05 The Milky Way

The Milky Way is one of many galaxies in the universe. This galaxy is shaped like a spiral and is home to our planet as well as the Sun. Earth is actually situated in an extension of the Milky Way — away from the centre.

There are more than 100 billion stars in the Milky Way and the centre cannot be seen because it is blocked by a lot of gas and dust. The Milky Way is so large that it takes light about 100,000 years to travel from one side to the other. It is one of many galaxies in the general area. These galaxies are known as a Local Group. The Milky Way is one of the three largest galaxies in its Local Group. In the centre of the Milky Way is a black hole that sucks up everything that crosses it. It is named for its milky appearance in the night sky.

The Milky Way is about 14 billion years old, and its oldest star is about 13 billion years old. It takes the Sun about 250 million years to orbit the Milky Way. The time it takes for the Sun to orbit the Milky Way is known as a galactic year. Until 1924, the Milky Way was the only known galaxy.

Word List

situated : referring to location

extension : a part that sticks out—not the main part

You Practice

I. By the numbers—What do these numbers mean in the reading?

1) 100 billion____________________________________________

2) 100,000 years__________________________________________

3) 14 billion years old_____________________________________

4) 250 million years_______________________________________

5) 1924_________________________________________________

II. Answer the following questions.

1) How did the Milky Way get its name?

2) How do we know that the Milky Way is very large?

3) What happens to things that go into the centre of the Milky Way?

4) What is a galactic year?

5) What is a local group?

III. True / False / Not Given—Write T if the sentence is true, F if the sentence is not true, or NG if there is no information about the sentence.

____ 1) The Milky Way is one of the smallest galaxies is its local group.

____ 2) The Earth is located in one of the main parts of the Milky Way.

____ 3) The Earth will soon fall into a black hole.

____ 4) The Milky Way probably looks like other galaxies.

____ 5) The Milky Way is shaped like a triangle.