1. The Universe Stars Our Solar System Orbits Gravity
Astronomy
The Universe
Stars
Our Solar System
Orbits
Gravity
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2. 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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3. 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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4. Raisin bread analogy of an expanding universe
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5. Organization of the Universe
Galaxy Cluster
Galaxy
(ex. Milky Way)
Solar System
Star (Sun)
Planet (Earth)
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6. 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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7. 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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8. Page 14 of the ESRT
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9. Electromagnetic Spectrum – humans can only see one part of spectrum – visible light
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10. 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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11. 4/20/2017
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.
When scientists look at the spectrum of radiation emitted by stars in far away galaxies they noticed the positions of the characteristic wavelengths are shifted to the shorter (blue light end of spectrum) or longer (red light end of spectrum) wavelengths depending on whether the star is coming towards you or moving away.
In 1929, Edwin Hubble observed that spectral lines emitted by stars in distant galaxies were considerably Red shifted.
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©1999 John Culpepper

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13. 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
Longer wavelength
Light shifted toward the red end of spectrum
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15. 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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16. What is the best inference that can be made concerning the movements of Galaxies A, B, and C?
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17. 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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18. Hubble Deep Space Galaxies
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19. 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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20. The Milky Way: our galaxy
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22. Our solar system is part of the spiral Milky Way Galaxy
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23. Edge-on view of the Milk Way Galaxy
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25. Elliptical Galaxy
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26. Spiral galaxy in the constellation Andromeda
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27. Barred Spiral
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28. 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
This is why the Milky Way is brighter in the winter time
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29. Stars Fueled by nuclear fusion Our closest star is the Sun
When atoms are compressed so hard they “fuse”
Creates a tremendous amount of energy
Our closest star is the Sun
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30. 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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32. Which groups of stars are the BRIGHTEST?
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33. Which group of stars is the HOTTEST?
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34. Which groups of stars are the SMALLEST and DIMMEST?
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35. 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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39. 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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40. Our Solar System The Sun is near the center of the Solar System
Satellites in the Solar System:
Rocky planets
Like your home planet
Gas giants
Solid core surrounded by gas
Other stuff
Asteroids, meteors and comets
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41. The Planets: Two kinds Rocky (Terrestrial) Gas Giants
Mercury
Venus
Earth
Mars
Pluto
Gas Giants
Jupiter
Saturn
Uranus
Neptune
Saturn would float if you could put it in water!
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43. The Big “E” Earth is unique Due to abundant liquid water
Means life as we know it!
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44. Home!
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45. 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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47. 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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48. Comet Hale-Bopp
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49. 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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51. Terrestrial Planets – Earth largest solid, smaller, denser
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52. Earth compared to Jovian Planets gaseous, large, low density
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53. All planets compared to Our Sun
No longer considered a planet
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56. Kepler’s Three Laws of Planetary Motions
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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57. Kepler’s First Law The orbits of planets around stars is elliptical
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58. 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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59. Geometry of Orbits
The major axis is defined by a line that passes through the two foci (plural of focus)
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60. 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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61. SHAPE OF ELLIPSES Eccentricity = 0 circle Eccentricity = 0.5
Eccentricity = line
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62. 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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64. 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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65. 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.

66. This is the best website for 1st and 2nd laws of Kepler
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67. Geometry of Orbits The formula for finding eccentricity is:
Distance between the foci
Eccentricity =
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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68. 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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69.  Which has a more eccentric orbit, the comet or Beta?
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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70. The Force of Gravity
Earth’s orbit around the sun has an eccentricity of (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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71. 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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72. Equal Area, Equal Time
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73. 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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74. Orbits in our Solar System
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