Galaxies Task 1 Pre- reading Activity

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Grade 9 Science Related Reading/Earth and Space

Grade 9 Earth and Space

9E.1: The Visible Universe


Task 1 - Pre- Reading Activity

This picture is taken from Phillip Island, Victoria, Australia. Guess what is it?

milky way.jpg

Explain How do scientists

estimate how many stars a

galaxy has?


Task 2 – Reading Activity

What Is a Galaxy?

If you look out on a clear night far from city lights, you

can see hundreds of stars. Many of these stars are part

of our galaxy, which is called the Milky Way. Our galaxy

actually contains many more stars than you can see.

A galaxy is a large group of gas, dust, and millions of

stars. The biggest galaxies contain more than a trillion

stars. Scientists can’t actually count the stars, of course.

They estimate how many stars are in a galaxy by measuring

the size and brightness of the galaxy. The bigger and

brighter the galaxy, the more stars it has.

Galaxies come in different shapes and sizes. Scientists

classify galaxies by shape. The four most common types

of galaxies are spiral, elliptical, irregular and lenticular.


A spiral galaxy has two parts: a central bulge and

arms that form a spiral around the center. The bulge is a

dense group of old stars. The arms are made of gas, dust,

and much younger stars.

The Milky Way is a spiral galaxy. Our sun is one of the

200 billion stars in the Milky Way. From Earth, the edge

of the Milky Way looks like a bright belt of stars that

stretches across the night sky.

An elliptical galaxy is made of many stars and looks

like a snowball. Elliptical galaxies are among the largest

galaxies in the universe. Some may contain as many as

5 trillion stars! There is very little free gas in an elliptical

galaxy. Therefore, few new stars form there.


An irregular galaxy has no clear shape. It may have as

few as 10 million or as many as several billion stars. Some

irregular galaxies form when two other galaxies collide.


Lenticular galaxies are sometimes called "armless spiral galaxies."

Lenticular galaxies have a central bulge, but no spiral arms. Just like

spiral galaxies, some lenticular galaxies have a bar, they are called

"barred lenticular galaxies"

Galactic mash up

Save the date: The Milky Way will merge with its nearest large neighbor in about 4 billion years

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By: Stephen Ornes / June 18, 2012

By Stephen Ornes / June 18, 2012

A show of swirling lights will fill the night sky as the Andromeda galaxy collides with the Milky Way in 4 billion years. Since you won’t be there to see it, here’s an artist’s illustration of what the mash up might look like.

The Andromeda galaxy, our nearest large galactic neighbor, is headed straight for the Milky Way, our home galaxy. The collision is inevitable. But don’t worry, you won’t be around to see it.

Gravity pulls Andromeda toward the Milky Way at a brisk 250,000 miles per hour (or roughly 400,000 kilometers per hour). That’s fast enough to get from Earth to the moon in about an hour. But even at that speed, the galactic merger won’t occur for another 4 billion years.

The cosmic forecast was issued by astronomers at the Space Telescope Science Institute in Baltimore who studied stars in Andromeda. By tracking changes in the stars’ locations between 2002 and 2010, the scientists calculated how fast and in what direction Andromeda was moving. To view the stars, they used the Hubble Space Telescope, a school bus–sized telescope that orbits Earth, observing distant stars and galaxies.

Though the two galaxies will collide, the stars inside will likely survive. Every galaxy contains so much empty space between stars that it’s unlikely two stars would smash together. And though the sun and all its orbiting planets, including Earth, will probably end up in a new position, they won’t be destroyed. Eventually the galactic centers, each of which likely contains a super massive black hole, will combine into a single super massive black hole.

Until the new study, astronomers didn’t know if the Milky Way’s collision with Andromeda would be a glancing blow or head-on. Based on their calculations, the scientists predict that the merger will take about 2 billion years to finish, once it’s begun. That means the whole process won’t be completed until about 6 billion years from now — probably long after the sun runs out of fuel and swells to become a bright, cool star known as a red giant.

Collisions aren’t that unusual. Small, neighboring galaxies may merge to form galactic giants. And giants, like the Milky Way and Andromeda, may also smash into each other. The Hubble Space Telescope has recorded stunning images of these collisions in progress. Hubble data also suggest that such collisions happened more often long ago, when the universe was smaller and the galaxies were closer together.

Astronomers still don’t know, however, how often mergers occur. They want to know because galactic collisions may be an important contributor to how our universe developed.

Task 3 – Post Reading Activity
Q1: What four shapes can galaxies be?


Q2: What is a nebula?


Q3: Name two ways that spiral galaxies differ from elliptical galaxies.


Q4: How is a nebula different from a galaxy?

Q5: Circle the letter of the best answer for each question.

1. Which of the following binds a galaxy together?

a. dust c. stars

b. gravity d. gas

2. Which of the following is one of Edwin Hubble’s contributions to science?
a. He invented the telescope.

b. He developed a way to classify galaxies.

c. He founded the field of astronomy.

d. He built the Hubble Space Telescope.

3. Most galaxies are classified by their

a. shape. c. age.

b. size. d. color.

4. Where are newly formed stars found in a spiral galaxy?

a. spiral arms c. center bulge

b. spiral halo d. outer rings

5. What is the Milky Way thought to be?

a. a spiral galaxy c. a quasar

b. a round galaxy d. an odd-shaped galaxy

Q6: Read the description. Then, draw a line from the dot next to each description to the matching picture.

1. elliptical galaxy

2. irregular galaxy

3. spiral galaxy

Q7: Use the text “Galactic smash up” as reference and answer the following questions:

  1. What is the name of our nearest galaxy?


  1. What is Hubble?


  1. What can be the reason of collision of Andromeda and Milky Way galaxy?



  1. Approximately how much time is left for this collision?


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