Download Geometry of orbits - Harpursville Middle School

Astronomy
The Universe
Stars
Our Solar System
Orbits
Gravity
22 May 2017
1
The Size of the Universe


Distance in space is often measured in light
years
One light year is the distance that light travels
in one Earth year
Our moon is 1 1/2 light second away
 Our sun is 8 light minutes away
 Our closest star (besides the sun) is 4 light years
away
 The universe is thought to be 25 billion light
years across!

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Origin of the Universe

Big bang
Approximately 15 billion years ago
 Started from a single point and has been spreading
outward ever since

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Raisin bread analogy of an expanding universe
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Organization of the Universe
Universe
Galaxy Cluster
Galaxy
(ex. Milky Way)
Solar System
Star (Sun)
Planet (Earth)
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Galaxies


A huge cluster of stars and other matter is
called a Galaxy
Move
Rotate in place (spin)
 Move away from the center of the universe


Have different shapes
Spiral, like the Milky Way
 Globular
 Ring

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Expansion Evidence for Big Bang

Electromagnetic Energy - Type of energy given
off in the form of transverse waves

Different types of electromagnetic energy are
distinguished by their different wavelengths
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Page 14 of the ESRT
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Electromagnetic Spectrum – humans
can only see one part of spectrum –
visible light
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Expansion Evidence

Most stars are made of Hydrogen & Helium gas.

Elements that emit specific wavelengths within
the electromagnetic spectrum.

The spectral line pattern can be used to identify
the star rather like a fingerprint or bar code.
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Red Shift – Blue Shift
 In
1929, Edwin Hubble observed that spectral
lines emitted by stars in distant galaxies were
considerably Red shifted.
 If
a galaxy or star were moving toward the
earth, the spectral lines would show a blue shift.
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Shifting of Wavelengths is called the
Doppler Effect
•
Change in the wavelength of
light emitted by an object due to
its motion
•
Movement toward “squeezes” the
wavelength
•
•
•
Shorter wavelength
Light shifted toward the blue end
of the spectrum
Movement away stretches the
wavelength
•
•
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Longer wavelength
Light shifted toward the red end
of spectrum
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RED SHIFT – BLUE SHIFT

The greater the degree of shift of the spectral lines, the
faster the object is moving away

The star light DOES NOT appear red or blue (it still
appears as white light from the star)

The “bar code” for each element either shifts to the
shorter wavelength blue end of the spectrum or to the
longer wavelength red end of the spectrum
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What is the best
inference that can be
made concerning the
movements of
Galaxies A, B, and
C?
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Hubble Telescope and Deep Space



The Hubble Telescope was pointed at an area of
“nothing”
The next slide is the image Hubble captured.
Each bright spot is a galaxy, similar to our own
Milky Way
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Hubble Deep Space Galaxies
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Inferences about our Galaxy



Large (as galaxies go): 100,000 ly across
Contains several hundred billion stars
The Milky Way rotates once every 220 million
years

That means we are moving at 250 km per second!!
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The Milky Way: our galaxy
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Our solar system is part of the spiral
Milky Way Galaxy
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Edge-on view of the
Milk Way Galaxy
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Elliptical Galaxy
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Spiral galaxy in the constellation Andromeda
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Barred Spiral
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Our Solar System in the Milky Way:


Is located in an arm on the outer edge of the
Milky Way
We face in to the center of the galaxy in the
winter

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This is why the Milky Way is brighter in the
winter time
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Stars

Fueled by nuclear fusion
When atoms are compressed so hard they “fuse”
 Creates a tremendous amount of energy


Our closest star is the Sun
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Stars



Stars are born, live and die
Classified based on size and temperature
What they become in death can be determined
by the Hertzsprung-Russell Diagram (H-R
Diagram)
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Which groups of stars are the BRIGHTEST?
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Which group of stars is the HOTTEST?
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Which groups of stars are the SMALLEST
and DIMMEST?
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Our Sun



A medium sized star
Makes up 99.86% of the Sloar System’s mass!
Contains sunspots

Storms within the hot gas
Appear as black spots that move across the surface
 Are produced in cycles

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Satellites

Any object that orbits another object in
space is known as a satellite
 Planets
are natural satellites of their stars
 Moons are natural satellites of their planets

We also have artificial satellites which
orbit Earth
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Our Solar System


The Sun is near the center of the Solar System
Satellites in the Solar System:

Rocky planets


Gas giants


Like your home planet
Solid core surrounded by gas
Other stuff

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Asteroids, meteors and comets
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The Planets: Two kinds

Rocky (Terrestrial)
Mercury
 Venus
 Earth
 Mars
 Pluto

Jupiter
 Saturn
 Uranus
 Neptune

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Gas Giants


Saturn would float
if you could put it
in water!
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The Big “E”

Earth is unique

Due to abundant liquid water

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Means life as we know it!
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Home!
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Other Natural Satellites

Asteroids
Chunks of rock and metal that circle the sun Range
in size from hundreds of km to mm
 Most are in a belt between Mars and Jupiter
 Rarely cross Earth’s orbit
 May have caused the extinction of dinosaurs

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Other Natural Satellites

Comets
“Dirty snowballs” from outside the solar system
 Probably provided young Earth’s water
 “Tail” created by vaporization when they approach the
Sun
 Examples:

Halley’s – 76 year orbit (will be back in 2061)
 Hale-Bopp – was near in 1997 (will be back in ???)

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Comet Hale-Bopp
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Other Natural Satellites

Meteors
Small particles pulled into Atmosphere by Earth’s
gravity
 Most burn up in the atmosphere


Shooting stars
If they reach the Earth’s surface are called
meteorites
 Evidence of meteors:

Most is eroded away
 Meteor Crater in Winslow AZ

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Terrestrial Planets – Earth largest
solid, smaller, denser
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Earth compared to Jovian Planets
gaseous, large, low density
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All planets compared to Our Sun
No longer
considered
a planet
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Kepler’s Three Laws of Planetary
Motions
1.
2.
3.
Planets’ orbits’ are elliptical in shape
A planet will move through equal area of space
in an equal amount of time
The farther a planet is from the focus, the
longer the period of revolution
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Kepler’s First Law

circle
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The orbits of
planets around
stars is elliptical
ellipse
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Geometry of Orbits

The orbits of
planets around their
star are elliptical
with the star at one
focus and the
planet’s average
mass at the other
focus
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Geometry of Orbits

The major axis is defined by a line that passes through the
two foci (plural of focus)
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Geometry of Orbits



The word eccentricity
is used to describe
how “out of round” an
orbit is
Eccentricity can be
defined numerically
No units are used in
describing eccentricity
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SHAPE OF ELLIPSES
Eccentricity = 0
circle
Eccentricity = 0.5
Eccentricity = 1
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line
61
Kepler’s Three Empirical
Laws of Planetary Motion
1. The orbital paths of the planets are
elliptical, with the Sun at one focus
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Kepler’s Three Empirical
Laws of Planetary Motion
2. An imaginary line connecting the Sun to
any planet sweeps out equal areas in
equal time..
Area 1
Area 2
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
TO THE HUMAN EYE, MOST ORBITS
OF PLANETS LOOK LIKE CIRCLES

SLIGHTLY ELLIPTICAL SHAPE OF
EARTH’S ORBIT CAUSES THE PLANET
TO VARY THE DISTANCE TO THE SUN
DURING REVOLUTION
147 million
kms.
152 million kms.
This is the best website for 1st and 2nd laws of Kepler
https://solarsystem.colorado.edu/home/lowRes.html
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Geometry of Orbits
The formula for finding eccentricity is:
Eccentricity =
Distance between the foci
Length of the major axis
This formula is found in your ESRTs
***Units must be the same in the numerator and
denominator, then the units cancel and eccentricity is
expressed without units.
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Eccentricity Example
The distance between foci of planet beta’s
orbit is 3000 km. The length of it’s major axis
is 600,000 km. What is the eccentricity of
Beta’s orbit?
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Eccentricity Example
 A comet has a major axis with length
12,000,000 km and foci that are 24,000 km
apart. What is the eccentricity of the comet’s
orbit?
 Which has a more eccentric orbit, the
comet or Beta?
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The Force of Gravity

Earth’s orbit around the sun has an
eccentricity of 0.017 (close to zero)

Therefore the distance between the sun and
Earth changes very little throughout the year
 What is the difference in distance between
the Earth’s nearest approach and farthest
distance from the sun?
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Kepler’s Second Law:
The Force of Gravity


The speed of a planet varies with its distance from the sun
The closer to the sun, the faster the planet travels in its
revolution around the sun
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Equal Area, Equal Time
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Kepler’s Third Law in our Solar System
Use your ESRT to complete the chart below:
Planet
Distance from Sun
Period of Revolution
Mercury
Earth
Mars
Saturn
Uranus
Pluto
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Orbits
in our
Solar
System
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