unit8astronomy09-10-101024160150-phpapp02 (1).pdf

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

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

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

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

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.

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

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.

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.

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

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.

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

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

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

 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.

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.

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

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.

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

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

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

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

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

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.

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

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

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.

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

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.

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°

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.

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

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

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

Size of Terrestrial Planets
Compared to Jovian Planets

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.

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

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

The Asteroid Belt
P
l
u
t
o
(Distances and times reproduced to
scale)
Most asteroids
orbit the sun in a
wide zone between
the orbits of Mars
and Jupiter.

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

only visible when
they are close to
the sun

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.

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

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.

LARGEST METEORITE TO
HIT EARTH – Namibia, Africa

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

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

How small are we?
source: Celestia (application)
Earth

Earth
How small are we?
source: Celestia (application)

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

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

 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

 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

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

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

Venus
http://en.wikipedia.org/wiki/Image:Venus-real.jpg
Mythology Goddess of love and beauty
Moons None
Diameter
12 103 km ( = 0.95 x Earth’s
diameter)
Surface
Extensive cratering, volcanic
activity.
Surface Temperature 460°C
Period of rotation (day) 243 Earth days
Tilt of axis 30°
Time to orbit Sun
(year)
225 Earth days

 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

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
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

 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

Mars
http://en.wikipedia.org/wiki/Image:2005-1103mars-full.jpg
Mythology God of war
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.
Surface Temperature –120°C to 25°C
Period of rotation (day) 1.03 Earth days
Tilt of axis 25.2°
Time to orbit Sun
(year)
687 Earth days
Time to reach Mars 9 months

 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.

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
Surface Temperature Cloud top –150°C
Period of rotation (day) 9 hours 55 minutes
Tilt of axis 3.1°
Time to orbit Sun
(year)
11.8 Earth years

 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.

Saturn
http://en.wikipedia.org/wiki/Image:Saturn_from_Cassini_Orbiter_
%282007-01-19%29.jpg
Mythology God of agriculture
Moons
At least 30 moons and rings in
seven bands
Diameter
120 536 km (= 9.45 x Earth’s
diameter)
Surface Liquid hydrogen
Surface Temperature –180°C
Tilt of axis 26.7°
Time to orbit Sun
(year)
29.5 Earth years

 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.

Uranus
http://en.wikipedia.org/wiki/Image:Uranusandrings.jpg
Mythology Father of Saturn
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
Tilt of axis 98°
Time to orbit Sun
(year)
84 Earth years

 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

Neptune
http://en.wikipedia.org/wiki/Image:Neptune.jpg
Mythology God of the sea
Moons 8 moons and 5 rings
Diameter
49 528 km ( = 3.88 x Earth’s
diameter)
Surface Frozen hydrogen and helium
Tilt of axis 29.3°
Time to orbit Sun
(year)
165 Earth years

 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.

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

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

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

Which are more dense?
Jovian or terrestrial

Which have more moons ?

Which have longer periods of revolution?

Which are larger in size on average ?

Which planet has the longest day?

Which planet has the longest year?

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

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?

Planetary Orbits
P
l
u
t
o
Earth
Venus
Mercury
Do Now:
Make 3 observations
about this animation
scale)

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

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

How the planets move
The four innermost planets
orbit the Sun in almost circular
orbits
The larger outer planets move
in more elliptical or oval orbits
All planets move in the same
plane (a large imaginary flat
surface)

Planetary Orbits
P
l
u
t
o
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)
scale)

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

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

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

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

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

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

Regents Answer
(3)eccentricity of orbit

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

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)

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
foci
Length of major axis

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

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

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

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

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.

When
furthest
from Sun
When closest
to Sun

Which planet has the least
perfectly circular orbit?

Which planet has the most
perfectly circular orbit?

Models of the Solar System
 Based upon observations of the
apparent motion of celestial objects.
 Geocentric Model – Earth is the
center of the solar system, and all
objects revolve around it.
 Used epicycles (small sub-orbits) to
explain retrograde (backward) motion
of planets

Explain the difference
between
the geo- and helio-centric
models of the solar system.
Earth-
centered
Sun-
centered

Models of the Solar System
 Heliocentric Model – The Sun is at
the center, and the planets revolve
around it
 The planets’ orbits are governed by
Kepler’s Laws:
• Elliptical orbits
• Velocity changes during revolution
• Planets further from Sun revolve slower

Shape of the Sky
•Dome shaped
•Latitude =
Altitude of
Polaris (N.
star)
•You at
intersection
of N-S, E-W
line
•Zenith- directly above
90°

Apparent Daily Motion
 Celestial objects appear to move in
the sky
 This is due to the Earth’s rotation
 Objects appear to move 15° per hour,
because Earth rotates 360° in 24
hours. 360/24 = 15

How long is one rotation of
Earth?
How long is one revolution of Earth?

Rising and Setting
of the Sun
Rising and Setting
of the Moon
The Seasons
Changing
Constellations
Movement of Stars
through the sky

Regents Question
Which observation provides the best
evidence that Earth revolves around the
Sun?
(1)The constellation Orion is only visible in
the night sky for part of the year.
(2)The North Star, Polaris, is located above
the North Pole for the entire year.
(3)The sun appears to move across Earth’s
sky at a rate of 15○
/hr.
(4)The Coriolis effect causes Northern
Hemisphere winds to curve to the right.

Regents Answer
(1)The constellation Orion is
only visible in the night sky
for part of the year.

One rotation = 360°
Time for one rotation = 24 hours
360° ÷ 24 = 15°/hr

Regents Question
Earth’s rate of rotation is
approximately
(1)1○
per day (3) 180○
per
day
(2)15○
per day (4) 360○
per day

Regents Answer
(1)15○
per day

Star trails looking North
Polaris
Stars are so far
away the appear
stationary (not
moving).
Why do they
have this
pattern?

Constellations are groupings of stars that make an
imaginary image in the night sky. They have been
named after mythological characters, people,
animals and objects. In different parts of the world,
people have made up different shapes out of the
same groups of bright stars. It is like a game of
connecting the dots. In the past constellations have
became useful for navigating at night and for
keeping track of the seasons.

Regents Question
Which object is closest to Earth?
(1)The Sun (3)the moon
(2)Venus (4)Mars

Apparent Solar Motion
 The sun appears to move across the sky,
like all celestial objects.
 The sun’s apparent path in the sky
varies by latitude and season.

Regents Question
If Earth’s axis were tilted less
than 23.5
○
, which seasonal
average temperature change
would occur in New York State?
(1)Spring and fall would be cooler.
(2)Spring and fall would be warmer.
(3)Winter would be cooler.
(4)Summer would be cooler.

Regents Answer
(4)Summer would be cooler.

How many degrees
did the stars move
from diagram 1 to
diagram 2?
30° (2 hours x 15°)

How can you find
Polaris?
It’s the only one that
didn’t move

What hemisphere
must you be in?
Why?
Northern
Because Polaris can
only been seen in the
North

What direction must
you be looking?
North

What direction do
the stars appear to
move?

What causes the
stars appear to move?

Regents Question
In the Northern Hemisphere, planetary
winds blowing from north to south are
deflected, or curved, toward the west.
This deflection is caused by the
(1)unequal heating of land and water
surfaces.
(2)movement of low-pressure weather
systems.
(3)orbiting of Earth around the Sun.
(4)spinning of Earth on its axis.

Regents Answer
(4) spinning of Earth on its axis.

Regents Question
The diagram below shows how Earth is
illuminated [lighted] by the Sun as viewed
from above the North Pole.
In which orbital position would Earth be
illuminated as shown?
(1)A (3) C
(2)B (4) D

Four Seasons
Name the four seasons and
their starting date.
•Summer Solstice– June 21
•Autumn Equinox– September
21
•Winter Solstice– December
21
•Spring Equinox – March 21

What changes do we observe
during seasons?
Sun’s
altitude
changes
with the
season.
Highest – June 21, Lowest – Dec.
21, But NEVER overhead at our
latitude.

during seasons?
Sun rise and
Sun set
positions
change with
the seasons.
South of E/W
in fall and
winter. North of E/W in
spring and
summer.
Sun rise in DC

during seasons?
Day length –
Duration of
Insolation
Longest on Summer Solstice, June
21.
Shortest on
Winter Solstice,
Dec. 21
12 hours on
Equinox for all.

during seasons?
What to know about the Summer Solstic
1. June 21, longest day of the year.
2.Sun at highest altitude at noon.
3.24 hrs of daylight at North Pole.
4.Direct sun ray at 23.5° north
latitude.
5.Sun rise – NE, Sun set - NW

during seasons?
What to know about the Winter
Solstice.
1. Dec. 21, shortest day of the
year.
2.Sun at lowest altitude at noon.
3.24 hrs. of darkness at North
Pole.
4.Direct sun ray at 23.5° south

during seasons?
What to know about the Equinox.
1. Sept. 21 and March 21.
2.12 hrs of daylight, 12 hrs of
night.
3.Direct sun ray at Equator.
4.Sun rise – E, Sun set – W.

Is distance important to
seasonal change?
Farthe
st
away
on July
4,
Closest
on
Jan. 3.
Earth’s orbit is an
ellipse.

Reasons for the Seasons Video Clip

Regents Question
Which position of Earth
represents the first day of
summer in the Northern
Hemisphere?
(1)A (3) C
(2)B (4) D

Regents Question
How many degrees will the
Sun’s vertical rays shift on
Earth’s surface as Earth
travels from position C to
position D?
(1)15○
(3) 47○
(2)23.5○
(4) 365○

The Moon
 The Moon is Earth’s only natural
satellite
 It is estimated to be about 4.5 billion
years old

Features
 The Moon’s interior is thought to
have layers, similar to earth
 The Moon’s surface is covered with
craters, caused by meteor impacts.

The Moon’s Surface
 Dark areas called Maria (from Latin
mare, meaning sea). These are
ancient lava flows.
 Light areas are Lunar Highlands,
which are mountain ranges made of
lighter color rocks.

Moon Rocks
 Rocks on the Moon are made of
minerals similar to those on Earth.

Rotation and Revolution
 The Moon’s periods of rotation and
revolution are both 27.33 days. The
result is that the same side of the
Moon always faces Earth (the near
side).
 However, it takes 29.5 days for the
Moon to completely revolve around
the Earth

Why Two More Days?
Moon’s
orbit
Earth
moving
around
Sun.
Earth Moon
Moon has to
revolve for 2
more days to
get back to
the new moon
phase.
This occurs
because the Earth
is revolving around
the Sun.

Phases
 Moon Phases are apparent changes in shape
due to the position of the Moon in its orbit.
 Phase names:
– New
– Crescent
– Quarter
– Gibbous
– Full
 Waxing – becoming more visible
 Waning – becoming less visible

Regents Question
Which sequence of Moon phases could be observed
from Earth during a 2-week period?

because as the Earth
rotates, the moon
revolves

How many hours is the
moon visible each day?
Approximate Times of Moonrise and Moonset
moonrise moonset
new moon 06:00 AM 06:00 PM
waxing crescent 09:00 AM 09:00 PM
first quarter 12:00 PM 12:00 AM
waxing gibbous 03:00 PM 03:00 AM
full moon 06:00 PM 06:00 AM
waning gibbous 09:00 PM 09:00 AM
third quarter 12:00 AM 12:00 PM
waning crescent 03:00 AM 03:00 PM
new moon 06:00 AM 06:00 PM

Moon’s Effect on Tides
 Tides are the periodic rise and fall of
the ocean surface
 Tides are caused by the gravitational
attraction of the Moon and the Sun
on ocean water
 High tide will occur when the Moon is
overhead, as well as on the opposite
side of the Earth.

Tides
Eart
h
High High
Low
Low
Caused by
Moon’s gravity
pulling Earth’s
water.
Two of each
because the
Earth
rotates.
Tides always
High in line
with Moon.

Regents Question
The change in the tides as shown
on the graph is primarily the
result of
(1) Earth’s rotation and the Moon’s
revolution
(2) Earth’s rotation and revolution
(3) The Moon’s rotation and Earth’s
revolution
(4) The Moon’s rotation and revolution

Regents Answer
(1) Earth’s rotation and the Moon’s
revolution

Phases and Tides
 The alignment of the Moon with the Sun
affect tides.
 At the full and new moon phase, both are in
line, causing a higher high tide and a lower
low tide. This is called the Spring Tide.
 At the quarter phases, the Sun and Moon
work against each other, resulting in
weaker tides, called Neap Tides.

Spring and Neap Tides
Eart
h
Earth
Sun
Sun
Neap Tide
Spring Tide
Quarter Phase
– not a large
change from
high to low
tide.
New and Full
Phase – big
change from high
to low tide.

Regents Question
What is the main reason that the
gravitational attraction between
Earth and the Moon changes each
day?
(1) Earth’s axis is tilted at 23.5
○
.
(2) Earth’s rotational speed varies with
the seasons.
(3) The moon has an elliptical orbit.
(4) The moon has a spherical shape.

Regents Answer
(1) The moon has an elliptical
orbit.

Eclipses and Conclusions Video Clip

Eclipses
 An eclipse occurs when the Sun’s light
is blocked from either the Earth or
the Moon.
 Since the orbit of the Earth and the
Moon are along different planes,
eclipses don’t happen frequently.

What’s the
difference between
solar and lunar eclipses?
Earth goes
into moon’s
shadow
moon goes
into Earth’s
shadow

Solar Eclipse
 Solar Eclipse – occurs when the Moon
blocks the Sun’s rays from reaching Earth.
It occurs only at new moon phase.

Solar Eclipse
Penumbra
Umbra
Solar Eclipse Photo

Lunar Eclipse
 Lunar Eclipse – occurs when the Earth
blocks the Sun’s rays from reaching the
Moon. Only occurs at full moon phase.

Lunar Eclipse
Umbr
a
Penumbra
Every one
on the
night side
sees the
eclipse.

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