the study of the universe - ms. ho-lau's classroom -...

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.


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?

(59)


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)


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)


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)


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)


Reviewing The Milky Way and Galaxy Formation

Click the “Start” buttons to review the Milky Way and galaxy formation.

http://www.mytextbook.ca/product/9780070318618/itr/ppt/assets/OS9.PPT.U3.CH9.slide8.MilkyWay.disc.flv.html

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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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


Reviewing The Big Bang

Click the “Start” button to review the evolution of the universe.

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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)


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)


Section 9.2 Review


• 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)


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)


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)


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)


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.


Section 9.3 Review


• 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)

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