The document discusses the history of astronomy from ancient to modern times. It begins by explaining how early civilizations used the movement of stars, planets and the moon to tell time before modern clocks. It then discusses key figures like Ptolemy who proposed an Earth-centered model, Copernicus who proposed a Sun-centered model, Galileo who used a telescope to observe moons orbiting Jupiter which supported Copernicus, and Kepler who formulated laws of planetary motion. The document also discusses constellations, stars, and life cycles of stars of different masses.

2. Imagine that it is 5,000 years ago. Clocks and
modern calendars have not been invented. How
would you tell time or know what day it is?
One way to tell the time is to study the movement of
stars, planets and the moon. Studying the ancient
skies was so important that ancient people built
observatories.
Over time, the study of the night sky became the
science of Astronomy. Today Astronomy is known as
the study of the universe.

3. Who’s Who of Early Astronomy
 The careful work of early
astronomers helped people
understand their place in the
universe. Almost everything early
astronomers knew about the
universe came from what they
could discover with their eyes and
minds.
 Not surprisingly, most early
astronomers thought that the
universe consisted of the sun, the
moon and the planets. They
thought that the stars were at the
edge of the universe.

4. GEO
MEANS
EARTH

5. There have been 2 main
thoughts about how the solar
system and universe are set up:

6. Ptolemy:
An Earth-Centered Universe
 A Greek Astronomer-around 100 AD
 Ptolemaic Theory-he wrote a book that combined all of
the ancient knowledge of astronomy that he could find. He
then expanded on it with careful mathematical
calculations.
 Ptolemy thought that the Earth was at the center of the
universe and that the other planets and the sun revolved
around the Earth.
 Although his theory was incorrect, it predicted planetary
motion better than any other theory at the time.
 His theory was the most popular for the next 1,500 years.
(Geocentric Theory)

7. Geocentric System:
Ptolemy:
’Improved’ the model…to explain zig zag of
objects in night sky.
Put planets/stars going in circles while orbitting.

8. Geocentric System:
Definition:
earth centered model of the universe .

9. Geocentric System:
The Greeks:
• 4th century BC - Plato and Aristotle wrote about it.

10. Heliocentric System:
Definition:
sun centered model of the solar system

11. Heliocentric System:
Copernicus:
introduced his idea in 1543 - the same year he died

12. Nicholas Copernicus:
A Sun-Centered Universe
•A Polish astronomer (1543)
•Revolutionized astronomy with his new theory
•Heliocentric theory-the sun is at the center of the
universe, and all of the planets, including the Earth,
orbit the sun.
•The theory correctly explained the movement of the
planets around the sun but it did not replace Ptolemy’s
theory immediately.
•When Copernicus’s theory was accepted, major
changes in science and society were taking place.

13. Why do you suppose most
people did not believe
Copernicus’ idea?

14. FINALLY!!
Evidence that supports the heliocentric model is
discovered by…
…a scientist named GALILEO.
1600’s Italian Astronomer
1st to use a telescope

15. What is the evidence that was discovered using the
telescope?
1. There were 4 moons orbiting around Jupiter (not
Earth)
2. Venus went through phases like our moon.

16. Brahe and Kepler
• Mathematicians who made observations on the
shape of the planet’s orbits over a 20 year
period.
• Brahe’s observations and Kepler’s analysis
revealed that the orbits of the planets WERE
NOT PERFECT CIRCLES, but ELLIPSES.
Who else helped?

17. Tycho Brahe: A Wealth of Data
•Danish astronomer, late 1500’s
•Used several tools to make the most detailed
astronomical observations that had been recorded to
date.
•Brahe favored a modified version of Ptolemy’s
theory; the sun and the moon revolved around the
earth and that other planets revolve around the sun.
•While his theory was not correct, Brahe recorded
very precise observations of the planets and stars
that helped future astronomers.

18. Johannes Kepler:
Laws of Planetary Motion
•Was Brahe’s assistant-continued the work after Brahe’s death
•1609-after much analysis of the Brahe’s data, Kepler concluded
that all of the planets revolve around the sun in elliptical orbits
and that the sun in not the exact center of the orbits.
•Stated his ideas in three laws of planetary motion:
1-the sun is the center of universe and the planets revolve
around it in elliptical orbits.
2-the planets move faster when their orbits bring them closer
to the sun.
3-a mathematical formula used to determine the distance of a
planet from the sun.
•These laws are still used today.

19. Galileo: Turning a
Telescope to the Sky
•In 1609, Galileo Galilei became one of the first
people to use a telescope to observe objects in space.
•He discovered craters and mountains on the Earth’s
moon, four of Jupiter's moons, sunspots on the sun,
and the phases of Venus.
•These discoveries showed that the planets are not
“wandering stars” but are physical bodies like the
Earth and it gave him proof that the planets did indeed
revolve around the sun, as Copernicus had stated.

20. Isaac Newton: The Laws of Gravity
•In 1687, Isaac Newton showed that all objects in the
universe attract each other through gravitational force.
•The force of gravity depends on the mass of the objects
and the distance between them.
•Newton’s law of gravity explained why all of the planets
orbit the most massive object in the solar system---the
sun.
•Newton once said that “I could see so far because I
stood on the shoulders of giants.” He gave credit the
observations and ideas of all the scientists who came
before him.

21. Modern Astronomy
 The invention of the telescope and the
description of gravity were two milestones
in the development of modern astronomy.
 In the 200 years following Newton’s
discoveries, scientists made many
discoveries about our solar system. But
they did not learn that our galaxy has
cosmic neighbors until the 1920’s.

22. Edwin Hubble: Beyond the Edge of
the Milky Way
•In 1924, Edwin Hubble proved that other galaxies existed
beyond the edge of the Milky Way.
•His data confirmed the beliefs of some astronomers that the
universe is much larger than our galaxy.
•Today, larger and better telescopes on the Earth and in space,
new models of the universe, and spacecraft help astronomers
study space.
•Computers help process data and control the movement of
telescopes.
•These tools have helped answer many questions about the
universe, yet new technology has presented questions that were
unthinkable even 10 years ago.

24. Ptolemy: Geocentric
Earth-Centered Universe

25. Copernicus: Heliocentric
Sun-Centered Universe

26. Kepler: Heliocentric with Elliptical
orbits

27. Theories of the Universe

28. Galileo: Telescope

29. Constellations & Stars

30. I. Constellations
 Group of stars that
appear to form a
pattern in the sky.
 88 recognized by
International
Astronomy Union

31. A. Zodiac
 Band of 12 constellations along
the ecliptic.

32. B. Ecliptic
 – the plane of the Earth’s orbit
around the sun
 The apparent path that the sun
(and planets) appear to move
along against the star
background.

33. Ecliptic

34. C. Circumpolar
Constellations
 Can be seen all year long
 Never fully set below the horizon
 Appear to move counter clockwise
around Polaris
 Caused by Earth’s Rotation

35. Circumpolar Constellations

36. Star Trails

37. Examples of Circumpolar
Constellations
1. Ursa Major – The Big Bear
2. Ursa Minor – The Little Bear
3. Cassiopeia – Queen on Her Throne
4. Draco- The Dragon
5. Cepheus- The King

38.  # of stars seen as circumpolar depends on
the observers latitude
 Further North the observer lives, the more
stars will appear circumpolar
 Earth turns west to east
 Sky appears to turn east to west

39. D. Ursa Major
 Best known constellation
 Common name is Big Dipper
 Pointer stars- front 2 stars of the Big
Dipper which point to Polaris (North Star)

40. II. Seasonal Changes in
Constellations
 Big Dipper
 In Fall: Low over northern horizon
 Spring: High overhead
 Cassiopeia
 In Fall: Straight overhead
 Spring: Low over northern horizon

41. Seasonal Change & Nightly
change of the Dippers

42. III. Summer Constellations
 1st 3 bright stars that rise form the
Summer Triangle
1. Vega- in Lyra the Harp
2. Altair- in Aquilla the Eagle
3. Deneb – in Cygnus the Swan (Northern
Cross)

43. Summer Triangle

44. IV. Most Famous Winter
Contellation
 Orion Contains:
1. Betelgeuse (Bet el jooz)
a bright red super giant
star found forming
Orion’s right shoulder
2. Rigel – a blue super
giant: 7th brightest star
in the nighttime sky

46. 3 Stars of Orion’s Belt
 Can be used to find 2 other
constellations & a star cluster
1. Canis Major- (Big Dog)
follow the line made by
the 3 stars of Orion’s belt
down to the left
–Sirius- the brightest star in the
nighttime sky is found in Canis Major

47. 2. Taurus (the Bull)
 Follow the line made by Orion’s belt up &
to the right
 Aldebaran- Red star that is the eye of the
bull is the 13th brightest in the nighttime
sky

48. 3. Pleiades Star Cluster (7 sisters)
 Follow the line made by Orion’s belt up
to the right, go through Taurus to a
clump of stars to the right.
 Called Subaru in Japan – means “Unite”

49. V. Kinds of
Stars
A. Red Giant - large red star at
least 10x diameter of the
sun
○ Old Stars
○ Ex. Aldebaran
○ The sun will swell into
a Red Giant when it is
old

50. B. Super Giant
 Largest of all stars 100x more luminous
 Explode as a Super Nova
 Can form Black Holes
 Ex. Betelgeuse, Rigel, Polaris

51. C. Dwarf Stars
1. Less luminous
2. Very dense, mostly carbon
3. Tightly packed nuclei
4. Remains of a red giant that ran out of fuel
5. 1 cup full of star =20 tons or 5 elephants.
6. Most are red/orange/yellow
7. White dwarf is the exception to the color
8. Sun is a yellow dwarf

54. Size Comparison of
Various Stars

55. VI. Variable Stars
 Change in brightness over regular
periods of time
 Ex. Cepheid Variables/Pulsating Stars
Binary Stars & Eclipsing Binary Stars

56. A. Cepheid Variables/
Pulsating Stars
 Change in brightness as they expand &
contract
 Unequal balance between gravity &
nuclear fusion
 Ex. Polaris, Betelgeuse

57. B. Binary Star Systems
 Two stars of unequal brightness revolving
around a center point
 Ex. Algol & its companion star in Perseus

58. C. Eclipsing Binary Stars
 Two close stars that appear to be a single
star varying in brightness.
 The variation in brightness is due to one
star moving in front of or behind the other
star.
Occurs because we see
the system on edge
instead of from above or
below

59. VII. Pulsars or Neutron
stars
A. Discovered in 1967 (LGM)
B. A distant heavenly object that emits rapid
pulses of light & radio waves
C. Formed when a Super Giant collapses;
Protons & Electrons are forced so close
together that they fuse and form only
neutrons

60. Twinkle Twinkle Little Star
"Twinkling Stars" are due to
Earth's atmosphere

61. VIII. Life Cycle of a Medium
Mass Star
1. Nebula
2. Protostar
3. New/Stable State Star
4. Red Giant
5. Planetary Nebula
6. White Dwarf
7. Black Dwarf

62. 1. Nebulae (Plural of
Nebula)
 Space gas seen as faint glowing clouds
 Mostly hydrogen
 Star dust is extremely small, smaller than
a particle of smoke & widely separated,
with more than 300 ft. between individual
particles.
 Nebulae still hinder star gazing because
they absorb light which passes through
them.

63. Types of Nebulae
 Diffuse Nebula - gases glow from stars
w/in them
Ex. Nebula
found in
Sagittarius

64. Types of Nebulae
 Dark Nebula - nebula
not near a bright star
 Ex. Horse Head
Nebula in Orion

65. 2. Protostar
 Shrinking gas balls, caused by a swirl of
gas forming dense areas.
 The gravity of the dense swirl in turn
attracts nearby gases so a ball forms.
 Nuclear fusion occurs & Helium is formed
from Hydrogen
 A new star is born in our galaxy every 18
days

66. 3. Stable State Star
 Star that releases energy in enough force
to counter balance gravity
 Star stops contracting
 Also known as a main sequence star
 Ex. Sun

67. 4. Planetary Nebula
 The outer layers of the Red Giant puff out
more and more.
 The star loses gravitational hold on its
outer layers and they get pushed away by
the pressure exerted from solar winds

68. Planetary Nebula

69. 5. White Dwarf
 Fuel is used up
 No nuclear fusion
occurring
 Remaining heat
radiates into space

71. IX. Life Cycle of a Massive
Star
1. 1st three steps are similar
2. Super Giant
3. Super Nova
4. Neutron Star / Pulsar
5. Black Hole

72. 1. Super Giant
 Rare stars, largest of all
 100x more luminous
 Only stars with a lot of mass can
become super giants
 Some are almost as large as our entire
solar system
 Ex. Betelgeuse & Rigel

73. 2. Super Nova
 Explosion from a massive Super Giant
 Outer layer blasts away at end of Life
Cycle
 Emits light, heat, X-rays, & neutrinos
 Leaves behind a neutron
star or black hole

74. 3. Neutron Star/ Pulsar
 The remains of a super nova
 Very small, super-dense star which is
composed mostly of tightly-packed
neutrons
 Rapidly spinning leftovers of a star
 Emits energy in pulses

75. 4. Black Hole
 Occurs when a star's
remaining mass is
greater than three
times the mass
of the Sun
 Star contracts tremendously
 Incredibly dense with a gravitational field so
strong that even light cannot escape.

76. Life Cycle of a Massive Star

77. X. Distance to stars
A. The Sun is closest star to Earth
B. Takes light 8 minutes to reach Earth
C. Avg. distance:150,000,000Km = 1
AU distance from Earth to the Sun
D. Next nearest star is Proxima
Centauri 4.2 light years away; it can
only be seen in the southern
hemisphere

78. E. Light year
 The distance light has traveled in
a year
 9.5 x 1012 Km/yr
 Speed of light 300,000 Km /sec

79. XI. Physical Properties of
Stars
A. Nuclear fusion supplies the energy
for stars
 Huge size & mass of a star means
outer layers press inward w/
tremendous pressure
 Hydrogen ignites
 Star becomes a huge nuclear bomb
 Hydrogen nuclei combine to form
Helium

80. B. Color of star depends on
surface temp.
1. Blue - hottest stars
Ex. Rigel in Orion; Vega in Lyra;
Sirius in Canis Major
2. Yellow - medium stars ex. Sun
3. Red - coolest stars
Ex. Betelgeuse in Orion, Antares
the heart of Scorpio, Aldebaran in
Taurus

81. C. Star size
-Varies, large range
Smallest can be
smaller than Earth
Largest may be 600,000,000 x Earth.

82. D. The Sun
 is an average star
 yellow in color
 300,000 x the
mass of Earth

83. XII. Luminosity
 Brightness of a star
 Depends on size & temperature
 Hertzsprung-Russell Diagram graphs
Absolute Magnitude (or Luminosity) vs.
Temperature of stars
 Shows the life cycle of stars

84. Hertzsprung-Russell
Diagram

85. A. Absolute Magnitude
 Measure of the amount of light it actually
gives off if all stars were placed a distance
of 32.6 light years away
 Lower # means brighter star
 Negative #’s are the brightest
 Ex. Sun = 4.75 Sirius = 1.4 Rigel = –7.0
Rigel’s the Brightest of the 3 listed if all were
lined up next to each other.

86. B. Apparent Magnitude
 A measure of the amount of light received on
Earth
 Stars below 0 are brightest
 Each magnitude differs by 2.5
 1st magnitude is 100 x brighter than 6th
magnitude
 Ex. Sun = – 26.8 Sirius = – 1.45
Full Moon –12 .6 Rigel = .11
 Sun is the brightest in our sky.

87. XIII. Galaxies
 Systems containing millions or billions of
stars, gas, & dust held together by gravity
Ex. Milky Way
 There are great distances between
galaxies
 The Milky Way belongs to a group or
cluster of galaxies called the local group

88. Spiral Galaxy Like the Milky
Way

89. Three major classes of
galaxies:
1. Elliptical - shaped like large
ovals or football shape
2. Spiral - pinwheel shaped; our
sun is on a spiral arm of the
Milky Way
3. Irregular - many different
shapes that aren't like the other
two

90. XIV. Quasar
 Quasi stellar radio source
 Galaxies, very far away, with bright centers
 Thought to have a super massive black hole at
center
 Most luminous objects known to man

91. XV. Electromagnetic
Spectrum
 The arrangement of electromagnetic
radiation from Radio waves to Gamma
waves

92. Stars Emit:
1. Visible light
2. X-rays
3. Radio waves
4. Infrared waves
5. Ultraviolet waves

93. Venus & Saturn by E-
spectrum
Ultra violet Visible Infrared Radio
Ultra violet Visible Infrared Radio

94. X-ray & Ultra Violet Image of
Sun

95. Visible, Infrared & Radio Images
of Sun

96. A. Electromagnetic waves:
 Differ in wavelength & frequency
 All electromagnetic waves travel at the
speed of light; 300,000 km/sec

97. Parts of a Wave

98.  a has a longer wavelength (distance from
one crest to another) but lower frequency
( # of waves that pass by a point in a
second)

99.  b has a shorter wavelength but a higher
frequency

100. B.
Spectroscope
 Instrument that separates light
into its colors.
 Contains:
 Prism at one end
 Slit at opposite end which
lines up with the light source

101. C. 3 Types of Spectra
1. Continuous Spectrum
2. Brightline Spectrum
3. Darkline Spectrum

102. How Spectra are Produced

103. 1. Continuous Spectrum
 Produced by a glowing solid
 Example a Tungsten white light bulb, &
white sunlight.

104. Continuous Spectrum Cont’
 Continuous set of emission lines forming
an unbroken band of colors from red to
violet.
 Shows the source is sending out light of
all visible wavelengths.

105. Visible Spectrum
 ROY G BIV
 All the colors of
the rainbow
 A continuous
spectrum
red orange yellow green blue indigo violet

106. 2. Dark-Line Spectrum /
Absorption Spectrum
 Produced when a cooler gas lies
between the observer and an object
emitting a continuous spectrum
 Example:
1. The atmosphere of planets
2.Outer layers of a star

107. Absorption Spectrum Cont’
 The cooler gas absorbs specific
wavelengths of radiation passing through
it.
 This spectrum appears as a continuous
spectrum of all colors with a number of
gaps or dark lines throughout it.

108. 3. Bright-Line Spectrum /
Emission Spectrum
 Produced by a glowing gas which radiates
energy at specific wavelengths
characteristic of the element or elements
composing the gas
 Example Neon signs, black lights, LED’s

109. Emission Spectrum Cont’
 This spectrum consists of a number of
bright lines against a dark background.
 Each elements has its own distinctive
spectra much like a fingerprint
http://jersey.uoregon.edu/vlab/elements/Elements.html

110. XVI. The Doppler Effect
 as sound approaches the wavelength is
compressed so the pitch is higher
 as sound leaves the wavelength is
stretched out so the pitch is lower
 The same thing happens with light

111. Doppler Effect
http://hea-www.harvard.edu/~efortin/thesis/html/Doppler.shtml

112. Red Shift
 If a star is moving away from Earth there
is a red shift, of its line spectra; if the star
is moving toward the Earth there is a blue
shift of its line spectra

113. Red Shift
 Red shift is evidence the universe is
expanding.