Tools of Astronomy
Objectives
• Describe electromagnetic radiation.
• Explain how telescopes work.
• Describe space exploration.
Vocabulary
– refracting telescope
– reflecting telescope
– interferometry
– spinoff
Tools of Astronomy
Tools of Astronomy
• The light that comes to Earth from distant
objects is the best tool that astronomers can use
to learn about the universe.
• In most cases, there is no other way to study the
cosmos except to analyze the light that we
receive from it.
Tools of Astronomy
Radiation
• Electromagnetic radiation consists of waves of
electrical and magnetic disturbances.
• It includes visible light, infrared and ultraviolet
radiation, radio waves, microwaves, X rays, and
gamma rays.
Tools of Astronomy
Radiation
• Electromagnetic radiation travels at the same
speed and is classified by:
– Wavelengths—the distance between peaks on a wave.
– Frequency—the number of waves or oscillations
occurring per second.
Tools of Astronomy
Telescopes
• When exploring space, telescopes have
many benefits:
– Detectors can be attached to a telescope to observe all
wavelengths, not just visible light.
– A telescope brings much more light to a focus than the
human eye can, allowing the observation of faint objects.
– Specialized equipment, such as a photometer which
measures the intensity of visible light, can be used with
a telescope.
– With the aid of imaging devices, telescopes can be used
to make time exposures to detect objects that are too
faint for the human eye to see.
Tools of Astronomy
Telescopes
Refracting and Reflecting Telescopes
– Two different types of telescopes are used to focus
visible light.
• Refracting telescopes, or refractors, are telescopes
that use lenses to bring visible light to a focus.
• Reflecting telescopes, or reflectors, are telescopes
that bring visible light to a focus with mirrors.
– Reflectors make up the majority of telescopes that are
in use today.
– Most major observatories are located in remote, high
elevation locations in order to minimize light and
atmospheric interference.
Tools of Astronomy
Telescopes
Refracting and Reflecting Telescopes
Tools of Astronomy
Telescopes
Telescopes at Other Wavelengths
– For all telescopes, the goal is to bring as much radiation
as possible to a focus.
– Interferometry is the process of linking separate
telescopes together so that they act as one telescope.
– This process has been used with radio telescopes for a
number of years and is now being applied to other
telescopes as well.
– The detail in the images that they produce improves as
the distance between the telescopes increases.
Tools of Astronomy
Satellites, Probes, and
Space-Based Astronomy
• Instruments often must be sent into space to
collect information because:
– Earth’s atmosphere blocks infrared radiation, ultraviolet
radiation, X rays, and gamma rays.
– When Earth’s atmosphere does allow certain
wavelengths to pass through, the images are blurred.
– It is the only way to make close-up observations
and even obtain samples from nearby objects in the
solar system.
Tools of Astronomy
Satellites, Probes, and
Space-Based Astronomy
• The Hubble Space Telescope (HST) makes
observations in visible-light, infrared, and
ultraviolet wavelengths.
• Other space-based telescopes, such as the
Far Ultraviolet Spectroscopic Explorer, the
Chandra X-Ray Observatory, and the Spitzer
Space Telescope, observe other wavelengths
that are blocked by Earth’s atmosphere.
Tools of Astronomy
Satellites, Probes, and
Space-Based Astronomy
Spacecraft
– Space-based exploration can be achieved by sending
spacecraft directly to the bodies being observed.
– Robotic probes make close-up observations and
sometimes land to collect information directly.
– More recently, the twin robots Spirit and Opportunity
conducted scientific experiments on Mars in 2004.
Tools of Astronomy
Satellites, Probes, and
Space-Based Astronomy
Human Spaceflight
– Exploring the short term effects of space has been
accomplished with the space shuttle program, which
began in 1981.
– Since habitation and research
began in 2000, a multi-country
space station called the
International Space Station
has been used to study the
long-term effects of life
in space.
Tools of Astronomy
Satellites, Probes, and
Space-Based Astronomy
Spinoffs
– Spinoffs are technologies that were originally
developed for use in space programs that have been
passed on to commercial industries for common use.
– More than 1400 different NASA technologies have been
incorporated into products ranging from artificial hearts
to cordless tools.
Tools of Astronomy
Section Assessment
1. What is the difference between a reflecting and
a refracting telescope?
A reflecting telescope brings visible light to a
focus using lenses, while a refracting telescope
uses mirrors.
Tools of Astronomy
Section Assessment
2. What are the categories of electromagnetic
radiation?
Electromagnetic radiation includes visible light,
infrared and ultraviolet radiation, radio waves,
microwaves, X rays, and gamma rays.
Tools of Astronomy
Section Assessment
3. Identify whether the following statements are
true or false.
______
false Electromagnetic radiation travels at different
speeds that are determined by wavelength.
______
true When applying interferometry, the detail of the
images produced improves as the distance
between telescopes increases.
______
false The Hubble Space Telescope is able to
observe X rays.
______
true More than 1400 spinoffs using NASA
technologies exist.
The Moon
Objectives
• Describe the development of exploration of the Moon.
• Identify features on the Moon.
• Explain the theories about how the Moon formed.
Vocabulary
– albedo
– ejecta
– highland
– ray
– mare (plural, maria)
– rille
– impact crater
– regolith
The Moon
Reaching for the Moon
• Plans for a crewed lunar expedition began in
the late 1950s.
– In 1957 the Soviet Union launched the first satellite,
Sputnik I.
– In 1961, Soviet cosmonaut Yuri A. Gagarin became the
first human in space.
– On May 5, 1961, Alan B. Shepard Jr. became the first
American in space as part of Project Mercury followed
by the two-person crews of Project Gemini.
– On July 20, 1969, the Apollo program landed Neil
Armstrong and Buzz Aldrin on the Moon, during
Apollo 11.
The Moon
Reaching for the Moon
Lunar Properties
– Earth’s moon is one of the largest moons in the solar
system, especially compared to the size of the planet
it orbits.
– The Moon is relatively farther from Earth than most
moons are from the planets they orbit.
– Earth’s moon is a solid, rocky body, in contrast to the
icy composition of the moons of the outer planets.
– Earth’s moon is the only large moon among the
inner planets.
The Moon
Reaching for the Moon
Lunar Properties
The Moon
Reaching for the Moon
The Lunar Surface
– The albedo of the Moon, the amount of sunlight that its
surface reflects, is only about 0.07 (7 percent)
contrasted with Earth’s average of 0.31 (31 percent).
– Because the Moon has no atmosphere, surface
temperatures can range from 400 K (127°C) in sunlight
to 100 K (–173°C) where it is dark.
– There is no erosion on the Moon—except for surface
creep and wear caused by recent impacts—because it
has no atmosphere or flowing water.
– Craters on the Moon are preserved until one impact
covers another.
The Moon
Reaching for the Moon
The Lunar Surface
– The surface of the Moon consists of several features:
• The Highlands are lunar
regions that are light in color,
mountainous, and heavily
covered with craters.
• The Maria (singular, mare) are
lunar regions that are dark,
smooth plains, which on average
are 3 km lower in elevation than
the highlands.
The Moon
Reaching for the Moon
The Lunar Surface
– The surface of the Moon consists of several features:
• Impact craters were formed when objects from
space crashed into the lunar surface.
• Ejecta is material blasted out during impacts that fell
back to the surface.
• Rays are long trails of ejecta that radiate outward
from some craters.
• Rilles are meandering, valleylike structures that are
found in the Maria.
The Moon
Reaching for the Moon
Composition
– The Moon is made up of minerals similar to those of
Earth—mostly silicates.
– The highlands are predominately lunar breccias, which
are rocks formed by the fusing together of smaller
pieces of rock during impacts.
– The maria are predominately basalts that contain
no water.
The Moon
History of the Moon
• Radiometric dating of lunar rocks from the
highlands indicates an age between 3.8 and
4.6 billion years.
• Regolith is a layer of loose, ground-up rock on
the surface of the Moon that formed as a result
of the heavy bombardment during its first 800
million years.
• The maria which are between 3.1 and 3.8 billion
years old formed when lava welled up from the
Moon’s interior and filled in the large impact
basins.
The Moon
History of the Moon
Tectonics on the Moon?
– The Moon, like Earth, has a layered structure, which
consists of the crust, the upper mantle, the lower mantle,
and the core.
– Although the Moon experiences moderate moonquakes
approximately once a year, scientists theorize that the
Moon is not tectonically active.
– That the Moon has no active volcanoes and no
significant magnetic field supports this conclusion.
The Moon
History of the Moon
Tectonics on the Moon?
The Moon
History of the Moon
Formation Theories
– The capture theory proposes that as the solar system
was forming, a large object ventured too near to the
forming Earth, became trapped in its gravitational pull,
and formed into what is now the Moon.
– The simultaneous formation theory states that the Moon
and Earth formed at the same time and in the same
general area, and thus the materials from which they
formed were essentially the same.
The Moon
History of the Moon
Formation Theories
– The impact theory is the most commonly accepted
theory of how the Moon formed.
– This theory proposes that the Moon formed as the
result of a gigantic collision between Earth and a
Mars-sized object about 4.5 billion years ago, when
the solar system was forming.
The Moon
History of the Moon
Formation Theories
The Moon
Section Assessment
1. Match the following terms with their definitions.
___
C maria
___
B albedo
___
D rille
___
A regolith
A. a layer of loose, ground-up
rock on the surface of the
Moon
B. the amount of light a surface
reflects
C. dark, smooth plains, which
are on average 3 km lower
than lunar highlands
D. meandering, valleylike
structures on the Moon
The Moon
Section Assessment
2. Briefly explain the impact theory.
The impact theory suggests that a Mars-sized
body collided with Earth about 4.5 billion years
ago. The impact threw material from the body
and Earth into space where it eventually merged
together to form the Moon.
The Moon
Section Assessment
3. Identify whether the following statements are
true or false.
______
false The United States was the first country to
launch a human into space.
______
false There is only one other large moon among the
inner planets.
______
true On the Moon, craters are preserved until one
impact covers another.
______
true Less than 10 percent of the light striking the
Moon’s surface is reflected back into space.
The Sun-Earth-Moon System
Objectives
• Identify the relative positions and motions of Earth, the
Sun, and the Moon.
• Describe the phases of the Moon.
• Explain eclipses of the Sun and Moon.
Vocabulary
– ecliptic
– synchronous rotation
– summer solstice
– solar eclipse
– winter solstice
– perigee
– autumnal equinox
– apogee
– vernal equinox
– lunar eclipse
The Sun-Earth-Moon System
The Sun-Earth-Moon System
• The relationships between the Sun, Moon, and
Earth are important to us in many ways.
– The Sun provides light and warmth, and it is the
source of most of the energy that fuels our society.
– The Moon raises tides in our oceans and illuminates
our sky with its monthly cycle of phases.
– Every society from ancient times to the present has
based its calendar and its timekeeping system on the
apparent motions of the Sun and Moon.
The Sun-Earth-Moon System
Daily Motions
• The Sun rises in the east and sets in the west,
as do the Moon, planets, and stars as a result of
Earth’s rotation.
• We observe the sky from a planet that rotates
once every day, or 15° per hour.
The Sun-Earth-Moon System
Daily Motions
Earth’s Rotation
– There are two relatively simple ways to demonstrate
that Earth is rotating.
1. A Foucault pendulum, which has a long wire, a heavy
weight, and will swing in a constant direction,
appears from our point of view to shift its orientation.
2. Flowing air and water on Earth are diverted from a
north-south direction to an east-west direction as a
result of Earth’s rotation in what is known as the
Coriolis effect.
The Sun-Earth-Moon System
Daily Motions
Earth’s Rotation
– The length of a day as we observe it is a little longer
than the time it takes Earth to rotate once on its axis.
– Our timekeeping system is based on the solar day,
which is the time period from one sunrise or sunset to
the next.
The Sun-Earth-Moon System
Annual Motions
• The annual changes in length of days and
temperature are the result of Earth’s orbital
motion about the Sun.
• The ecliptic is the plane in which Earth orbits
about the Sun.
The Sun-Earth-Moon System
Annual Motions
The Effects of Earth’s Tilt
– Earth’s axis is tilted relative to the ecliptic at
approximately 23.5°.
– As Earth orbits the Sun, the orientation of Earth’s axis
remains fixed in space.
– At one point, the northern hemisphere of Earth is tilted
toward the Sun, while six months later it is tipped away
from the Sun.
– As a result of the tilt of Earth’s axis and Earth’s motion
around the Sun, the Sun is at a higher altitude in the
sky during summer than in the winter.
The Sun-Earth-Moon System
Annual Motions
The Effects of Earth’s Tilt
Altitude is
measured in
degrees from the
observer’s horizon
to the object. There
are 90 degrees
from the horizon to
the point directly
overhead, called
the zenith of the
observer.
The Sun-Earth-Moon System
Annual Motions
Solstices
– As Earth moves from position 1, through position 2, to
position 3, the altitude of the Sun decreases in the
northern hemisphere.
– Once Earth is at
position 3, the Sun’s
altitude starts to
increase as Earth
moves through
position 4 and
back to position 1.
The Sun-Earth-Moon System
Annual Motions
Solstices
– The summer solstice occurs around June 21 each
year when the Sun is directly overhead at the
Tropic of Cancer, which is at 23.5° N.
– The summer solstice
corresponds to the
Sun’s maximum
altitude in the sky
in the northern
hemisphere.
The Sun-Earth-Moon System
Annual Motions
Solstices
– The winter solstice occurs around December 21 each
year when the Sun is directly overhead at the
Tropic of Capricorn which is at 23.5° S.
– The winter solstice
corresponds to the
Sun’s lowest
altitude in the sky
in the northern
hemisphere.
The Sun-Earth-Moon System
Annual Motions
Solstices
The Sun-Earth-Moon System
Annual Motions
Equinoxes
– When the Sun is directly overhead at the equator, both
hemispheres receive equal amounts of sunlight.
– The autumnal equinox
occurs around
September 21,
halfway between
the summer and
the winter solstices
when the Sun is
directly over the
equator.
The Sun-Earth-Moon System
Annual Motions
Equinoxes
– The vernal equinox occurs around March 21, halfway
between the winter and the summer solstices when the
Sun is directly over the equator.
– For an observer at the
Tropic of Cancer or
Tropic of Capricorn,
the Sun is 23.5° from
the point directly
overhead during the
equinoxes.
The Sun-Earth-Moon System
Annual Motions
Equinoxes
For a person
standing at the x at
23.5º N, the Sun
would appear in
these positions on
the winter solstice,
the vernal equinox,
and the summer
solstice. On the
autumnal equinox,
the Sun would be
at the same
altitude as on the
vernal equinox.
The Sun-Earth-Moon System
Phases of the Moon
• The sequential changes in the appearance of
the Moon are called lunar phases.
– A new moon occurs when the Moon is between Earth
and the Sun and we cannot see the Moon because the
sunlit side is facing away from us.
– As the Moon moves along in its orbit, the amount of
reflected sunlight that we can see increases until we are
able to see the entire sunlit side of the Moon, known as
a full moon.
– Once a full moon is reached, the portion of the sunlit
side that we see begins to decrease as the Moon moves
back toward the new-moon position.
The Sun-Earth-Moon System
Phases of the Moon
The Sun-Earth-Moon System
Phases of the Moon
Synchronous Rotation
– Synchronous rotation is the state at which orbital and
rotational periods are equal.
– As the Moon orbits Earth, the same side faces Earth
at all times because the Moon has a synchronous
rotation, spinning exactly once each time it goes
around Earth.
The Sun-Earth-Moon System
Motions of the Moon
• The length of time it takes for the Moon to go
through a complete cycle of phases is called a
lunar month.
• The length of a lunar month is about 29.5 days,
which is longer than the 27.3 days it takes for
one revolution, or orbit, around Earth.
• The Moon also rises and sets 50 minutes later
each day because the Moon has moved 13° in
its orbit over a 24-hour period, and Earth has to
turn an additional 13° for the Moon to rise.
The Sun-Earth-Moon System
Motions of the Moon
The Sun-Earth-Moon System
Motions of the Moon
Tides
– The Moon’s gravity pulls on Earth along an imaginary
line connecting Earth and the Moon, creating bulges of
ocean water on both the near and far sides of Earth.
– As Earth rotates, these bulges remain aligned with
the Moon.
– When the Sun and Moon are aligned along the same
direction, the result is higher-than-normal tides, called
spring tides.
– When the Moon is at a right angle to the Sun-Earth
line, the result is lower-than-normal tides, called
neap tides.
The Sun-Earth-Moon System
Solar Eclipses
• A solar eclipse occurs when the Moon passes
directly between the Sun and Earth and blocks
our view of the Sun.
– When the Moon perfectly blocks the Sun’s disk, we see
only the dim, outer gaseous layers of the Sun in what is
called a total solar eclipse.
– A partial solar eclipse is seen when the Moon blocks
only a portion of the Sun’s disk.
The Sun-Earth-Moon System
Solar Eclipses
• The shadow that is cast on Earth consists of two
regions.
• A total eclipse occurs in the inner portion called the
umbra, which does not receive direct sunlight.
• A partial eclipse occurs in the outer portion of the
shadow called the penumbra, where some of the
Sun’s light reaches.
The Sun-Earth-Moon System
Solar Eclipses
The Sun-Earth-Moon System
Solar Eclipses
The Effects of Orbits
– The Moon’s orbit is tilted 5° relative to the ecliptic and
usually the Moon passes north or south of the Sun as
seen from Earth, during a new moon.
– A solar eclipse can occur only when the intersection
of the Moon and the ecliptic is in a line with the Sun
and Earth.
The Sun-Earth-Moon System
Solar Eclipses
The Effects of Orbits
– The Moon’s distance from Earth increases and
decreases as the Moon moves in its elliptical orbit
around Earth.
• Perigee is the closest point in the Moon’s orbit
to Earth.
• Apogee is the farthest point in the Moon’s orbit
from Earth.
– When the Moon is near apogee, it appears smaller, and
thus it does not completely block the disk of the Sun,
resulting in an annular eclipse.
The Sun-Earth-Moon System
Lunar Eclipses
• A lunar eclipse occurs when the full Moon
passes through Earth’s shadow.
• A lunar eclipse can happen only at the time of a
full moon, when the Moon is in the opposite
direction from the Sun.
• A total lunar eclipse occurs when the entire Moon
is within Earth’s umbra.
• Solar and lunar eclipses occur in almost equal
numbers, with slightly more lunar eclipses.
The Sun-Earth-Moon System
Lunar Eclipses
The Sun-Earth-Moon System
Section Assessment
1. Match the following terms with their definitions.
___
C ecliptic
___
A summer solstice
___
D winter solstice
___
B apogee
A. occurs when the Sun is
directly overhead at the
Tropic of Cancer
B. the point in the Moon’s
elliptical orbit that is the
farthest from Earth
C. the plane that contains
Earth’s orbit
D. occurs when the Sun is
directly overhead at the
Tropic of Capricorn
The Sun-Earth-Moon System
Section Assessment
2. Number the lunar phases in the correct order,
beginning after the new moon.
___
3 waxing gibbous
___
4 full moon
___
7 waning crescent
___
6 third quarter
___
2 first quarter
___
5 waning gibbous
___
1 waxing crescent
The Sun-Earth-Moon System
Section Assessment
3. Identify whether the following statements are
true or false.
______
false A maximum of five eclipses, solar and lunar
combined, can occur in a year.
______
true The Sun will appear at the same altitude in the
sky during both the autumnal and vernal
equinoxes.
______
false The Earth has a synchronous rotation.
______
true To witness a total solar eclipse, you must be
inside the umbra of the Moon’s shadow.
Chapter Resources Menu
Study Guide
Section 28.1
Section 28.2
Section 28.3
Chapter Assessment
Image Bank
Section 28.1 Study Guide
Section 28.1 Main Ideas
• Visible light, radio waves, infrared and ultraviolet
radiation, X rays, and gamma rays are types of
electromagnetic radiation.
• A telescope collects light over a large area, makes time
exposures, and can use other instruments to analyze light.
• Visible-light telescopes can be made using lenses, as in
refracting telescopes, or mirrors, as in reflecting
telescopes.
• Space is explored by telescopes, satellites, probes,
and humans.
Section 28.2 Study Guide
Section 28.2 Main Ideas
• The first step toward exploration of the Moon was the
launch of the Soviet satellite Sputnik 1. The American
spacecraft Apollo 11 was the first crewed exploration of
the Moon.
• The Moon’s surface has many features that are not present
on Earth because the Moon lacks an atmosphere and
therefore its surface does not undergo erosion.
• Scientists have three theories on how the Moon formed—
simultaneous formation with Earth, a passing object
captured by Earth’s gravity, or as the result of an object
colliding with Earth. The collision theory is the most
widely accepted.
Section 28.3 Study Guide
Section 28.3 Main Ideas
• The entire sky appears to rotate daily because we observe
it from a rotating Earth. Our timekeeping system is based
on the solar day, the length of day as observed from Earth.
• Our view of the Sun’s position changes throughout the
year as Earth moves in its orbit about the Sun. Seasons
occur on Earth because Earth’s axis is tilted.
• The Moon goes through a cycle of phases each lunar
month that correspond to our changing view from Earth of
the sunlit side of the Moon.
Section 28.3 Study Guide
Section 28.3 Main Ideas
• Tides are caused by the gravitational attraction of the
Moon, and to a lesser extent, the gravitational attraction
of the Sun.
• A solar eclipse occurs when the Moon lies directly between
Earth and the Sun. A lunar eclipse occurs when the Moon
passes through Earth’s shadow.
Chapter Assessment
Multiple Choice
1. What is the process of linking separate
telescopes together so that they act as one
telescope called?
a. refraction
c. interferometry
b. reflection
d. binocular
Interferometry has been used with radio telescopes for a
number of years, is now being applied to other
telescopes as well. One of the best known examples of
this technology is the Very Large Array near Socorro,
New Mexico.
Chapter Assessment
Multiple Choice
2. What feature on the Moon was most likely
formed by lava?
a. the highlands
c. rays
b. the maria
d. regolith
The maria were most likely formed when lava welled
up from the Moon’s interior and filled in large impact
basins. The highlands, rays, and regolith were all
formed from impacts.
Chapter Assessment
Multiple Choice
3. How would a zenith of an observer be described
in degrees?
a. 0º
c. 45º
b. 35º
d. 90º
The zenith of an observer is the point directly overhead.
This point is 90º from the horizon.
Chapter Assessment
Multiple Choice
4. During which of the following is the Sun at the
lowest altitude when viewed from 45º N?
a. summer solstice
c. autumnal equinox
b. winter solstice
d. vernal equinox
During the winter solstice, the Sun is directly over the
Tropic of Capricorn (23.5º S), the farthest point south
before direct sunlight begins to move north again.
At 45º N, the Sun’s altitude would only be 21.5º during
the winter solstice.
Chapter Assessment
Multiple Choice
5. Which of the following is the Hubble Space
Telescope unable to observe?
a. visible light
c. X rays
b. infrared
d. ultraviolet
Ultraviolet and infrared wavelengths can be focused by
mirrors in much the same way as visible light. X rays
cannot be focused by normal mirrors, and thus, special
designs must be used. The Chandra X-Ray Observatory
was specifically launched into space to study X rays.
Chapter Assessment
Short Answer
6. What is a synchronous rotation?
A synchronous rotation is a state in which
orbital and rotational periods are equal. For
example, the Moon has a synchronous
rotation, meaning that it spins exactly once
each time it goes around Earth.
Chapter Assessment
Short Answer
7. Why do scientists theorize that the Moon is not
tectonically active?
Scientists theorize that the Moon is not
tectonically active because it has no active
volcanoes or significant magnetic field.
Chapter Assessment
True or False
8. Identify whether the following statements are
true or false.
______
true Earth’s atmosphere blocks infrared radiation.
______
false Human habitation and research aboard the
International Space Station began in 1997.
______
true Sputnik I was Earth’s first artificial satellite.
______
false The Moon’s surface has a very high albedo.
______
false A lunar month is about 35 days.
______
true A partial solar eclipse would be visible to a
person within the penumbra.
Image Bank
Chapter 28 Images
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Image Bank
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