Our Universe

What it is like, how we think it started, how it evolved to its

current state, and how it will end

Today we will talk about:

First, let’s look at some of the objects we might find if we explored our Universe

Where do we live?

Where is the Earth?

The Solar System

Q: What is a STAR?

Our Sun is a star!

Stellar Facts

• A star is a big ball of burning gas

• Our Sun is a very average star

• When we look out into the night sky, many of the stars we see are very similar to our own sun

• In fact some of these stars also have planets, just like our own Solar System

What is this?

What is it made of?

MANY STARS

MANY STARS

SOME SUN-LIKE

Galactic Facts

• Stars tend to group together to form galaxies

• Galaxies contain hundreds of thousands of stars

• At the centre of most galaxies is a massive black hole!

• Our sun is part of a galaxy

You are here!

Our Galaxy from the Earth

• We live on the Earth• The Earth is a planet in the Solar System,

orbiting our star which we call the Sun• The Sun is part of a galaxy• When we look out into the sky at night, all of

the stars we see are in our galaxy• But our galaxy, called the Milky Way is just

one of many…..

Galaxies: Hubble Space telescope image

‘Zoom out’ - galaxies form filaments and voids

• It is hard to comprehend the size of the Universe!

IN THE BEGINNING…….

EVERYTHING!

In the beginning, all the matter in the

universe existed in a incredibly hot and

dense state, represented here

by a tiny dot.

EVERYTHING!

About 14 billion years ago, the matter started expanding and from this hot, dense state. . .the universe was growing.

EVERYTHING!

ENERGY INCREASING, BECOMING LIKE A BOMB…….

STARTS EXPANDING…..

Tick tick tick……

BOOM!

The Big Bang

• Not really an ‘explosion’ • Universe expanded rapidly as a whole• (Universe is still expanding today as a

result of the Big Bang)• Matter was created in the form of tiny

particles (protons, neutrons, electrons)• Too hot for normal ‘stuff’ to form (eg

atoms, molecules)

COSMIC ‘SOUP’

The universe was a sea of tiny particles of matter.

PROTONNEUTRON

ELECTRON

COSMIC ‘SOUP’

Universe was too hot to support atoms.

• Universe much cooler, atoms start to form…..

• Hydrogen, Helium, normal ‘stuff’

300,000 Years Later…..

Universe is now a GAS

Universe is now a GAS

HYDROGEN

HELIUM

Gravitational Collapse

• We started with a uniform gas• Small regions became more dense due to the

attraction between the gas particles from gravity.

• The denser regions had larger gravity and started to pull other particles towards them

• The gaseous Universe began to look ‘clumpy’

GRAVITY!

Gravitational Collapse

• Regions with more particles (higher density) become gas clouds

• Gas clouds become stars and galaxies

• Galaxies congregate together in filaments, groups and clusters

We are inside one of these galaxies, so all we see are the nearby stars. We can see other galaxies if we use a telescope

The Gemini Telescope

Future?

• The Universe is still expanding

• All galaxies are moving apart

• The ‘explosion’ of the big bang is still happening!

• It may continue expanding forever

• Or it may stop expanding, and fall inwards in a big CRUNCH!

What have we learned?

• The Universe started with a BIG BANG

• Gradually the particles were drawn together under GRAVITY to form STARS and GALAXIES due to the force of gravity.

• Many stars have planets around them

• The fate of the Universe is uncertain…

THE END