1. Introduction to space and things in it
THE UNIVERSE
Introduction to space and things in it

2. Universe -
All matter and energy that exists, that has ever existed and that ever will exist.
It is EVERYTHING and there is only ONE universe.
The universe is approximately 15 billion years old!

3. Stars - Huge balls of hot gas that emit light.
That’s all stars are – gas! Mainly hydrogen and helium.
The light that is emitted is why stars appear to “twinkle”.

4. Galaxy –
A collection of millions and billions of stars bound together by gravity.
There are different types of galaxies we will talk about.

5. Light year -
A unit of distance equal to the distance light travels in one year.
The universe is so large that we have to use very large units to measure it.
A light year = 9.5 x 1015 m. This distance is so large that it would take 10 million years to drive it in a car!

6. Can you imagine just how large the universe is?
One thing to understand is what we see in the universe (starlight, sunlight, etc.) happened in the past.
For instance, when we go outside on a sunny day, the light that hits your skin left the sun more than 8 minutes earlier.
The nearest stars to the Earth are 4.3 light years away! So the light we see from those stars left them 4.3 years ago.

7. More about galaxies We live in the Milky Way galaxy.
Anyone know why it is named that?
It is because in ancient times our galaxy looked like a radiant band of light flowing like a river of milk.
The Milky Way is stars, gases, and dust. This is called interstellar matter and provides the material to form new stars.

8. Galaxies
As of now, astronomers estimate that the universe contains over 100 billion galaxies. If you counted 1000 new galaxies a day, it would take 275,000 years to count them all!

9. 3 types of galaxies Galaxies are classified based on SHAPE
1. spiral – have spiral arms, bluish tint, a lot of gas and dust.
These are the youngest galaxies – the bluer the color the younger they are.

10. 2. elliptical – these are shaped like a flattened oval.
They are older than spiral with old stars and little gas and dust (so they cannot make many new stars).
They are more red in color.

11. 3. Irregular – these have no definite shape, just “blob-like”.
Some have gas and dust, some do not. Meaning some have stars and some do not.
Can vary in age.

12. Galaxies Gravity holds galaxies together in clusters.
Cluster – a group of galaxies bound together by gravity.
The Milky Way and its neighboring galaxy, Andromeda, are only 2 in a cluster of This is called the “Local Group” and more galaxies are being discovered as better telescopes become available.