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Chapter 1
Astronomy: The Original Science
 Section 1 Vocabulary
 Astronomy
 Year
 Month
 Day
Introduction
 Seasonal cycles of the
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stars, planets, and the
moon to mark the
passage of time
Best times of year to
plant and harvest crops
Observatories
Study of the universe
Led to first calendars
Our Modern Calendar
 Based on the observations
of bodies in our solar
system
 Time required for the
Earth to orbit once around
the sun
 Roughly the amount of
time required for the moon
to orbit around the Earth
 The time required for the
Earth to rotate once on its
axis
Who’s Who of Early Astronomy
 Helped people
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understand their place in
the universe
Oral histories
Discovered with their
eyes and minds
Stars edge of the
universe
Ptolemy and Copernicus
Ptolemy: An Earth-Centered
Universe
 140 CE –book that
combined all the ancient
knowledge of astronomy
that he could find
 Ptolemaic theory
 Earth was at the center of
the universe and the
other planets revolved
around Earth
(geocentric)
Copernicus: A Sun Centered
Universe
 1543-New theory that
will eventually
revolutionize astronomy
 Sun is at the center of
the universe
(heliocentric)
 Did not replace
Plotemaic theory
immediately
 Coperinican Revolution
Tycho Brahe: A Wealth of Data
 Late-1500’s-several large
tools to make the most
detailed astronomical
observations
 Different geocentric
model
 Sun and moon revolve
around Earth
 Planets move around
the sun
Johannes Kepler: Laws of Planetary
Motion
 Brahe’s assistant –
continued his work
 Did not agree with his
theory
 1609-all of the planets
revolve around the sun
in elliptical orbits and
the sun is not in the
exact center of the orbits.
 3 laws of planetary
motion
Galileo: Turning a Telescope to the
Sky
 1609-one of the first
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people to use a telescope
to observe objects in
space
Craters and mountains
on the Earth’s moon
Four of Jupiter’s Moons
Sunspots on the Sun
Phases of Venus
Not “Wandering Stars”
but physical bodies
Isaac Newton: The Laws of Gravity
 1687-all objects in the
universe attract each
other through
gravitational force
 Force of gravity depends
on the mass of the
objects and the distance
between them
 Explained why we travel
around the sun
Modern Astronomy
Edwin Hubble: Beyond the Edge of
the Milky Way
 Two Milestones
 Invention of the Telescope
 Description of Gravity
 Before the 1920’s –thought
the Milky Way (our galaxy)
included every object in
space
 1924-proved that other
galaxies existed beyond
our galaxy
 Computers help process
data and control the
movement of telescopes
Telescopes
 Section 2 Vocabulary
 Telescope
 Refracting Telescope
 Reflecting Telescope
 Electromagnetic Spectrum
Introduction
 Standard tool
 Professional
astronomers
 Amateur stargazers
 An instrument that
gathers electromagnetic
radiation from objects in
space and concentrates it
better for observation
Optical Telescopes
 Most common
 Study visible light from
objects in the universe
 Helps to see so much more
in the sky
 Collects visible light and
focuses it to a focal point
for closer observation
 The point where the rays
of light that pass through
the lens or that reflect
from a mirror coverage
Optical Telescopes
 Simplest telescope has two
lens
 1. Objective Lens- collects
light and forms an image
at the back of the
telescopes
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The bigger the lens
The more light can gather
 2. Second lens-located in
the eyepiece of the
telescope
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Magnifies the image
produced by the objective
lens
Refracting Vs. Reflecting
Refracting Telescopes
Reflecting Telescopes
 Telescopes that use lenses to
 Telescope that uses a curved
gather and focus light
 Objective lens that bends
light that passes through it
and focuses the light to be
magnified by an eyepiece
 Two Disadvantages
 Cannot be perfectly focused
 Size is limited due to the
objective lens
mirror to gather and focus light
 Light enters the telescope and
is reflected from a large curved
mirror to a flat mirror
 Flat mirror focuses the image
and reflects the light to be
magnified
 Advantages
 Mirrors can be very large
 Prevents light from entering
the glass
 Focus all colors of light to the
same focal point
Refracting Vs. Reflecting
Refracting Telescopes
Reflecting Telescopes
Very Large Reflecting Telescopes
 Several mirrors work
together to collect light
and focus it in the same
area
 Hawaii
 Twin telescopes
 36 hexagonal mirrors that
work together
 Linking several mirrors-
more light to be collected
and focused in one spot
Optical Telescopes and the
Atmosphere
 Light gathered by
telescopes on the Earth is
affected by the atmosphere
 Atmosphere
 Causes starlight to
shimmer and blur due to
the motion of the air
above the telescopes
 Light pollution from large
cities can make the sky
look bright
 Places for telescopes
 Dry areas
 Mountaintops
Optical Telescopes in Space
 Telescopes in space
 Hubble Space Telescope
 2.4 meters across
 Can detect very faint
objects in space
The Electromagnetic Spectrum
 Visible light
 Light that we can see
 Not the only form of
radiation
 1852-James Clerk Maxwell
proved that visible light is
part of the electromagnetic
spectrum
 Made up of all of the
wavelengths of
electromagnetic radiation
Detecting Electromagnetic
Radiation
 Each color of light is a
different wavelength of
electromagnetic radiation.
 We can see
 Red light-long wavelength
 Blue light-short wavelength
 Rest of electromagnetic
spectrum-radio waves,
microwaves, infrared light,
etc.
 Atmosphere blocks most
invisible radiation
 Can pass through-radio
waves, microwaves, visible
light, etc.
Nonoptical Telescopes
 To study invisible
radiation
 Detect radiation that can
not be seen by the
human eye
 Each type of radiation
reveals different clues
about an object
Radio Telescopes
 Detect Radio waves
 Much larger than optical
telescopes –radio waves
are much longer than
optical wavelengths
 Most can be detected day
and night
 Does not have to be solid
Linking Radio Telescopes
 More detailed images
 Work like on large
telescope
 Very Large Array
 27 radio telescopes
 30km
Nonoptical Telescopes in Space
 Most blocked by the
earth’s atmosphere
 Put a lot of them in
space
 Chandra X-Ray
Observatory
 Detects X-Rays
 Much more sensitive
Mapping the Stars
 Section 3 Vocabulary
 Constellation
 Zenith
 Altitude
 Horizon
 Light-year
Patterns in the Sky
 Ancient cultures
connected stars in patterns
 Named sections of the sky
based on the patterns
 Sections of the sky that
contain recognizable star
patterns
 Help navigate and keep
track of time
 Different civilizationdifferent names
 Orion
Constellations Help Organize the
Sky/Seasonal Changes
 A Region in the sky
 Shares a border with its
neighbor
 Like states
 Every star or galaxy is
located within 1 of 88
constellations
 As the Earth revolves
around the sun, the
apparent locations of the
constellations change from
season to season.
Finding Star in the Sky
 Astrolabe-can be used to
describe the location of a
star or planet-Used on
relation to you
 Need to know three points
of reference
 Zenith
 Altitude
 Horizon
 If you want to describe a
star’s location in a relation
to the Earth, you need to
use the celestial sphere
The Path of Stars Across the Sky
 Most stars and planets rise
and set throughout the
night-apparent motion is
caused by the Earth’s
rotation
 Poles- the stars are
circumpolar
 Stars that can be seen at
all times of the year and all
times of night
 They never set.
 Different areas of the
universe are visible
The Size and Scale of the Universe
 Looking out a car window at
trees
 Objects that are very far away
do not appear to move at all
 Same for stars and planets
 1500’s-Nicolaus Coperinicus
noted that the planets
appeared to move relative to
each other but the stars did
not
 Thought that the stars must
be much farther away than
the planets
Measuring Distance in Space
 Copernicus was correct.
 Light-Year-Unit of
length equal to the
distance that light travels
in 1 year
 9.46 trillion kilometers
 Farthest objects we can
observe are more than 10
billion light-years away
The Doppler Effect
 Car Horn
 Doppler Effect-also occurs
with light
 If a light source is moving
quickly away from an
observer, the light emitted
looks redder than it normally
does
 Redshift
 If a star is moving quickly
toward an observer its light
appears bluer than it
normally does
 Blushift
An Expanding Universe
 Hubble-analyzed the light
from galaxies and stars to
study the general direction
that objects in the universe
are moving
 Light from all galaxies
except our close neighbors
is affected by redshift
 Rapidly moving away from
each other
 All galaxies except our
close neighbors are moving
apart, the universe must be
expanding