Chapter 15 Stars, Galaxies, and Universe
Table of Contents
Chapter Preview
15.1 Telescopes
15.2 Characteristics of Stars
15.3 Lives of Stars
15.4 Star Systems and Galaxies
15.5 The Expanding Universe
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
1. What is light?
a. electrical energy from the sun
b. matter that travels as waves
c. energy that travels in the form of waves
d. matter that allows us to see things
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
1. What is light?
a. electrical energy from the sun
b. matter that travels as waves
c. energy that travels in the form of waves
d. matter that allows us to see things
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
2. As the result of nuclear fusion, the sun gives off
a. mechanical and electrical energy.
b. chemical energy and sound.
c. electrical energy and light.
d. heat and light.
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
2. As the result of nuclear fusion, the sun gives off
a. mechanical and electrical energy.
b. chemical energy and sound.
c. electrical energy and light.
d. heat and light.
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
3. How many stars are in our solar system?
a. one
b. hundreds
c. thousands
d. millions
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
3. How many stars are in our solar system?
a. one
b. hundreds
c. thousands
d. millions
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
4. The planets and moons in our solar system are visible
because they
a. emit their own light.
b. undergo nuclear fusion.
c. absorb light from the sun.
d. reflect light from the sun.
Chapter 15 Stars, Galaxies, and Universe
Chapter Preview Questions
4. The planets and moons in our solar system are visible
because they
a. emit their own light.
b. undergo nuclear fusion.
c. absorb light from the sun.
d. reflect light from the sun.
Chapter 15 Stars, Galaxies, and Universe
What is the structure and composition of
the universe?
Suppose you shine the beam of a
flashlight against the wall of a
darkened room. You then measure
the size of the circle made by the
beam on the room. What do you
think would happen to the size of
the circle if you moved closer to the
wall? Farther from the wall? Explain
your answer.
Chapter 15 Stars, Galaxies, and Universe
End of Chapter
Preview
Chapter 15 Stars, Galaxies, and Universe
Section 1:
Telescopes
What are the regions of the electromagnetic spectrum?
What are telescopes and how do they work?
Where are most large telescopes located?
Chapter 15 Stars, Galaxies, and Universe
Electromagnetic Radiation
Electromagnetic
Energy that travels
radiation
through space in the
form of waves
All colors that can be
Visible light
seen
(Optical)
Roy G. Biv – colors in
the rainbow, through
a prism
Red, orange, yellow,
green, blue, indigo,
violet.
Chapter 15 Stars, Galaxies, and Universe
Electromagnetic spectrum
Types of radiation
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Chapter 15 Stars, Galaxies, and Universe
Electromagnetic Radiation
The electromagnetic spectrum includes the entire range of
radio waves, infrared radiation, visible light, ultraviolet
radiation, X-rays, and gamma rays.
Chapter 15 Stars, Galaxies, and Universe
Types of Telescopes
A refracting telescope uses convex lenses to focus light. A
reflecting telescope has a curved mirror in place of an
objective lens.
Chapter 15 Stars, Galaxies, and Universe
Four Views of the Crab Nebula
Different type of telescopes collect electromagnetic radiation
at different wavelengths. Astronomers are able to learn a
great deal about the Crab Nebula by examining these
different images. The images are shown at different scales.
Chapter 15 Stars, Galaxies, and Universe
Types of Telescopes
Type of Radiation
Radio waves
Infrared
Microwave
X-Ray
Visible
Name and location of What has been
telescope
found?
,
Chapter 15 Stars, Galaxies, and Universe
Ultraviolet
Gamma
GALEX, space
Chapter 15 Stars, Galaxies, and Universe
Links on Telescopes
Click the SciLinks button for links on telescopes.
Chapter 15 Stars, Galaxies, and Universe
Telescopes
Click the Video button to watch a movie about telescopes.
Chapter 15 Stars, Galaxies, and Universe
The Hubble Space Telescope
Click the Video button to watch a movie about
the Hubble Space Telescope.
Chapter 15 Stars, Galaxies, and Universe
End of Section:
Telescopes
Chapter 15 Stars, Galaxies, and Universe
Section 2:
Characteristics
of Stars
How are stars classified?
How do astronomers measure distances to the stars?
What is an H-R diagram and how do astronomers use it?
Chapter 15 Stars, Galaxies, and Universe
Constellation
Stars
Classifying Stars
Imaginary pattern of stars
Made up mostly of H (hydrogen)
Produce energy through nuclear
fusion
Color shows temperature
red – cool stars (3200°C)
yellow – hotter stars
(5500°C)
blue – hottest stars
(20,000°C)
Chapter 15 Stars, Galaxies, and Universe
Chapter 15 Stars, Galaxies, and Universe
Size of Stars
Giant or
supergiant
Medium size
Small size
•Very large stars
•Our sun’s size
•White dwarf – size of
Earth
•Neutron stars – 20 km
diameter.
Chapter 15 Stars, Galaxies, and Universe
Star Size
Stars vary greatly in size. Giant stars are typically 10 to 100
times larger than the sun and more than 1,000 times the size
of a white dwarf.
Chapter 15 Stars, Galaxies, and Universe
Chemical Composition
Spectrograph
•73% hydrogen (H)
•25% helium (He)
•2% other elements
•Breaks light into
different colors
•Can determine gases in
stars.
Chapter 15 Stars, Galaxies, and Universe
Star Spectrums
Astronomers can use line spectrums to identify the chemical
elements in a star. Each element produces a characteristic
pattern of spectral lines.
Chapter 15 Stars, Galaxies, and Universe
Brightness of Stars
Apparent
Brightness
•Amount of light given off
•Depends on size and
temperature
•Betelgeuse – cool and
large, shines brightly
•Rigel – hot, brighter than
Betelgeuse though smaller
•Brightness as seen from
Earth
•Comparative.
Chapter 15 Stars, Galaxies, and Universe
Brightness of Stars
Absolute
Brightness
•No matter where you
measure the brightness,
it has the same
measurement
•Can compare brightness
of all stars to each
other.
Chapter 15 Stars, Galaxies, and Universe
Measuring Distances to Stars
Astronomical
Unit
Light year
•1 A.U. is the distance
between Earth and the sun
•1.44 X 108 kilometers (km).
•Measure distances between
stars
•Distance light travels in one
year
•9.5 X 1012 kilometers (km).
Chapter 15 Stars, Galaxies, and Universe
The Hertzsprung-Russell Diagram
Astronomers use H-R diagrams to classify stars and to
understand how stars change over time.
Compare 2
stars –
color,
brightness,
temp.
Chapter 15 Stars, Galaxies, and Universe
Chapter 15 Stars, Galaxies, and Universe
H-R Diagram
On the H-R diagram:
•Bottom X axis shows temperature, hottest
on left, coolest on right
•Top X axis shows color of stars, blue on left,
red on right
•Y axis shows brightness increasing
Chapter 15 Stars, Galaxies, and Universe
Summary of Section
Use the following as a guide to write a
summary of this section:
Stars are classified by ___________,
_________, _______, ________,
__________. Some stars appear brighter
than others because ___________. Light
years are used to measure distances
between stars because ___________.
The H-R diagram is used to _________.
Chapter 15 Stars, Galaxies, and Universe
More on Types of Stars
Click the PHSchool.com button for an activity
about types of stars.
Chapter 15 Stars, Galaxies, and Universe
End of Section:
Characteristics
of Stars
Chapter 15 Stars, Galaxies, and Universe
Section 3:
Lives of Stars
How does a star form?
What determines how long a star will exist?
What happens to a star when it runs out of fuel?
Chapter 15 Stars, Galaxies, and Universe
Chapter 15 Stars, Galaxies, and Universe
Chapter 15 Stars, Galaxies, and Universe
A Star Is Born
•Nebula – large cloud of gas & dust, large volume
•Gravity pulls gas & dust together
•Forms protostar (no nuclear fusion)
•When gas & dust are very dense & hot, nuclear
fusion starts, a star is born
•Stars with more mass use up fuel faster than
smaller stars
•Small stars – 200 billion years
•Medium stars – 10 billion years (our sun)
•Large stars – 10 million years
Chapter 15 Stars, Galaxies, and Universe
Chapter 15 Stars, Galaxies, and Universe
The Lives of Stars
A star’s life history depends on
its mass. After a star runs out of
fuel, it becomes a white dwarf, a
neutron star, or a black hole.
Chapter 15 Stars, Galaxies, and Universe
The Lives of Stars
A star’s life history depends on its mass. After a star runs out of
fuel, it becomes a white dwarf, a neutron star, or a black hole.
Chapter 15 Stars, Galaxies, and Universe
Deaths of Stars
•Hydrogen fuses to become helium and releases a
lot of energy
•When star uses up hydrogen helium can start
fusing and creating new elements
•Helium fuses in core to become carbon, oxygen
•Massive stars produce heavier elements like iron
•Stars without fuel become white dwarf, neutron
star or black hole
•Low mass star
red giant
planetary
nebula
white dwarf
black dwarf
Chapter 15 Stars, Galaxies, and Universe
Deaths of Stars
•Supernova – explosion of supergiant
•Explosion creates heavy elements, lead, gold
•Explosion creates new stars with material from old
star (recycling!)
•Neutron star – remains of supergiant
•Smaller, denser than white dwarfs
•Pulsar – spinning neutron star
•Gives off pulses of radiation in the form of radio
waves
•Black hole – gravity so strong nothing can escape
•Cannot be detected directly
Chapter 15 Stars, Galaxies, and Universe
The Lives of Stars Activity
Click the Active Art button to open a browser window and
access Active Art about the lives of stars.
Chapter 15 Stars, Galaxies, and Universe
Pulsar
Pulsars are spinning neutron stars that emit steady beams of
radiation.
Chapter 15 Stars, Galaxies, and Universe
Black Holes
The remains of the
most massive stars
collapse into black
holes. Here, a black
hole is shown pulling
matter from a
companion star.
Gas near a black hole pulled inward, x-rays observed, gravitational
effect on nearby stars
Chapter 15 Stars, Galaxies, and Universe
End of Section:
Lives of Stars
Chapter 15 Stars, Galaxies, and Universe
Section 4:
Star Systems
and Galaxies
What is a star system?
What are the major types of galaxies?
How do astronomers describe the scale of the universe?
Chapter 15 Stars, Galaxies, and Universe
Star Systems and Clusters
•Our galaxy = Milky Way
•Star systems – two or more stars together
•Binary stars – two stars or double stars
•One star brighter, more massive
•Dimmer star’s gravity causes “wobble”
•Eclipsing binary – one star blocks light from
another star
•Triple stars – 3 stars together
•Found at least 500 other planets that
revolve around stars- called exoplanets.
•Found by “wobble” of star.
Chapter 15 Stars, Galaxies, and Universe
Star Clusters
•Large groupings of stars
•Formed from same nebula at about same time
•Open clusters – disorganized appearance, a few
thousand stars
•Globular clusters – large groupings of older
stars, more than a million stars.
Chapter 15 Stars, Galaxies, and Universe
Galaxies
•Huge group of single stars, star systems, star
clusters, dust and gas
•Many have black holes in center
•Billions of stars in galaxy
•Billions of galaxies in universe
•Quasar – distant, very bright young galaxy with
black hole in center.
Chapter 15 Stars, Galaxies, and Universe
Types of Galaxies
Astronomers classify most galaxies into three main
categories: spiral, elliptical, and irregular.
Chapter 15 Stars, Galaxies, and Universe
Types of Galaxies
•Spiral – bulge in middle, arms spiral outward
•Spiral arms contain new stars, gas, dust
•New stars formed in spiral arms
•Elliptical – round or oval shape, billions of stars,
little gas or dust, therefore old stars
•Irregular – smaller than other galaxies
•Young stars, lots of gas and dust
•Located close to larger galaxies.
Chapter 15 Stars, Galaxies, and Universe
Structure of the Milky Way
Our solar system is located
in a spiral galaxy called the
Milky Way. From the side,
the Milky Way appears to be
a narrow disk with a bulge in
the middle. The galaxy’s
spiral structure is visible
only from above or below.
Center is 25,000 light years
away from Earth
Chapter 15 Stars, Galaxies, and Universe
Scale of the Universe
Universe
Scientific Notation
•All of space and
everything in it
•Objects are very large
and very far away
•Uses powers of ten to
write very large or very
small numbers
•One light year =
9,500,000,000,000,000
meters. Written as 9.5
X 1015m, 9.5X1012 km.
Chapter 15 Stars, Galaxies, and Universe
Scientific Notation
The bright star Deneb is about 3,230 light-years from Earth.
To express this number in scientific notation, first insert a
decimal point in the original number so that you have a
number between one and ten. In this case, the number
is 3.23.
To determine the power of 10, count the number of places
that the decimal point moved. Here the decimal point moved
three places.
3,230 light-years = 3.23 x 103 light-years.
Chapter 15 Stars, Galaxies, and Universe
Links on Galaxies
Click the SciLinks button for links on galaxies.
Chapter 15 Stars, Galaxies, and Universe
ALL CLASSES: Draw a triple Venn Diagram of
the 3 types of galaxies.
Answer questions 1a,b,c, 2a,b,c, 3a,b,c, and 4 on
P. 621.
End of Section:
Star Systems
and Galaxies
Chapter 15 Stars, Galaxies, and Universe
Section 5:
The Expanding
Universe
What is the big bang theory?
How did the solar system form?
What do astronomers predict about
the future of the universe?
Chapter 15 Stars, Galaxies, and Universe
Retreating Galaxies
All of the distant galaxies astronomers have observed are
moving rapidly away from our galaxy and from each other.
Chapter 15 Stars, Galaxies, and Universe
Speeding Galaxies
Use the graph to answer the
questions about moving clusters
of galaxies.
Chapter 15 Stars, Galaxies, and Universe
Speeding Galaxies
Reading Graphs:
How far away is the Bootes
cluster? How fast is it
moving?
About 2.5 billion light-years;
about 39,000 km/sec
Chapter 15 Stars, Galaxies, and Universe
Speeding Galaxies
Reading Graphs:
Which galaxy is moving away
the fastest? Which galaxy is
closest to Earth?
Hydra; Virgo
Chapter 15 Stars, Galaxies, and Universe
Speeding Galaxies
Drawing Conclusions:
How are the distance and
speed of a galaxy related?
The greater the distance from
Earth, the greater the speed
of the galaxy.
Chapter 15 Stars, Galaxies, and Universe
Speeding Galaxies
Predicting:
Predict the speed of a galaxy
that is 5 billion light-years
from Earth.
Its speed would be about
80,000 km/s.
Chapter 15 Stars, Galaxies, and Universe
Moving Galaxies
The galaxies in the universe are like the raisins in rising
bread dough.
Chapter 15 Stars, Galaxies, and Universe
Formation of the Solar System
The solar system formed from a collapsing cloud
of gas and dust.
Chapter 15 Stars, Galaxies, and Universe
Links on the Expanding Universe
Click the SciLinks button for links on the expanding universe.
Chapter 15 Stars, Galaxies, and Universe
End of Section:
The Expanding
Universe
Chapter 15 Stars, Galaxies, and Universe
QuickTake Quiz
Click to start quiz.