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The Final Frontier
1st – Lets get a perspective on how large
and far away things in space are….
Facts: Sun = 109 X larger than Earth
Earth = 3.7 X larger than Moon
Moon = 30 X farther from Earth than Earth’s diameter
Sun = 400 X farther away than Earth is from the Moon
1st – Calculate the diameters of Earth and Sun using a scale in which
the Moon’s diameter = 1 cm
2nd – Use step 1’s answers to calculate the distance between Earth and
Moon, Earth and Sun
3rd – Cut out circles of the correct diameter to represent Earth, Moon,
Sun and glue them down at the correct scaled distance apart.
Astronomers must analyze LIGHT that comes to the Earth
from distant objects in Space
= Electromagnetic Radiation that travels as a wave
Electric and Magnetic disturbances
Wavelength
= distance from two parts on
the wave that are the same (crest-crest/troughtrough)
Frequency (f)= # of waves passing a point in 1
second
All Light travels at the same speed = speed of light = 3.0X108 m/s
Our eyes have only evolved to be able to “see”
VISIBLE light…that’s why we call it visible!
Not all light coming from space is visible, and its so far
away its hard for our eyes to see…therefore, we use
TELESCOPES to see these different forms of light
Telescopes
Detect different wavelengths of light
Collect more light than our eyes are able to (larger openings)
Can collect light over periods of time = create photographs that
allow us to observe changes out in space
Focus light at a point where an image can be studied (our eyes
do this too, but only with visible wavelengths)
Largest observatory in Hawaii – Mauna Kea
We also send SATELITES and PROBES into space to collect information
Why??
Our atmosphere blocks certain wavelengths of light (IR, UV,
X ray, Gamma) so it doesn’t allow us to study everything coming
from space
Our atmosphere also blurs images because it doesn’t allow
all wavelengths to pass
Break down of Space
Universe
All existing matter and space
AKA: The Cosmos
Galaxy
System of millions or billions of stars with gas and dust held
together by gravitational attraction
We live in the Milky Way Galaxy
Solar System
Collection of planets and their moon in orbit around a sun
Also contain smaller bodies (asteroids, meteoroids, comets)
How did it all begin…or did it even have a
beginning??
1930-1965…the scene: debating astrophysicists…aka: largest nerds on the planet
2 Theories have Emerged to explain the beginning of our Universe
Big Bang Theory
Proposed by George Lemaitre (a
priest, astronomer, and Prof. of
Physics)
States that the universe orginated
when a “primeval cosmic egg”
exploded
Universe has been expanding ever
Steady – State Theory
Proposed by Fred Hoyle, Herman
Bandi, and Tommy Gold
Stated that the Universe looks the
same from all points and has not
changed
-There was no beginning
-Matter is continuously created to fill
space left behind as universe expands
Major Points of Debate that eventually lead to an accepted theory
Religion’s Part
Pope Pious XII, 1952 – announces that the Big Bang Theory affirms the
idea of a creator, thus this theory was in harmony with Christianity
Steady-State becomes associated with Atheism and the Communist Party
because it says there was no beginning
Major Points of Debate that eventually lead to an accepted theory
Miscalculations Early On
A miscalculation within the Big Bang Theory showed that our solar system
was older than our universe…this caused some doubt in the theory early
on
This was later figured out and fixed – new calculations showed
the universe as 2X as old as the solar system
Nail in the Steady-State Coffin…
Cosmic Microwave Background Radiation
is discovered!
Cosmic Microwave Background Radiation……..
What tha heck is that?!
Faint glow of light
that fills the Universe
Falls on Earth from
all directions, at all
times, with the same
intensity
Residual heat from the
creation of the
Universe…afterglow of
the Big Bang
(Its like heat that
comes off of a sun
warmed rock at night)
Oldest light we can pick up = Shows us the farthest back in time…14 byo
From a time when the Universe wasn’t cold and dark…it was a firestorm of
radiation and elementary particles which these later form the planets & galaxies
As the Universe was stretched through
expansion… so were the wavelengths of
the light from the explosion…currently is
has stretched to the size of
MICROWAVES and cooled to a
temperature of 2.73oK
Cosmic Microwave Background Radiation Discovery
The Hulmdel Horn Antenna, 1960s, New Jersey
Big Bang Theory Details
Nothing left (that we know of) from before the Big
Bang…so don’t ask what happened before…no one
knows!
The idea begins with Hubble’s Discovery, 1939 – the
Universe is moving away…expanding in all directions
taking galaxies with it = Hubble’s Law
 Thus, in reverse thought, the Universe
must have been much smaller in the past
 It was a tiny point in existence
All matter/energy existed within this small point
 Eventually too dense = explosion of the
Universe
Evidence:
1) Expansion of the Universe is seen
2) Cosmic microwave background radiation
3) Abundance of different elements were predicted and are
now found (Hydrogen, Helium)
4) Lays a framework for evolution of the Universe seen today
Evolution of the Universe…What can we expect?
Within the Big Bang Theory, we know that there are two
forces acting on the Universe
Outward Momentum
of Expansion
Inward Pull of Gravity
If this force is greater
than the outward
If this force is greater than
momentum = expansion
the pull of gravity =
stops, universe starts to
expansion will never stop =
contract = Closed
Open Universe
Universe
If the Forces are Equal = Expansion will slow, but
contraction won’t happen = Flat Universe
Most recent discoveries show that the expansion is SPEEDING UP…a force is
required to make this happen
Formation of the Milky Way Galaxy
Starts as a spherical
cloud
Cloud collapses due to
gravity
Rotation forces the
cloud into a disc shape
Formed 13.5 BYA
Galactic Center is surrounded by a Nuclear Bulge, surrounded by a
halo = oldest stars
Disk sticks out from the Bulge = Youngest stars
4 Major Spiral Arms (several minor arms) – our sun is in a minor
arm
Formation of Our Solar System
Formed 4.5 BYA
Interstellar cloud = clouds made of gas/dust that exist in between stars
An interstellar cloud started to condense as a result of gravity
This led to the formation of a star and planets
Collapse starts slow, then accelerates
If the cloud is rotating, this will cause it
to spin faster until it contracts
As it collapses, rotation slows, cloud
flattens = Becomes a rotating disk with
a dense center
Formation of our Sun
Starts from a SOLAR NEBULUA (disk of gas and dust)
The dense concentration of hot gases at the center of the
nebula became our sun
Formation of our Planets
The disk of gases surrounding the sun has various
temperatures – hottest closest to the sun, coldest
furthest from the sun
As the gas cools, different substances (elements) are able to
condense into liquids and solids
The condensing liquids/solids begin to clump together and
grow into larger bodies called Planetesimals
Planetesimals collide and some clump together forming
larger bodies = Planets
The Sun
Largest object in our solar system (99% of the
mass…109 Earths to fit across it!)
Because it’s the largest, it has the largest
gravitational force and thus it controls the
motions of all other objects in the solar system
The Sun’s Fuel Source
The sun’s energy comes from the process
of FUSION
This is the combination of light nuclei,
like hydrogen
Once combined, they form larger
nuclei, like Helium
Mass is LOST!...because it is converted
into ENERGY during the process!
Fission is the opposite of this process…LARGE
E = mC2
NUCLEI ARE SPLIT APART by a NEUTRO,
producing SMALLER, MORE STABLE NUCLEI
We use it in nuclear bombs and nuclear
power plants to make energy.
Structure of the Sun
Core
the temperature at the core is 15,000,000°C
it is made up entirely of gas
Radiation Zone
the temperature in the radiation zone is
2,500,000°C
Convection Zone
the temperature in the convection zone is
1,000,000 °C
Atmosphere of the Sun
There are 3 layers in the Sun’s Atmosphere
Photosphere
• the temperature is 5800 °K
• it is considered the surface of the sun
• it appears yellow in color = where most light is emitted
Atmosphere of the Sun
Chromosphere
•
the temperature is 30,000 ° K
•
it appears reddish in color
•
only visible to the naked eye during a solar eclipse when the
photosphere is blocked
•
can be viewed with the use of special filters to block all
wavelengths of light except for red coming from the sun
Atmosphere of the Sun
Corona
•
the temperature is 1-2,000,000 oK
•
it can only be seen during a total solar eclipse or with use of filters
•
appears white in color
•
flows outward @ high speeds and forms SOLAR WINDS
Solar Winds
Solar Wind: electrically charged atomic particles (IONS) that stream out
into space from holes in the corona
•
As particles fly past the Earth, they interact with our magnetic
field and upper atmosphere = These are called VAN ALLEN BELTS
•
This collision with gases creates LIGHT = CALLED AURORAS
The Sun’s Atmosphere CHANGES over time
Changes in the sun’s atmosphere creates SOLAR ACTIVITY
Solar Activity occurs on an 11 yr cycle
SUNSPOTS = dark spots seen on the
Sun’s surface
-Actually very bright. Appear dark
because surrounding areas are much
cooler
-Created when the Sun’s magnetic field
pokes thru the photosphere
-Typically last 2 months
-Occur in pairs
-Pairs have opposite magnetic poles
The Sun’s Atmosphere CHANGES over time
Changes in the sun’s atmosphere creates SOLAR ACTIVITY
Prominences: cloud of glowing gases that arches high above the sun’s surface
•
caused by the sun’s magnetic field
The Sun’s Atmosphere CHANGES over time
Changes in the sun’s atmosphere creates SOLAR ACTIVITY
Solar Flare: sudden outward eruption of electrically charged atomic particles
Associated with sunspots
May interfere with phone, TV, and radio reception
Effects of Solar Activity on the Earth
Scientists have evidence that solar activity affects our CLIMATE
There are subtle climate variations within 11 yr periods – these correspond to
the 11 yr cycles of solar activity
Ex: Little Ice Age of the 1600s
- Solar Activity stopped, no sunspots for
nearly 60 yrs
- Severe weather changes on Earth
- Earth experienced a mini Ice Age –
weather was very cold in Europe and North
America during these years
Energy from the Sun
Amount of energy reaching the Earth from the Sun every day is ENORMOUS!
1354 J of Energy is received above the Earth’s atmosphere in 1 m2 /s…
in other words:
Thirteen 100-W lightbulbs could be operated with the
energy that strikes a 1-m2 area
Not all of this reaches the ground – some is absorbed and scattered
by our atmosphere – this helps to PROTECT us!
The Planets in our Solar System
Terrestrial Planets
-
4 inner planets
All close to the size of Earth
All are solid and rocky
Mercury, Venus, Earth, Mars
Gas Giants
- 4 outer planets
- Larger
- All are gaseous and lack solid
surfaces
- Jupiter, Saturn, Uranus, Neptune
Other Debris in our Solar System
Asteroid Belt
- Debris/planetisimals
trapped between Jupiter
and Mars
- Held here because of the
gravitational force
between the planets
Asteroids = Left over debris from the
formation; range in size
Meteoroids = pieces of asteroids that fall to
Earth
Meteor = Meteoroid that
burns up in Earth’s
atmsophere
Meteorite = Part of the meteor that
reaches the surface of the Earth; Can
leave an impact crater
Comets = Small, icy bodies that orbit the Sun
-2 clusters/clouds of comets in our system: Kuiper Belt and Oort Cloud
Haley’s Comet
- Orbits into the inner
system periodically
(every 76 yrs)
- Next time = 2061
Meteor Showers
- Occur when Earth intersects the orbit
of a comet
- The comet burns up in our upper
atmosphere
- Ex: Hale-Bopp - 1997
Movement of the Planets in our Solar System
Early Ideas
“Earth Centered” or Geocentric Model
Astronomers thought that the Sun and
all other planets as well as stars orbited
a stationary Earth
Why did they have this idea??
When observing from the Earth, planets
change their position each night
relative to the stars…which made it
seem like these were all moving around
the Earth
This couldn’t explain why the
normal direction of planet motion
sometimes changed
Retrograde Motion = when planets move in the opposite direction across the
sky.. This happens because these planets are moving around the Sun
slower than the Earth
Nicolaus Copernicus suggested that
the Sun was at the center of the solar
system and this helped to explain
retrograde motion of the planets
Heliocentric
model
Kepler’s 1st Law
Johannes Kepler demonstrated that each planet orbits the Sun in the shape of an
ECLIPSE…not a circle…more like an OVAL
An Elliptical orbit is centered on 2
points…not just 1
Each planet’s elliptical orbit is different in size/shape
These points = Foci
The Sun is always 1 of the focus points
Major Axis = the line between the foci
that represents the maximum diameter
of the ellipse
Half the length of the major axis
= Semimajor axis
Perihelion = closest to the Sun
Aphelion = furthest from the
Sun
Planets distance from the Sun changes
with an Elliptical orbit
Eccentricities
The shape of an ellipse is determined by the distance separating the two foci.
When the foci are close together, the ellipse is "rounder". When they are
farther apart, the ellipse is "flatter". The shape of the ellipse is referred
to as its "eccentricity"
Flatter ellipses are said to
have a "high eccentricity".
Rounder ellipses are said to
have a "low eccentricity".
The eccentricity of any ellipse can be mathematically calculated
and can range from 0 to .999. Low values correspond to ellipses
with low eccentricities….which means they are more
CIRCULAR
Most planets in our Solar System
have low eccentricities…less than 0.93
Comets tend to have high
eccentricities ….closer to 1
Practice Questions
Is the orbit illustrated in the figure representative of the orbits of planets in our solar
system?
No, this show high eccentricity, therefore this
is more representative of a comet
Describe the shape of an ellipse with an eccentricity of 0.
A circle
Why does the fact that the Earth is at perihelion in January prove that the distance of the
Earth from the Sun is not the cause of the seasons?
The eccentricity of the Earths orbit is very low so the difference between
perihelion and aphelion is not very great. Also in January although it is winter
in the northern hemisphere it is summer in the southern hemisphere.
Kepler’s 2nd Law
An imaginary line between a Sun-Planet sweeps out EQUAL amounts of AREA in
EQUAL amounts of TIME
Kepler’s 3rd Law
Mathematical relationship between the SIZE of a PLANETS ELLIPSE (a) and its
ORIBITAL PERIOD (p)
2
3
p =a
p = time in Earth yrs
a = semimajor axis of oribital ellipse…length in AU
In words, this means that as a becomes larger (the orbit is larger), then P
becomes larger too. You would expect this. A planet in a larger orbit has
further to go, so it should take longer, even if it goes at the same
speed
Gravity and Orbits
Isaac Newton observed the Moon’s motion, the planets’ orbits, and how object
accelerate to Earth when falling…
Realized that any 2 bodies will
attract each other with a force
dependent on the objects’
masses and the distance
between them
Called Law of Universal Gravitation
Force = G (m1 m2)
r2
G = gravitational constant = 6.6736 X 10-11 m3/kg/s2
M = mass
r = distance between objects
Basically states: Force of Gravity (attraction) between
objects is directly proportional to the product of the
objects’ masses and inversely proportional to the square
of their distances
Practice Problems
1. If one doubles the distance between two bodies, what happens to the
gravitational attraction between them? Does it increase or decrease? By how
much?
If the distance between two bodies is increased, the
attraction will decrease. If distance (d) is doubled, the
attraction (F) will decrease fourfold (2^2 = 4).
2. If you reduce the distance between two bodies, what happens to the
gravitational attraction between them? Does it increase or decrease? By how
much?
If the distance is halved, the gravitational attraction between the
two bodies would increase fourfold. (2^2 = 4).
3. If you double the mass of one of the two bodies, what would happen to the
gravitational attraction between them?
Gravitation attraction (F) between two masses (M and m) is directly proportional to
the product of their masses. If one of the masses is doubled, the product of the two
masses is doubled and therefore the attraction between them is doubled.
4. Communications satellites orbit the Earth at a height of 36 000 km. How far
is this from the centre of the Earth? If such a satellite has a mass of 250 kg,
what is the force of attraction on it from the Earth?
Center of Mass
Each planet orbits a point between it and the Sun = Center of Mass
AKA: Balance point between the 2 objects…like a see-saw
Heavier objects will be closer to the
balance point
Smaller objects will be further from the
balance point
Earth – Moon – Sun System
Daily Motions we Observe
Sun, Moon, Stars rise and set every day
Rise in the EAST, Set in the WEST
These are the result of Earth’s ROTATION…1/day or 15o/hr around its axis
Earth – Moon – Sun System
Earth’s Rotation
Earth spins around in an imaginary axis as it orbits the sun…orbiting = revolution
2 ways we know Earth rotates:
Foucault Pendulum
Pendulum swings in
constant direction
As Earth rotates, it will
knock over pegs around a
circle
Coriolis Effect
Flowing air and water
are diverted in a N-S
and E-W direction
Earth – Moon – Sun System
Annual Motions we observe
Things that change over the course of a year: Weather, Day length, Temps
These are a result of Earth orbiting the Sun with a Tilted Axis
Earth orbits Sun on
an imaginary plane
called the Ecliptic
It is tilted 23.5o relative to the
ecliptic
1 point of the Earth is tilted toward the Sun while the other point is tilted away.
This will change as the earth revolves….creating the SEASONS
This causes the Sun’s altitude to change
Ex: Highest in the sky in the Northern
Hemisphere during summer; lowest during
winter.
Earth – Moon – Sun System
The Seasons
Vernal Equinox = Spring
March 21st
Axis not pointed @ Sun – both Hemispheres get
equal Sunlight. Sun is overhead @ Equator
**Day and Night are Equal
Winter Solstice
Summer Solstice
In N. Hemisphere, Sun is
highest in the sky –
directly overhead @
Tropic of Cancer (23.5o
N Lat)
**Max amount of
daylight – June 21st
**Sun doesn’t set @ Artic
Circle/Doesn’t rise @
Antarctic Cirlce
Autumnal Equinox = Fall
September 21st
In N. Hemisphere,
Sun is lowest in
the sky – directly
overhead @ Tropic
of Capricorn
(23.5o S Lat)
**Min amount of
daylight – Dec 21st
**Sun doesn’t set @
Antarctic
Circle/Doesn’t rise
@ Artic Circle
Earth WOBBLES…like a toy top…while spinning on its axis
Called Precession
Happens because the
Earth is pulled to the
side by the Moon’s
gravitational force
It takes approx. 26,000 yrs
for the Earth to go thru 1
cycle of precession
Phases of the Moon
Lunar Phases = Changes in the appearance of the Moon
The Moon doesn’t produce
light…it reflects light from
the Sun
When Moon is in between
the Earth and Sun, we can’t
see it b/c Sunlit side is away
from us!
Waxing = Amount of Sunlight
reflected from Moon is
INCREASING
Waxing Cresent =
less than half of
Moon is seen
1st Quarter Moon = Between phases – Half of Moon is
seen
Waxing Gibbous =
more than half of
Moon is seen
Phases of the Moon
Waning = Amount of Sunlit side is DECREASING
Waning Cresent =See LESS than
half of sunlit side
Waning Gibbous = See MORE
than half of the sunlit side
Full Moon = Earth is between
Moon and Sun…so we see entire
Sunlit side of the Moon
3rd Quarter Moon = Half of Moon is
seen
Lunar Month = Time to go through a complete cycle of phases ~ 29.5 days
Takes 27.3 days to revolve around Earth…so the Moon Rises/Sets 50 min later each day
b/c it has moved 13o in 24 hr..Earth has to turn an extra 13o each day!
The Dark Side of the Moon
The Moon has SYNCHRONOUS ROTATION = its ORBITAL and ROTATIONAL
periods are the same…it spins at the same speed it orbits – so spins around 1
time as it goes around the Earth
So..we only ever see 1 side of the moon…we never get to see the dark side
How does the Moon Affect the Earth?
Moon’s Gravity pulls on the Earth and CREATES BULGES of ocean water on
the near and far sides of the Earth
As Earth rotates, BULGES STAY ALIGNED WITH MOON…so person on
shoreline sees ocean rise/fall every 12 hours…These are called TIDES
Spring Tides = higher than normal b/c Sun and Moon are
aligned in same direction – so both pull on Earth
Neap Tides = lower than normal b/c Sun and Moon are @
Right angles to each other
Solar Eclipses
Happen when the Moon passes directly between the Sun and Earth and it
BLOCKS our view of the Sun
(Sun and Moon appear the same size b/c Sun is so far away)
Umbra = Moon’s shadow with
no direct sunlight
Small portion of viewers falling in the Umbra see a
TOTAL Solar Eclipse…no light
Penumbra = Moon’s shadow
with some direct sunlight
Larger portion of viewers falling in the Penumbra
see a PARTIAL Solar Eclipse
Solar Eclipses
Why don’t we see a Solar Eclipse each Month?
Moon is tilted 5o
relative to ecliptic
plane…so it usually
passes North or
South of the Sun
rather than directly
in line with it!
Moon’s Distance from the Earth Changes as it moves
Perigee = Closest = Moon appears Larger
Apogee = Farthest = Moon appear Smaller
When in Apogee, can’t completely block Sun during an
Eclipse = Annular Eclipse b/c you see a Ring from Sun
around Moon = Annulus
Lunar Eclipses
When Moon passes through Earth’s Shadow
Only @ time of a Full Moon, when Moon is in opposite direction from Sun
If Moon falls in Earth’s Umbra = Total Lunar Eclipse
If Moon falls in Earth’s penumbra = Partial Lunar Eclipse
Solar and Lunar Eclipses occur in almost equal #s w/ slightly
more Lunar Eclipses…Max = 7/yr which last happened in 1982
and won’t happen again until 2038