1. The Basic Structure of the Universe

2. What is the Universe? All matter and energy, including the earth, all the galaxies, and the contents of intergalactic space, regarded as a whole.

5. The Speed of Light  Light is a form of Electromagnetic Radiation  Light is a wave and a particle (packet of waves)  Light has a constant speed c  186,000 miles per second  299,792,458 meters per second  All radiation moves at this speed in a vacuum  Radio waves - Cell phones, X-rays, UV – suntans

6. Time and Light When we look out at the Universe we are looking back in time. –The nearest star is 4.3 light years away. –The distance to the galaxy M87 in the Virgo cluster is 50 million light years. –The distance to most distant object seen in the universe is about 13 billion light years.

7. A measure of Distance and of Time 3 lightminutes

8. Galaxies Near and Far Messier 106 Distance: 21 million light-years Hubble Ultra Deep Field Distance: 13 billion light-years

9. What is a galaxy? A galaxy is a collection of stars, dust, and gas bound together by gravity.

12. Elliptical Galaxies

13. Irregular Galaxies

14. Spiral Galaxies

15. We are part of the Milky Way spiral galaxy. It contains between 200 and 400 billion stars, one of which is our sun. That means our entire Solar System is just a dot at the end of the arrow above! It takes light about 100,000 light-years to travel the diameter of the galaxy.

16. The Milky Way

17. The Andromeda Galaxy is the closest large galaxy and looks a lot like our Milky Way Galaxy. It is 2.2 million light years from Earth! Other smaller galaxies are anywhere from 50,000 to several hundred thousand light years away.

18. We live in a Solar System. Our solar system includes the sun, all eight planets, the “dwarf planet” Pluto, and many smaller objects such as moons and asteroids. Remember: Our entire Solar System is just a dot in the Milky Way Galaxy!

19. Our Solar System Asteroid Belt

20. Most of these pictures were taken with the Hubble Space Telescope in orbit around our planet. It is 575 km (360 miles) above Earth and traveling at 7,500 m/s. It orbits the Earth every 97 minutes.

21. Structure of the Universe: Think of it this way! Universe Science Book Galaxies Chapters Solar SystemsSections Planets Sub-Sections Earth One of the Sub-Sections