UNIT 3
Chapter 7: The Night Sky
Chapter 8: Exploring Our Stellar Neighbourhood
Chapter 9:The Mysterious Universe
The Study of the
Universe
CHAPTER 9 The Mysterious Universe
In this chapter, you will:
• identify the three main types of galaxies
• describe the shape and size of the Milky Way galaxy
• describe evidence that supports the big bang theory and an evolution
model of the universe
• identify spinoff technologies that have resulted from studying space
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Galaxies are huge, rotating collections of stars, planets, gas, and dust.
They are held together by gravity.
Matter in Motion
How can you model galaxy rotation?
(Page 359)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
A galaxy is a huge, rotating collection of stars, planets, gas, and dust
held together by gravity.
9.1 Galaxies
In 1780, William Herschel discovered that the Milky Way is made up
of stars. Previously, many thought the hazy, white band in the night
sky was made of clouds.
(Page 361)
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There are three basic shapes of galaxies: spiral, elliptical, and
irregular.
The Shapes of Galaxies
Spiral galaxies, shown in
images (A) and (B), look like
pinwheels with spiralling
arms when viewed from the
top, and like plates with a
middle bulge when viewed
from the side.
Elliptical galaxies (C) range
from perfect spheres to
stretched out ellipses.
Irregular galaxies (D) make
up all other shapes.
(Page 362)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
William Herschel thought that the Milky Way was a huge disk of
billions of stars, possibly with the Sun at its centre.
Understanding the Milky Way Galaxy
In the early 20th century the American astronomer Harlow Shapely
studied star clusters (collections of star held together by gravity)
within the Milky Way, proving the Sun is nowhere near its centre.
Open clusters are collections of
50 to 1000 stars that appear along
the main band of the Milky Way.
Globular clusters are
collections of 100 000 to a
million stars arranged in a
distinctive spherical shape.
They appear around the
centre of the Milky Way.
(Page 363)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Scientists have mapped the Milky Way with radio waves. They found
that its diameter is 100 000 light-years and its shape is disk-like.
The Diameter and Centre of the Milky Way
Using radio waves as well as infrared radiation, astronomers
confirmed that the centre of the Milky Way is surrounded by a bulge of
stars. Globular clusters form a sphere around its centre.
The Milky Way is a
spiral galaxy of about
200 billion solar
masses.
The Sun is about 28 000
light-years from the
centre of the galaxy.
(Pages 363-4)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Reviewing The Milky Way and Galaxy Formation
Click the “Start” buttons to review the Milky Way and galaxy formation.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
The Local Group is a small group of galaxies that includes the Milky
Way. It has a diameter of about 10 million light-years.
The Local Group
The Milky Way and
Andromeda are the
largest galaxies in the
Local Group. Most of
the other galaxies are
small, elliptical
companions to the
larger galaxies.
(Page 365)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Superclusters are gigantic clusters of 4 to 25 clusters of galaxies that
are hundreds of millions of light-years in size.
Galaxy Superclusters
Astronomers hypothesize
that there may be more
than 125 billion galaxies,
and nearly all of them are
organized into clusters.
Credit: NASA Jet Propulsion Laboratory (NASA-JPL)
(Page 366)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Section 9.1 Review
Concepts to be reviewed:
• How are galaxies classified? What major classifications are
used?
• What type of galaxy is the Milky Way? How large is it? What
group of galaxies does it belong to?
• How are astronomers able to determine the composition, size,
and shape of galaxies?
(Page 367)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Cosmology is the study of the universe, including its origin, how it is
changing, and its future.
9.2 The Universe
Using instruments such as the HST, astronomers can examine galaxies
that must have formed shortly after the universe formed.
The American
astronomer Edwin
Hubble (1889-1953)
photographed and
recorded distant
galaxies and studied
their spectra. The
Hubble Space Telescope
(HST) was named in his
honour.
(Page 368)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
The Doppler effect is the change in frequency of a light source due to
its motion relative to an observer. It is also the change in pitch of a
sound due to the motion of the source related to an observer.
The Doppler Effect
The redshift shown in image C is the effect in which objects moving
away from an observer have their wavelengths lengthened, towards the
red end of the spectrum. With a blueshift, shown in image B,
wavelengths are shortened towards the blue end of the spectrum.
In A the star is not moving; in B
the star is moving towards the
observer or blueshifted; and in
C the star is moving away from
the observer or redshifted.
The Doppler effect can be
observed in spectral star data.
(Page 369)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
In 1929, Edwin Hubble and Milton L. Humason discovered a
relationship between a galaxy’s redshift and its distance from Earth.
The Expanding Universe
Russian-American astronomer George Gamow realized the
significance of this relationship and theorized that the universe is
expanding.
The graph on the left shows
that the speed of a galaxy is
proportional to the galaxy’s
distance from Earth. This
relationship is called the
Hubble law, and the slope
of the line is known as the
Hubble constant.
A megaparsec (MPC) is equal to one million
parsecs (3.26 million light-years) and is the unit of
distance commonly used to measure the distance
between galaxies.
(Pages 370-1)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Space Exploration Spinoffs
Spinoffs are products originally designed for one use that have been
adapted for other everyday uses. The high cost of space exploration
has been offset somewhat by the generation of unexpected and useful
spinoffs. A few examples are:
• protective suits for racing crews, U.S. Navy divers, and firemen
• star mapping technology for use in detecting breast cancer
• eye-controlled switches for use by handicapped people
• thin, lightweight, and shiny insulation materials
• radiation monitors
(Pages 370-1)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
The big bang is the event that
may have triggered the
expansion of the universe.
The Big Bang Theory
There is now convincing evidence that the big bang may have
occurred.
The Big Bang Theory states that the
universe began expanding with
unimaginable violence from a hot and
incredibly dense state to its present state.
Cosmologist believe that at some time in the distant past, the universe
was extremely compact, small, and unimaginably dense. Evidence
from satellites suggest that the universe began expanding about 14
billion years ago.
(Images courtesy of NASA/Goddard Space Flight Center
(Page 372)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Hubble and Humason’s distance–redshift relationship supports the idea
of a big bang. A second piece of information that supports the theory is
the cosmic microwave background (CMB) radiation, which is
radiation left over from the big bang.
Evidence of the Big Bang
The universe was originally filled with gamma rays (radiation with
very short wavelengths). As the universe expanded, the gamma
radiation was stretched into visible light, and then eventually into
microwaves. It is this background energy that we find today.
(Page 372)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
In 1965, two American scientists working for Bell Telephone Labs,
Robert Wilson and Arno Penzias, discovered the background
radiation that Gamow predicted would be left over from the big bang.
The discovery was made while trying to determine the source of radio
static/noise. The scientists won the 1978 Nobel prize in physics for
their efforts.
Uncovering the CMB Radiation Evidence
Bell Labs horn radio
antenna in New Jersey
where the background
radiation was discovered
Credit: NASA
(Page 373)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
The COBE (Cosmic Background Explorer) and WMAP (Wilkinson
Microwave Anisotropy Probe) are two NASA satellites that were
designed to measure background radiation left over from the big bang.
COBE and WMAP
The maps above show the CMB radiation (represented mostly in
green) that the probes detected.
COBE
WMAPCredit: NASA/LAMBDA
Credit: NASA/WMAP Science Team
(Page 373)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Modern telescopes can see enormous distances into the universe,
which means they can see very far back into the past. Seeing stars that
are 10 billion light-years away gives us a view of the universe as it
was 10 billion years ago. The COBE and WMAP images represent the
universe when it was only 380 000 years old (0.002% of its current
age). The timeline below represents the evolution of the universe.
Looking Back in Time (Page 374)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Reviewing The Big Bang
Click the “Start” button to review the evolution of the universe.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
NASA plans to launch the James Webb Space Telescope (JWST) in
2013 to replace the Hubble Space Telescope. With its much larger
mirror, the JWST will be able to see much farther into space, back to
when the first galaxies were formed.
The James Webb Space Telescope
The much larger JWST mirror is only half the mass of the HST mirror.
Credit: NASA
(Page 375)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
CERN
CERN (The European Organization for Nuclear Research),
located in Switzerland, operates the world’s more powerful machine
for studying particles at high energies. The Large Hadron Collider
(LHC) can conduct experiments at energies found in the universe
10-12s after the big bang, revealing secrets of the early universe.
© Copyright CERN
(Page 375)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Section 9.2 Review
Concepts to be reviewed:
• What observations led to the discovery that the universe was
expanding?
• What spinoff products have been developed due to space
exploration?
• What is the most widely accepted theory of the beginning of the
universe? What details describe this theory?
(Page 376)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
The universe still holds many mysteries and secrets. One of these
mysteries is dark matter. Dark matter is the most abundant form of
matter in the universe, but it is invisible to telescopes.
9.3 Unsolved Mysteries
The light blue areas in image (B) represent a computer generation of
where the dark matter might be.
(Page 377)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Using the estimated
mass of the Andromeda
galaxy, astronomers
predicted the speeds of
stars at various
distances from its
centre. They found that
the stars were moving
much faster than
expected.
Dark Matter and the Andromeda Galaxy
The astronomers could explain the speed differences by assuming that
the galaxy contained 90% more mass than what was visible. Since the
missing mass did not emit any light, it could not be seen. For this
reason the missing mass was given the name dark matter. Dark matter
has yet to be detected, and its true identity remains unknown.
The dark matter in and around Andromeda
is represented by the blue sphere.
(Page 378)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Astronomers believe that the Milky Way is sitting in a huge halo of
dark matter. The mass of the Milky Way has been estimated at 200
billion solar masses. After observing the motion of galaxies within the
local group, astronomers suggested its mass is at least 10 times larger.
Dark Matter and the Milky Way Galaxy
This means that only 10% of the Milky Way is composed of visible
matter. The remaining 90% is, theoretically, dark matter. Astronomers
believe that visible matter makes up only 4% of the universe; dark
matter makes up 23%; and dark energy makes up the rest.
(Page 379)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Dark energy is a form of energy that makes up nearly three-quarters
of the universe. Dark energy has the effect of increasing the expansion
of the universe.
Dark Energy
Astronomers predicted that after the
Big Bang, the expansion of the
universe would be decreasing due to
gravity. Instead, supernovae were
found farther away than was
expected. This meant that the
opposite was actually true: expansion
was accelerating. Something must be
counteracting gravity and
accelerating the expansion. That
“something” was given the name
dark energy.
(Page 380)
The expansion of the
universe began accelerating
about 7 billion years ago.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Section 9.3 Review
Concepts to be reviewed:
• What is dark matter? What observations made scientists
hypothesize its existence?
• What portion of the universe is composed of dark matter?
• What is dark energy? How does it affect the expansion of the
universe?
(Page 381)