Transcript Geometry of orbits - Harpursville Middle School

Astronomy
The Universe
Stars
Our Solar System
Orbits
Gravity
20 July 2015
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!

20 July 2015
2
Origin of the Universe

Big bang
Approximately 15 billion years ago
 Started from a single point and has been spreading
outward ever since

20 July 2015
3
Raisin bread analogy of an expanding universe
20 July 2015
4
Organization of the Universe
Universe
Galaxy Cluster
Galaxy
(ex. Milky Way)
Solar System
Star (Sun)
Planet (Earth)
20 July 2015
5
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

20 July 2015
6
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
20 July 2015
7
Page 14 of the ESRT
20 July 2015
8
Electromagnetic Spectrum – humans
can only see one part of spectrum –
visible light
20 July 2015
9
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.
20 July 2015
10
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.
20 July 2015
11
20 July 2015
12
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
•
•
20 July 2015
Longer wavelength
Light shifted toward the red end
of spectrum
13
20 July 2015
14
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
20 July 2015
15
What is the best
inference that can be
made concerning the
movements of
Galaxies A, B, and
C?
20 July 2015
16
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
20 July 2015
17
Hubble Deep Space Galaxies
20 July 2015
18
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!!
20 July 2015
19
The Milky Way: our galaxy
20 July 2015
20
20 July 2015
21
Our solar system is part of the spiral
Milky Way Galaxy
20 July 2015
22
Edge-on view of the
Milk Way Galaxy
20 July 2015
23
20 July 2015
24
Elliptical Galaxy
20 July 2015
25
Spiral galaxy in the constellation Andromeda
20 July 2015
26
Barred Spiral
20 July 2015
27
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

20 July 2015
This is why the Milky Way is brighter in the
winter time
28
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
20 July 2015
29
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)
20 July 2015
30
20 July 2015
31
Which groups of stars are the BRIGHTEST?
20 July 2015
32
Which group of stars is the HOTTEST?
20 July 2015
33
Which groups of stars are the SMALLEST
and DIMMEST?
20 July 2015
34
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

20 July 2015
35
20 July 2015
36
20 July 2015
37
20 July 2015
38
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
20 July 2015
39
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

20 July 2015
Asteroids, meteors and comets
40
The Planets: Two kinds

Rocky (Terrestrial)
Mercury
 Venus
 Earth
 Mars
 Pluto

Jupiter
 Saturn
 Uranus
 Neptune

20 July 2015
Gas Giants


Saturn would float
if you could put it
in water!
41
20 July 2015
42
The Big “E”

Earth is unique

Due to abundant liquid water

20 July 2015
Means life as we know it!
43
Home!
20 July 2015
44
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

20 July 2015
45
20 July 2015
46
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 ???)

20 July 2015
47
Comet Hale-Bopp
20 July 2015
48
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

20 July 2015
49
20 July 2015
50
Terrestrial Planets – Earth largest
solid, smaller, denser
20 July 2015
51
Earth compared to Jovian Planets
gaseous, large, low density
20 July 2015
52
All planets compared to Our Sun
No longer
considered
a planet
20 July 2015
53
20 July 2015
54
20 July 2015
55
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
20 July 2015
56
Kepler’s First Law

circle
20 July 2015
The orbits of
planets around
stars is elliptical
ellipse
57
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
20 July 2015
58
Geometry of Orbits

The major axis is defined by a line that passes through the
two foci (plural of focus)
20 July 2015
59
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
20 July 2015
60
SHAPE OF ELLIPSES
Eccentricity = 0
circle
Eccentricity = 0.5
Eccentricity = 1
20 July 2015
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
20 July 2015
62
20 July 2015
63
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
20 July 2015
64

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
20 July 2015
66
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.
20 July 2015
67
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?
20 July 2015
68
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?
20 July 2015
69
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?
20 July 2015
70
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
20 July 2015
71
Equal Area, Equal Time
20 July 2015
72
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
20 July 2015
73
Orbits
in our
Solar
System
20 July 2015
74