Lesson #13 Topic: The Earth, Sun, and Solar System

1. 10/3/06 Lesson #13Topic: The Earth, Sun, and Solar System Objectives: (After this class I will be able to) Explain why the earth experiences different seasons Research information about our solar system Create a scale model of our solar system Warm Up: Explain why the weather is changing from summer to fall. Assignment: 1 page planet paper (1 per team) due Thursday, Concept development 13.3 & 14.1 due Friday

2. Why does the Earth have seasons? • The Earth’s axis is tilted at a 23.5° angle. • This results in some regions of the earth receiving direct sunlight only part of the year. • Direct sunlight will have a higher concentration of light per area. *Flashlight Demo* • Direct sunlight has less atmosphere to travel through, therefore less energy is absorbed by air. • Winter regions have longer periods of darkness than light, therefore having more time to cool and less time to warm. The opposite is true for summer regions. Winter Summer

3. Solar System Project • You and your partner are to research a planet chosen by your instructor. • The two of you will write a 1 page paper answering the following key questions. • You will then present your information to the class and create an appropriate scale model of your planet to be used in a scale model of the solar system. • You will be graded on how well you are able to answer the following questions in your paper as well as in your presentation.

4. Solar System Project • How far away is the Sun from your planet? • What is the mass of the planet? • What is the composition of the surface and atmosphere? • What is the average surface temperature during day and night? • What is the period of revolution? • What is the period of rotation? • If the Sun had a diameter of 238mm, how far away would this planet be and what would be the size of the planet?

5. Website Fun http://www.exploratorium.edu/ronh/solar_system/http://www.bradley.edu/las/phy/astronomy/about_solar.htmlhttp://liftoff.msfc.nasa.gov/academy/space/solarsystem/solarsystemjava.html

6. 10/6/06 Lesson #14Topic: Stars, Galaxies, and the Universe Objectives: (After this class I will be able to) Explain stellar evolution Describe galaxies and other extragalactic entities Describe a light year, a parsec, and how intergalactic distances are measured Communicate and discuss basic cosmology Warm Up: In your opinion, is the earth big? Assignment: “Exam Review” due at the end of the period on Tuesday

7. How big is BIG?

8. How big is BIG?

9. How big is BIG?

10. How big is BIG?

11. How big is BIG?

12. So how do we measure BIG? • Ok, so I get the idea of big, but how do we measure such large distances? • One way is to use the idea of time and velocity as a distance. d = vt • The speed of light works nicely because it is a constant and it is very very very fast. • Earth years work nice too, because we live on earth, and to us, a year is a long time. • A light-year is the distance light travels in a year. • How many km is a light-year? c = 3x108 m/s

13. So how do we measure BIG? • Another way to measure is by use of parsecs. • A parsec is a parallax angle in seconds of arc. (degrees can be broken down into subunits of minutes and seconds) A second = 1/3600th of a degree. Star Φ D d θ Earth Earth’s orbit Sun

14. So how do we measure BIG? • Using basic geometry… So…… We can use tanΦ≈ Φ since Φis very small. A parsec is measured as 1/Φ,where Φis measured in seconds (“) 1pc = 3.26ly Star Φ D d θ Earth Earth’s orbit Sun

15. Stars • There are more stars in the sky than grains of sand in the entire world. • We will see that stars come in all sorts of sizes, masses, colors, temperatures, and brightness. • We’ll start with our own star, the Sun. • The sun is a very typically average star (thank goodness).

16. Fun Sun Facts • Diameter = 863,040 miles; 109 x Earth • Mass = 328,000 x Earth’s mass • Volume = 1.3 million times Earth’s volume • Surface Temperature = 9,932°F • Core Temperature = 27,000,000°F • Rotation period = 27.28 days • Cosmic year = 225 million years • Estimated age = 4.6 billion years

17. Stellar Evolution: A star’s life story • Stars are born from clouds of gas and dust that makes up a high proportion of the material found in normal galaxies. • These clouds of gas and dust are called nebulae. • Gravitation pulls this matter in tighter and tighter into distinct large and separate clumps. • These clumps form into stars. • The brightness, temperature, and color of each star depends on how much mass is in the clump.

18. Stellar Evolution: A star’s life story • The intense gravitational force from the gigantic mass creates enough pressure on the gas (hydrogen) at the center of the star to begin undergoing nuclear fusion. • The atoms are literally squished together to form new denser atoms (helium). • This reaction gives of a tremendous amount of energy which causes it to occur even more frequently. (a chain reaction)

19. Stellar Evolution: A star’s life story • The star is in a constant battle of trying to explode and implode at the same time. • The nuclear reaction in the core makes it want to explode. • The intense gravitation makes it want to implode. • This results in a balance that we currently have occurring in our star. • When a star reaches this point it has entered the main sequence of stars.

20. Stellar Evolution: A star’s life story • The main sequence is where a star will spend the majority of its life. • Main sequence stars are of average temperature, brightness, and size. (Dwarfs) • Our Sun will continue to burn hydrogen for another 5 billion years or so until it starts getting low on hydrogen and high on helium • As the core of the star gets more and more helium, and denser and denser, gravity gets even stronger and the temperature gets hotter and hotter. • This increases the rate of fusion, and the exploding core starts win against gravity.

21. Stellar Evolution: A star’s life story • The star blows up to thousands of times its original size to what is called a red giant. • The decrease in pressure allows for cooling on the surface which gives it its red color. • Our Sun will one day blow up to the point where its outer surface will consume the Earth. • Fusion continues even though we’re out of hydrogen… we’re now fusing 3 helium atoms at a time into even denser carbon atoms. • Carbon atoms start fusing into even heavier atoms like iron and nickel.

22. Stellar Evolution: A star’s life story • The reactions of these heavy metals require energy rather than give off energy. • The decrease in energy allows gravity to start to win the battle, and the star implodes. • Stars like our Sun will then retire as a white dwarf, a tremendously dense and hot star about the size of the Earth. • When the star finally runs out of energy it becomes a black dwarf, a dark cold hunk of ash. • Stars more massive than our Sun may collapse and become neutron stars or black holes.

23. Stellar Evolution: A star’s life story • Some stars have enough mass and become dense enough, such that the intense gravitation causes the electrons of the atoms to “reverse decay” and combine with protons to form neutrons. • These neutron stars are no longer made of atoms, just neutrons. • A neutron star will eventually reach critical density and a supernova will occur. • The star blows up and becomes a new nebula of all sorts of matter. (Perhaps a way we came about having all the convenient elements we have here on earth.)

24. Stellar Evolution: A star’s life story • Some stars have enough mass and become dense enough that the gravitational force (at this point) is stronger than even the strong nuclear force. • No explosion can occur because nothing can escape from this point in the universe, not even light. • This is referred to as a black hole. • Our Sun is not massive enough to become a black hole, but if it we’re to happen all of the sudden, would the Earth be sucked into it?

25. H-R Diagram

26. Galaxies • Our galaxy is of course the Milky Way • It has a diameter of 100,000 ly and a thickness of 2000 ly. • It is a spiral galaxy with a bulging nucleus. • It contains about 1011 stars. • There are also about 1011 observable galaxies from Earth. Some of these galaxies are clumped close together in superclusters much like stars are clumped close together within galaxies.

27. Telescopes or Time Machines? • When you look up into the night sky, you are actually looking millions of years into the past. • The light that is reaching the earth from distant stars has traveled for so many years, that the star you are looking at may not even exist anymore! • In fact, the further and deeper you look into space, the further you look back into time. • Far enough that we can begin to put together a good idea of the origin of the universe, and theorize where the universe is headed.

28. Cosmology • Cosmology is the study of the universe. • Is the Universe infinite, or finite? If it is finite what is outside of it? If it is infinite, has it always been expanding? • It deals especially as a search for a theoretical framework to understand the observed universe, its origin, and its future. • Discuss the early history of the universe and its support from cosmic microwave background radiation. • Discuss the expansion of the universe. • Discuss the open, flat, closed, and cyclic universe theories.