meteor,
meteoroid, and meteorite?
7. What is your favorite planet and why?

113. Planetary Orbits
Pluto
Earth
Venus
Mercury
Do Now:
Make 3 observations
about this animation
(Distances and times reproduced to
scale)

114. http://solarsystem.jpl.nasa.gov/multimedia/gallery/vis_orb.jpg

115. http://solarsystem.jpl.nasa.gov/multimedia/gallery/outer_orb.jpg

116. How the planets move
 All planets move in the same
plane (a large imaginary flat
surface)

117. Tipped over by
more than 900
Mercury and Pluto: Unusually highly inclined orbits
Planetary Orbits

118. Planetary Orbits
Pluto
Earth
Venus
Mercury
All planets in almost
circular (elliptical)
orbits around the sun,
in approx. the same
plane (ecliptic).
Sense of revolution:
counter-clockwise
Sense of rotation:
counter-clockwise
(with exception of
Venus, Uranus, and
Pluto)
Orbits generally
inclined by no
more than 3.4o
Exceptions:
Mercury (7o)
Pluto (17.2o)
(Distances and times reproduced to
scale)

120. Orbits
 Revolution – the movement of an
object around another object
 Orbit – the path taken by a revolving
object
 Celestial objects have elliptical orbits

121. Elliptical Orbit
 A circle has one central point, called a
focus.
 Ellipses have two points, called foci.

122. Eccentricity

123. Calculate the eccentricity
of the ellipse below:
Formula: eccentricity = distance between foci
length of major axis
length of major axis

124. Regents Question
Which object is located at one
foci of the elliptical orbit of
Mars?
(1)the Sun (3)Earth
(2)Betelgeuse (4)Jupiter

125. Regents Answer
(1)the Sun

126. Regents Question
The bar graph below shows one planetary characteristic,
identified as X, plotted for the planets of our solar
system.
Which characteristic of the planets in our solar system is
represented by X?
(1)mass (3)eccentricity of orbit
(2)density (4)period of rotation

127. Regents Answer
(3)eccentricity of orbit

128. Regents Question
Which planet has the least
distance between the two
foci of its elliptical orbit?
(1)Venus (3)Mars
(2)Earth (4)Jupiter

129. Regents Answer
(1)Venus

130. Laws of Planetary Motion
 Devised by German
astronomerJohannes Kepler:
1. The planets move in elliptical orbits,
with the Sun at one focus
2. The line joining the Sun and a planet
sweeps equal areas in equal intervals of
time
3. The square of the time of revolution
(T²) is proportional to the planet’s
mean distance from the Sun (R³)

131. Kepler’s First Law
• Planets move
around sun in
elliptical orbits.
• Sun is at one
focus point.
• Flatness called
eccentricity
• Formula in ESRT.
Focus
points
Major
axis
Eccentricit
y =
Distance between
fociLength of major axis

132. Kepler’s Second Law
Area of orange section is equal.
Distance along orbit is not the same. But the
time covered is equal. eccentricity website

133. Kepler's Third Law
Not drawn to
scale.
Earth – 150 mill.
Km, 365 days

134. Orbital Energy
 Gravitation – the force of attraction
between 2 objects
 Inertia – the tendency of an object in
motion to continue in motion along a
straight path
 The interaction of gravity and inertia
keep planets in orbit

135. Energy Transfer
 Energy is transferred between
potential and kinetic as a planet
orbits the Sun.

136. Orbital Velocity
 The Earth’s orbital velocity is highest
when kinetic energy is the highest.
 This occurs when the Earth is nearest
to the Sun in its orbit.

137. When
furthest
from Sun
When closest
to Sun

138. eccentricity website

139. Which planet has the least
perfectly circular orbit?

140. Which planet has the most
perfectly circular orbit?