Unit D, Chapter Four:

1. Unit D, Chapter Four: Exploring the Universe

2. Science Question of the Day… • How does a telescope work?

3. Stars • Stars, like everything else in the Universe, have life cycles. • They don’t live forever; they live as long as their supply of hydrogen, helium, and other fuels last. • Of course, there is a process for using this energy, and they produce a product we need for life: light.

4. The Brightness of Stars • Stars appear to be small spots in our night sky. • Some seem very bright, and others seem to be very dim. • In reality, from Earth we cannot tell exactly how brightly or dimly stars shine because we are too far away. • This is why we measure starlight in two ways: how bright a star appears from Earth, and how bright it actually is.

5. The Brightness of Stars • How bright a star appears from Earth is called its apparent magnitude. • By using this scale, our Sun is the brightest star in the sky, but that is because it is so close. • It shines so brightly to us that no other stars can be seen during the daytime hours. • Many stars that look dim are actually much brighter than our Sun, but they seem dim because they are so far away.

6. The Brightness of Stars • The actual brightness of a star (not based on distance) is called its absolute magnitude. • Absolute magnitude is not concerned with distance. It instead measures the light that is given off by a star. • On the absolute magnitude scale, lower numbers indicate stars that shine very brightly. • Our Sun is approximately a 4; however, there are stars close to our solar system that go as low as -25!

7. Types of Starlight • We cannot visit stars for obvious reasons, so what we know about stars we have learned through observing their electromagnetic radiation. • Electromagnetic radiation (ER) is energy that travels through space in waves. • Light is an example of ER, but there are many others like radio waves, infrared rays, visible light, ultraviolet rays, X rays, and gamma rays. • Some stars no longer give off visible light, so we have to detect them using radio waves and other types of ER.

8. Birth and Death of Stars • We think of life in terms of decades, and, if we are lucky, centuries. • Stars may live for billions of years before their demise. • We have not observed a complete life cycle of a star from birth to death, but we have seen many in various stages. • This has helped us to develop an explanation of how stars form, how they change, and how they die.

9. Birth and Death of Stars • Stars form in huge, cool, dark clouds called nebulae. • Gravity causes parts of the nebulas to come together. • The gases and dust form dense centers called protostars. • When the protostar has enough mass, pressure causes the temperature in the core to rise high enough for fusion to begin. • This is the beginning of a star.

10. Time for a little practice… • Read, “Nebulae” and answer questions 1-4 for homework tonight. • Here’s a good joke… • Q. Why wouldn’t you want to give Saturn a bath? • A. It would leave a ring around the tub.

11. Science Question of the Day… • Sometimes our cars run out of gas, and what happens? They stop running! What do you think happens when a star runs out of fuel?

12. Types of Stars • We know that starts emit light and energy, but how do they do that? • A star’s energy comes from fusion, a process in which nuclei of atoms are joined. • In most stars, hydrogen and heat are the fuel for fusion. • Sometimes you can tell how hot a star is just by looking at its color. • The coolest stars are red, the average temperature stars are yellow, and the hottest stars are blue.

13. Birth and Death of Stars • The temperature at which a star starts its life effects what kind of star it will become.

14. Birth and Death of Stars It may start as a hot blue star, or a high-mass star: - biggest - hottest shortest life uses hydrogen quickly star swells to a supergiant explodes into supernova core may collapse becomes a neutron star or a black hole

15. Birth and Death of Stars It may start as an average yellow star: - medium size - average temp 10 billion year life star swells to a red giant collapses after a long time throws off gases that become a planetary nebula becomes a small, dense, white dwarf

16. Birth and Death of Stars It may start as a cool red star: - small - cool temp uses hydrogen slowly 30 billion years of life fusion will eventually stop becomes a small, dense, white dwarf sometimes these stars will flare and become very bright for a few weeks this is called a nova

17. Stars Life Cycle • Insert movie “The Life Cycle of Stars”

18. Time for a little practice… • Read, “The Stars” and answer questions 1-5 for homework tonight. • Here’s another good joke… • Q. What kind of star wears sunglasses? • A. A movie star

19. Science Question of the Day… • Think about the stars we discussed yesterday. What kind of star do you think our sun is? How do you know? How will our sun die?

20. Interesting Oddities • Stars are pretty cool (or hot I guess), but there are other interesting objects in space that are like stars or are even remnants of stars: pulsars, quasars, neutron stars, and black holes.

21. Your Task • Today, you and a partner will research one of the oddities listed on the previous page and share your information with the rest of your group. • Answer the questions on your handout by completing online research. • Remember CARS!!! • We will report back on what we have learned at the end of class. • Check my website for helpful websites! You may use these, but you must use one other source and tell me where you got your information!

22. Science Question of the Day… • Let’s change this around a bit. I want you to tell me what questions you have about space. Please come up with at least one question (and try to think of an answer too) that you have about astronomy.

23. Galaxies • We know that there are stars in space, but other stars (like our Sun) live in solar systems and galaxies like our Milky Way Galaxy. • There are more than 200 billion stars in our galaxy alone. If our solar system were a plate, the Milky Way would be the size of the United States. • A galaxy is a large system of stars, and for a long time, people thought the Milky Way was the only galaxy.

24. Galaxies • Edwin Hubble observed the Andromeda Galaxy in 1923 which proved that we were not the only galaxy.

25. Edwin Hubble • Insert video “Hubble Telescope, VLTs, and Current Technologies”

26. Types of Galaxies • Galaxies are classified by shapes: spirals, barred spirals, ellipticals, and irregular clusters.

27. Spiral Galaxies curved arms of gases rotate around bulging center gases surround galaxy in a sphere center is red, contains red giants in later stages of life arms are blue, contain young stars at the beginning of life

28. Barred-Spiral Galaxies similar to spiral arms trail from two bar-shaped clusters of stars that extend from the core

29. Elliptical Galaxies: Ball Shaped, and Egg Shaped most common type of galaxy much smaller than spirals rotate, but much more slowly than other types of galaxies

30. Irregular Galaxies smallest group of galaxies loose collections of stars in clouds of gas and dust no regular shape

31. Types of Galaxies • Insert Video “How the Universe Works: Alien Galaxy”

32. Time for a little practice… • Read, “Galaxies” and answer questions 1-3 for homework tonight.

33. Science Question of the Day…

34. Space Exploration • Since prehistoric times, people have been looking at the sky and looking for answers. • However, in more recent times (1600s to present) we have been able to observe not only what we can see with our naked eye, but also what we can’t see. • Earlier in this unit, we discussed telescopes and the use of them by scientists like Edwin Hubble to view space. • Let’s take a closer look at telescopes… • Get it, a closer look… I crack myself up…

35. Telescopes • Galileo did not invent the telescope, he improved on it. The telescope he improved upon is called a refracting telescope. • Refracting telescopes use glass lenses to gather light and magnify objects.

36. Telescopes • About 60 years later, Isaac Newton invented a reflecting telescope that used mirrors to gather light and magnify images. • This allowed scientists to see even farther into space.

37. Going to Space • By the 1800s, people no longer wanted to observe space from the ground; they wanted to go there! • In 1926, Robert Goddard successfully tested a rocket that could reach space with a fuel mixture of liquid fuel and oxygen. • The United States and the Soviet Union were quickly locked in the Space Race. • The Soviet Union beat us with the launching of the first satellite, Sputnik I.

38. The Space Race • Insert video “The U.S.-Soviet Space Race and the Future of Rockets”

39. People in Space • President Kennedy was a proponent of sending astronauts to space for exploration purposes. • He challenged Americans to put a man on the Moon by the end of the 60s. • The Mercury Program began by shooting small rockets into space with people onboard orbiting the Earth and coming back. • During the Gemini Program, NASA experimented with heavier loads for longer periods of time.

40. People in Space • The Apollo program was designed to put man on the Moon. We achieved our goal on July 20, 1969. • The space program now depends on the space shuttle, a reusable vehicle that goes into orbit like a rocket and then glides back to Earth like an airplane.

41. Space Program • Insert Video, “The Spacefiles: Exploration: A History of Space Flight”

42. Space Probes • NASA is not only concerned with putting humans into space; they also want to find out more about space that we cannot currently visit with our technology. • We have sent satellites and probes to planets and moons for over 50 years. • The probes send back images and data that we would otherwise never be able to see.

43. Space Probes • Insert Video, “Observing from Space”

44. Advanced Telescopes • As well as sending probes and satellites into space, we have also sent advanced optical telescopes. • These telescopes can see farther into space then we have ever been able to see before. • The Hubble Space Telescope is an example of an optical telescope.

45. Radio Telescopes • Optical telescopes can’t see light outside of the visible spectrum like X-rays and radio waves. • We have radio telescopes to help us collect these kinds of waves from space. • In 1980, scientists built the Very Large Array in New Mexico to listen to radio waves in space.

46. To sum up… • The Universe is a pretty big place. • There is a lot more to it than what we can cover in two weeks of class. • You will be researching something of interest to you in the Universe. It can be anything except planets (moons other than ours are acceptable). • You will create a model that will be shared with the class. • Have fun exploring!