1. The Formation of Stars

2. The Emptiness of Space? It was once thought that the space between stars in our galaxy was empty. What we now know is much different.

3. The Emptiness of Space? The space between stars is filled with gas, dust, solar wind from other stars, and more.

4. Discovery It took scientists hundreds of years to finally understand. At that same time theories were developed around the formation of stars and planetary systems such as our own.

5. Let’s Pause… And read page 474.

6. Theory of Star Formation – You be the Scientist Please turn to p.476 in your texts. This activity will give you a small insight into what scientific theorizing is all about.

7. The Solar Nebula Theory This theory best explains how our sun and planets formed.

8. The Solar Nebula Theory Scientist calculate our sun to be about 5 billion years old. Some of the oldest rocks found on Earth are about 3.5 billion. This fits with the theory.

9. A Cloud of Gas More than 5 billion years ago our solar system was nothing more than a huge cloud of swirling gas and dust.

10. Gravity At Work Particles in this cloud came together because of the force of gravity.

11. Gravity at Work Eventually temperatures at the center of the cloud reached a point where fusion occurred. Our sun was born.

12. Other Spheres Form In the accretion disc around the new star, other spheres began to form. These would become the planets.

13. It’s Hot Near the Center The spheres near the new star were subjected to extreme radiation. These inner planets did not have enough gravity to hang on to their thick gaseous atmospheres and they were literally blown away, leaving rocky spheres.

14. Things Start to Cool Down Slowly temperatures began to cool. Water began to condense on Earth. Eventually life would form there.

15. Catastrophic Theory Another theory suggests the planets were created in another way. It states that the sun collided with another large body, most likely another star.

16. Catastrophic Theory It was this collision that provided the matter to form the other planets.

17. Evidence for the Solar Nebula Theory Despite there being competing theories, there is strong evidence to support the Solar Nebula Theory.

18. More Evidence Photos of accretion discs around new born stars strongly suggest the Solar Nebula Theory is correct.

19. Other Planets Out There? Other solar systems means the possibility of other planets. In fact we’ve found some. Quite a few in fact, 726 as of January, 2012.

20. Extra-Solar Planets What might these new planets look like? Is there life here? At this point it is all just speculation.

21. Extra Solar Planets The photo to the right shows three extra solar planets around the star HR 8799.

22. Homework Please finish reading section 14.3 Answer question #1-5 and 7. Vocabulary  Inter-Stellar Medium  Solar Nebula Theory  Extra-Solar Planets