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

UNIT 3

Chapter 7: The Night Sky

Chapter 8: Exploring Our Stellar Neighbourhood

Chapter 9:The Mysterious Universe

The Study of the

Universe

CHAPTER 8Exploring Our Stellar

Neighbourhood

In this chapter, you will:

• discuss a range of technologies used to study objects in the sky

• assess some of the costs, hazards, and benefits of space exploration

• describe the Sun’s composition and energy source and explain how

the Sun’s energy warms Earth and supports life on the planet

• compare star temperatures and colours and understand how stars

evolve

Copyright © 2010 McGraw-Hill Ryerson Ltd.


What factors must be considered when planning a trip to the Moon?

Preparing for a Trip to The Moon (15)


People explore to better understand the world around them and to find

new resources and places to live.

8.1 Exploring Space

It is difficult, costly, and

dangerous to send humans into

space. In addition to manned

space exploration, humans can

explore space from Earth using

telescopes and other

instruments, as well as through

the use of unmanned space

satellites, probes, orbiters, and

landers.

(Page 317)


The telescopes that astronomers use to study space all detect

electromagnetic radiation. Electromagnetic radiation is radiation

consisting of electromagnetic waves that travel at the speed of light.

The electromagnetic spectrum is shown below.

Exploring Space With Telescopes (Page 318)


Optical telescopes detect visible light. Refracting telescopes use a

lens to collect the light from an object. Reflecting telescopes use

mirrors to collect the light. They both require darkness and clear skies.

Optical Telescopes (Page 319)


Non-optical telescopes detect

non-visible radiation. Radio

telescopes detect radio waves.

Since radio waves can travel

through clouds and do not

require night-time conditions to

be detected, they can be studied

in both day and night and even

in cloudy weather.

Non-optical Telescopes (Page 319)


Much of the radiation that reaches

Earth from space is absorbed by

the atmosphere and never reaches

Earth’s surface. Placing telescopes

above the atmosphere allows us to

explore space in more detail, but

there are advantages and

disadvantages to the technology.

Telescopes in Space (Page 320)


MOST (Microvariability

and Oscillation of STars) is

Canada’s first space

telescope. MOST studies

stars that are similar to our

Sun, one star at a time. A

comparison between MOST

and the Hubble Space

Telescope (HST) is shown

to the right.

MOST: Canada’s “Humble” Space Telescope (Page 321)


Different telescopes

reveal different

information about an

object, depending on the

wavelength of radiation

that is measured.

On the left are four

images of Saturn, each

from a telescope that

detects a different

wavelength. The

wavelengths reveal

different features of

Saturn’s atmosphere.

Studying Objects in Different Wavelengths (Page 322)


Orbiters are

observatories that orbit

other planets. Orbiters use

digital cameras to provide

high-resolution images

not obtainable from Earth.

Planetary Orbiters and Landers

Landers are spacecraft

designed to land on

planets. Landers cannot

move around so they

sample only a fraction

of the environment

being explored.

Phoenix Lander

Messenger

Orbiter

Mars

Climate

Orbiter

(Page 323)


Lidar (Light Detection and Ranging) is an instrument that uses a laser

to analyse atmospheric conditions, collecting information on the size,

movement, and composition of clouds and dust particles above.

The Lidar Instrument

The Lidar device on the Mars Phoenix Lander was constructed and

operated by Canadian scientists. The device has provided valuable

information about the Martian atmosphere.

(Page 324)


Satellites are artificial (human-made) objects or vehicles that orbit

Earth, the Moon, or other celestial bodies. Celestial bodies (like the

Moon) that orbit a larger-sized celestial body are natural satellites.

Satellites

Communication satellites play a role in the operation of television,

telephones, and the Internet. GPS satellites aid in navigation, farming,

and search and rescue operations.

(Page 325)


Satellites that orbit less than 700 km above Earth’s surface are called

low-Earth-orbit satellites. These satellites can survey Earth quickly

and cover a lot of surface. This makes these remote sensing satellites

very useful for the sciences of meteorology (weather), climatology

(climate), oceanography (oceans), and hydrology (water).

Remote Sensing Satellites

The ENVISAT images above show

changes in ice cover.

ENVISAT (ENVironmental

SATellite) is a remote-

sensing satellite that Canada

helped fund. ENVISAT

monitors cloud cover, ocean

ice, ocean height, land

surfaces, and major lakes and

rivers.

(Page 325)


Geosynchronous Satellites

Geosynchronous satellites orbit Earth in an

eastward direction at an altitude of 35 800 km above

the equator. At this altitude, the satellites remain

over the same location above the equator, making

them stationary with respect to Earth (geo-

stationary). These satellites are most commonly used

for communication purposes such as television and

satellite radio.

(Page 327)


The international Space Station

The International Space Station (ISS) orbits about 360 km above

Earth, where it serves as a space-based laboratory. The ISS provides

many opportunities for conducting research in a microgravity (or

weightless) environment. The Canadian Space Agency (CSA) has been

involved with the ISS since its beginning.

(Page 327)


Canadian Contributions to the ISS

Canada has contributed

astronauts to the construction

and operation of the ISS.

The Canadian-designed

Canadarm, Canadarm2, and

Dextre robotic fixtures were

and continue to be essential for

the construction, operation,

and maintenance of the ISS.

Astronaut

Hadfield on

Canadarm2

Dextre

Roberta Bondar

Chris Hadfield

Julie Payette

Robert Thirsk

(Page 328)


Reviewing Satellite Orbits

Click the “Start” button to review satellite orbits.

http://www.mytextbook.ca/product/9780070318618/itr/ppt/assets/OS9.PPT.U3.CH8.slide18.SatelliteAnim_REV.swf.html

http://www.mytextbook.ca/product/9780070318618/itr/ppt/assets/OS9.PPT.U3.CH8.slide18.SatelliteAnim_REV.swf.html


The Cost and Ethics of Space Exploration

It takes years of designing and testing the equipment, spacesuits, and

the computer software needed to send people and vehicles into space.

As a result, space exploration is very expensive. In addition, sending

humans into space is extremely risky, and human lives have been lost

on space missions. A variety of issues must be considered.

A person’s ethics

are the set of

moral principles

and values that

guide a person’s

activities, helping

him or her decide

what is right.

(Page 330)


Space Junk

Space agency scientists are researching ways to clean up and reduce

the amount of space junk currently orbiting Earth.

Space junk can cause a great deal of damage to spacecraft and

satellites if they happen to collide with it.

(Pages 330-1)


Section 8.1 Review

Concepts to be reviewed:

• What are the two types of optical telescopes? How do they

function?

• What other types of radiation can be detected by telescopes?

• What are the alternatives to human exploration of space?

• What are the hazards, benefits, and ethical issues related to space

exploration?

• How has Canada contributed to the exploration of space?

(Page 332)


Our Sun, a star, is the most important celestial object for life on Earth.

The solar nebula theory is the current theory used to explain the

formation of the Sun.

8.2 Exploring the Sun

The solar nebula theory describes how stars and planets form from

contracting, spinning disks of gas and dust. Nebulas are vast clouds of

gas and dust that may be the birthplace of stars and planets.

Stars are celestial

bodies made of hot

gases, mainly hydrogen

and some helium.

(Page 333)


How does a solar system form? It

is believed that gravity sets the gas

and dust particles of a nebula in

motion around the core of a young

star or protostar (a condensed, hot

object at the middle of a nebula).

Particles begin to gather in the

centre of the spinning cloud. As

the spinning nebula begins to

contract, tiny grains start to collect

and eventually clump into

planetesimals. If the planetesimals

survive, they may eventually form

planets like those in our solar

system.

How the Solar System Formed

Craters on rocky planets could

have formed during early

formation.

(Page 334)


As nebulas spin, they flatten into a disk-like shape while spinning in

one direction. Astronomers theorize that any planets and other bodies

that form at this stage would form in the flat plane of the disk. The

planets would then orbit in that same direction.

A Flat, Rotating Disk

Astronomers have discovered over 300 planets orbiting stars other

than the Sun. These planets are called extrasolar planets. Several

extrasolar planets (a-d) are shown orbiting the star HR8799.

(Page 335)


When a star-forming nebula collapses and contracts, the gas

compresses and the temperature of the protostar increases. When the

temperature reaches around 10 000 000oC, nuclear fusion begins.

How the Sun Formed

Once the fusion process begins, the protostar starts to consume the

hydrogen fuel. The denser helium builds up in the star’s core, and the

core continues to heat up, increasing the pressure and temperature. The

continuing hydrogen fusion increases the size of the core.

Nuclear fusion is the process of energy

production in which hydrogen nuclei combine

to form helium nuclei.

(Page 336)


The surface layer of the Sun is known as the photosphere. This layer

is several thousand kilometres deep. Dark spots on the photosphere,

called sunspots, are areas of strong magnetic fields. The sunspots look

dark because they are cooler than the surrounding photosphere.

Features of the Sun

Astronomers have observed that

sunspots near the Sun’s poles

take about 35 days to complete

one rotation while sunspots near

the equator take 27 days. This

proves that the Sun rotates but

faster at its equator than at the

poles.

Sunspot activity occurs in 22 year cycles, peaking every 11 years.

(Page 337)


Occasionally solar flares can occur where there are complex groups

of sunspots. Solar flares eject intense streams of charged particles into

space. If one of these streams, called solar wind, hits Earth,

spectacular auroras can be produced by Earth’s magnetic field. These

events, called solar storms, can disrupt telecommunications, damage

electronic equipment on spacecraft, and overload Earth’s electrical

power network.

Solar Flares (Page 338)


The Sun drives most processes on Earth that support our daily

activities. It powers the winds and ocean currents, drives all weather,

and provides the energy for the photosynthesis that provides food at

the base of all food chains and the oxygen we breathe.

The Importance of the Sun

The Sun produces radiation across the entire electromagnetic

spectrum, including the radiation that heats Earth.

(Page 339)


Section 8.2 Review


• How does the solar nebula theory explain the formation of the

solar system?

• What evidence do astronomers have that the solar nebula theory

might be at work elsewhere in the universe?

• What is the Sun’s energy source? How is this energy released?

• What are sunspots and solar flares? How can they affect Earth?

• How does energy that originated from the Sun warm Earth?

(Page 340)


The night sky is filled with stars that shine at different levels of

brightness. The brightness of the stars we observe can be related to the

size of the star or its distance from Earth.

8.3 Exploring Other Stars

The brightness or luminosity of

a star is described as its energy

output per second. The star’s

power is measured in joules per

second (J/s). The absolute

magnitude of a star is the

brightness we would observe if

the star were placed 32.6 light-

years from Earth.Our Sun has an absolute

magnitude of 4.7. By universal

standards, this is quite dim.

(Page 341)


Astronomers use the colour of stars to determine temperature. In order

of increasing temperature, stars can be red, orange, yellow, or blue.

The Colour, Temperature, Composition, and Mass of Stars

A star’s mass can be determined if

it is part of a binary star system.

Binary stars orbit each other. Stars

range from 0.08 to over 100 solar

masses. Our Sun is 1 solar mass.

Spectroscopes (devices that

produce a spectrum from a

narrow beam of light) produce

spectral lines that can be used

to determine the chemical

composition of a star. The

spectral lines produced by the

spectroscope have black lines

that indicate the presence of

specific elements.

(Pages 342-3)


The Hertzsprung-Russell (H-R) diagram is a graph that compares

the properties of stars. The graph compares absolute magnitude/

luminosity on the y-axis to temperature/colour on the x-axis.

The Hertzsprung-Russell Diagram (Page 343)


The main sequence is a narrow band of stars on the H-R diagram that

runs diagonally from the upper left (bright, hot stars) to the lower right

(cool, dim stars). About 90% of all stars, including the Sun, are in the

main sequence. Some main sequence properties are listed below.

The Main Sequence

Astronomers are not sure why all stars do not fall into the main

sequence.

(Page 344)


Stars, in general, do not change very rapidly. Many stars shine for

billions of years with no change. Eventually a star will run out of fuel

and will start undergoing changes as it nears the end of its life.

How Stars Evolve

Low-mass stars (red dwarfs)

have less mass than our Sun.

They slowly burn their fuel for

up to 100 billion years and then

end up as small, dim hot stars

called white dwarfs. When

cooled, they become black

dwarfs.

Intermediate-mass stars, like our Sun, consume their fuel within 10

billion years. They cool, and the outer layers expand the star into a red

giant. The layers disappear and eventually they become white dwarfs.

(5)


High-mass stars are 12 or more times more massive than our Sun.

These stars consume their fuel faster than intermediate-mass stars and

die more quickly and violently. Heavy elements form by fusion, and

the star expands into a supergiant. An iron core forms that eventually

collapses, resulting in a massive explosion of the outer part of the star.

This spectacular explosion is called a supernova.

How Stars Evolve

Supernova

explosions can be

millions of times

brighter than the

original star.

Elements from the explosion are

ejected into the universe, later

becoming part of new stars and

planets.

(Page 345)


A neutron star is a star so dense that only neutrons can exist at the

core. This type of star forms when a star of about 12 to 15 solar

masses shrinks to approximately 20 km in diameter. The pressure is so

great that electrons are squished into protons.

Neutron Stars

A neutron star in the Crab Nebula behaves as a pulsar (a type of

neutron star), sending pulses of radiation into space like a giant

searchlight.

(Page 347)


Stars of over 25 solar masses experience the most spectacular deaths.

The remnant of the supernova explosion is so massive that gravity

overwhelms all other forces, and the remnant is crushed into a black

hole. The black hole is a tiny patch of space that has no volume but

has enormous mass. The gravitational force of a black hole is so strong

that nothing can escape it, not even light.

Black Holes

How do scientists find a black hole? Scientists detect the gravitational

effect it exerts on the space around it.

(Page 348)


Section 8.3 Review


• What does a star’s apparent brightness depend on?

• What is the significance of the Hertzsprung-Russell (H-R)

diagram?

• What determines a star’s position in the H-R diagram?

• What determines the changes a star will go through during its

evolution?

(Page 349)

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