Stars, Galaxies, and the Universe Telescopes Characteristics of Stars Lives of Stars Star Systems and Galaxies The Expanding Universe Table of Contents

Stars, Galaxies, and the Universe

Telescopes

Characteristics of Stars

Lives of Stars

Star Systems and Galaxies

The Expanding Universe

Table of Contents


Electromagnetic Radiation

The electromagnetic spectrum includes the entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

- Telescopes


Types of Telescopes

- Telescopes

A refracting telescope uses convex lenses to focus light. A reflecting telescope has a curved mirror in place of an objective lens.


Four Views of the Crab Nebula

- Telescopes

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.


Building VocabularyCarefully read the definition of each Key Term. Also read the neighboring sentences. Then write a definition of each Key Term in your own words.

- Telescopes

Key Terms: Examples:

telescope A telescope helps to make faraway objects look closer. It is a very valuable tool in astronomy.

electromagnetic radiation

Electromagnetic radiation is a type of energy that travels as waves through space. It includes visible light.

visible light Scientists call the light you can see visible light.

wavelength The distance between the crest of one wave and the crest of the next wave is called wavelength.

spectrum If you shine white light through a prism, the light spreads out to make a range of different colors with different wavelengths, called a spectrum.

Key Terms: Examples:optical telescope

refracting telescope

convex lens

reflecting telescope

radio telescope

observatory

A telescope that uses lenses or mirrors to collect and focus visible light is called an optical telescope.

A refracting telescope uses convex lenses to gather and focus light.

A convex lens is a piece of transparent glass, curved so that the middle is thicker than the edges.

A reflecting telescope uses a curved mirror to collect and focus light.

Devices used to detect radio waves from objects in space are called radio telescopes.

An observatory is a building that contains one or more telescopes.


Links on Telescopes

Click the SciLinks button for links on telescopes.

- Telescopes


Telescopes

Click the Video button to watch a movie about telescopes.

- Telescopes


The Hubble Space Telescope

Click the Video button to watch a movie aboutthe Hubble Space Telescope.

- Telescopes


End of Section:Telescopes


Star Size

- Characteristics of Stars

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.


Star Spectrums


Astronomers use line spectrums to identify the chemical elements in a star. Each element produces a characteristic pattern of spectral lines.


Parallax


Parallax is the apparent change in position of an object when you look at it from different places.


Measuring Distances to Stars


Astronomers often use parallax to measure distances to nearby stars.


The Hertzsprung-Russell Diagram


Astronomers use H-R diagrams to classify stars and to understand how stars change over time.


What You Know

What You Learned

Using Prior KnowledgeBefore you read, write what you know about the characteristics of stars in a graphic organizer like the one below. As you read, write what you learn.

1. Stars are bright and hot.2. Distances between stars are often measured in light-years.3. The sun is a yellow star.

1. Stars are classified by color, temperature, size, composition, and brightness.

2. Light travels 9.5 million million kilometers in one year.3. The sun has a surface temperature of about 5,800ºC.



More on Types of Stars

Click the PHSchool.com button for an activityabout types of stars.



End of Section:Characteristics

of Stars


The Lives of Stars

- 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.


The Lives of Stars Activity

Click the Active Art button to open a browser window and access Active Art about the lives of stars.

- Lives of Stars


Black Holes

- Lives of Stars

The remains of the most massive stars collapse into black holes. Here, a black hole is shown pulling matter from a companion star.


SequencingAs you read, make a flowchart that shows the stages in the life of a star like the sun. Write each step of the process in a separate box in the flowchart in the order that it occurs.

Life Cycle of a Sun-Like Star

Protostar forms from a nebula.

A star is born as fusion begins.

The star stays on the main sequence for billions of years.

The star begins to run out of fuel.

The star becomes a red giant, then a white dwarf, then a black dwarf.

- Lives of Stars


End of Section:Lives of Stars


Structure of the Milky Way

- Star Systems and Galaxies

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.


Scientific NotationThe 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 numberis 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



Scientific Notation

Practice Problem

The sun takes about 220,000,000 years to revolve once around the center of the galaxy. Express this length of time in scientific notation.

2.2 X 108 years



Building VocabularyCarefully read the definition of each Key Term. Also read the neighboring sentences. Then write a definition of each Key Term in your own words.


Key Terms: Examples:binary star Star systems that have two stars are called double

stars or binary stars.

eclipsing binary An eclipsing binary is a star system in which one star cannot be seen at times because the other star blocks the light.

open cluster Open clusters have a loose, disorganized appearance and contain no more than a few thousand stars.

globular cluster Globular clusters are large groupings of older stars.

Key Terms: Examples:galaxy

spiral galaxy

elliptical galaxy

irregular galaxy

quasar

A galaxy is a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.

Spiral galaxies appear to have a bulge in the middle and arms that spiral outward, like pinwheels.

Elliptical galaxies look like round or flattened balls.

Irregular galaxies do not have regular shapes.

Since quasi means “something like” in Latin, these objects were given the name quasi-stellar objects, or quasars.

Key Terms: Examples:universe

scientific notation

Astronomers define the universe as all of space and everything in it.

Scientific notation uses powers of ten to write very large or very small numbers in shorter form.


Links on Galaxies

Click the SciLinks button for links on galaxies.



End of Section:Star Systems and Galaxies


Retreating Galaxies

- The Expanding Universe

All distant galaxies are moving rapidly away from our galaxy and from each other.


Speeding Galaxies

Use the graph to answer the questions about moving clusters of galaxies.



Speeding Galaxies

About 2.5 billion light-years; about 39,000 km/sec

Reading Graphs:

How far away is the Bootes cluster? How fast is it moving?



Speeding Galaxies

Hydra; Virgo

Reading Graphs:

Which galaxy is moving away the fastest? Which galaxy is closest to Earth?



Speeding Galaxies

The greater the distance from Earth, the greater the speed of the galaxy.

Drawing Conclusions:

How are the distance and speed of a galaxy related?



Speeding Galaxies

Its speed would be about 80,000 km/s.

Predicting:

Predict the speed of a galaxy that is 5 billion light-years from Earth.



Moving Galaxies


The galaxies in the universe are like the raisins in rising bread dough.


Formation of the Solar System


The solar system formed from a collapsing cloudof gas and dust.


As you read, identify the evidence that supports the big bang theory. Write the evidence in a graphic organizer like the one below.

Theory

Evidence

Big Bang

Moving galaxies: Allgalaxies are moving away

from us and from one other.

Cosmic backgroundradiation: This glow comes

from thermal energy leftover from the big bang.


Identifying Supporting Evidence


Links on the Expanding Universe

Click the SciLinks button for links on the expanding universe.



End of Section:The Expanding

Universe


Graphic Organizer

Telescopes

On Earth

Radio waves

can be

Visible light

collect types of radiation

Infrared

In space only

UltravioletGamma

rays

collect types of radiation

X-rays


End of Section:Graphic Organizer

Documents

Stars, Galaxies, and the Universe Telescopes Characteristics of Stars Lives of Stars Star Systems and Galaxies The Expanding Universe Table of Contents