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.
Quick Q’s:
1. What is the Big
Bang theory?
The Big Bang theory
suggests that the
universe as we know
it today was created
after a huge explosion
or ‘bang’. Georges
Lemaitre proposed
the theory of the
Big Bang in 1927, and
in 1929 Edwin Hubble
expanded on his work.
2. Which is the
largest galaxy?
Scientists do not know
exactly. The largest
galaxies we know of are
giant elliptical (oval)
galaxies located in
the middle of a whole
group of galaxies.
One of the largest
is in the central
galaxy in the cluster
Abell 2029.
3. How big is the
Milky Way?
The Milky Way is huge.
It takes the Sun about
250 million years
to orbit once around
the centre of the
Milky Way.
4. What is Messier
Object 31?
The Andromeda
Galaxy is also known
as Messier Object 31,
or M31. This galaxy
is more than twice the
size of Milky Way. But
it is still not the largest
galaxy we know of.
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.
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