Galaxies

The universe is a huge open space made up of billions of galaxies and an even larger number of stars. Our galaxy is called the Milky Way. Our solar system, including the Sun, the planets
and their moons, forms just a tiny part of the Milky Way.






Q How was the universe formed?

A The universe was born more than

15 billion years ago. It is believed that the

universe began as a small ball of fire. This

fireball grew larger and larger until one day it

exploded, to form the universe that we know.

Q How big is the universe?
A No one knows how big the universe
really is. There are at least 100 billion
galaxies that we know of. However, this
number keeps growing as better telescopes
are developed and we see more and more
galaxies. On top of that, the galaxies are
moving away from each other, causing the
universe to expand. Some scientists believe
that the universe will never stop expanding,
while others think that one day it will begin
to shrink until it becomes a fireball again.


Q What is a galaxy?
A A galaxy is a group of billions of stars,
dust and gas bound together by gravitational
force. A galaxy can either be on its own or in
a cluster. Galaxies come in different shapes
and sizes. Scientists have divided them into
three categories based on their shapes – spiral,
elliptical (oval) and irregular (no shape).


Q How did the Milky Way get its name?
A In ancient Greek and Roman myths, it was
believed that the goddess Hera (Juno) spilt
milk across the sky and called the white streak
it left a ‘river of milk’. The Romans called it
Via Lactea or a ‘road made of milk’. This is how
our galaxy came to be named the Milky Way.
Q Is the Milky Way a part of a cluster

of galaxies?
A The Milky Way and three of its
neighbouring galaxies are part of a larger
cluster known as the Local Group (because
they are closest to Earth). The neighbouring
galaxies in the Local Group are called
Andromeda, and the Large and
Small Magellanic Clouds. Of the
35 galaxies in the Local Group,
only these three can be seen
with the naked eye.




A galactic crash
Sometimes, galaxies crash into one another due to the force of
gravity. But the stars in them are too far apart to cause any real
damage. Our own galaxy is on a collision course with its neighbour
Andromeda. The collision will take place in about five billion years
and the two will merge to form an elliptical (oval) galaxy.