Page 19 - Unit 1-4

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Exercise 1-2
1 B 14 billion years ago
2 B millions

Background information
A galaxy is a group of many stars,
along with gas, dust, and dark
matter. The name ‘galaxy’ is taken
from the Greek word galaxìas
meaning ‘milky‘, a reference to
our own galaxy, the Milky Way.
It contains over 200 billion stars,
including our Sun. The Milky Way
has a diameter of 100,000 light
years, and is a barred spiral galaxy.
The discovery of the Milky Way
goes back to the Ancient Greek
philosopher Democritus. It has three
main parts: a disk, in which the Solar
System resides, a bulge at the core,
and an all encompassing halo.
This galaxy belongs to the Local
Group of three large galaxies
and over 50 smaller galaxies. The
Milky Way is one of the largest
galaxies in the group, second to
the Andromeda Galaxy that moves
towards the Milky Way Galaxy, and
will meet it in about 3.75 billion
years.

Exercise 3 Glossary
1 To see the distant stars and to know more
facts about the universe. priests = นักบวช
2 10 billion stars.
3 The universe.
4 It began after a sudden big explosion.
5 The Milky Way.
6 There are millions of galaxies.

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