28-1 A Closer Look at Light A. What is Light? a. Light-A form of Electromagnetic Radiation, which is energy that travels in waves. b. List some examples of electromagnetic radiation: c. How do they travel? How fast? d. What is the electromagnetic spectrum? See pg. 613. As a wave 300,000 km/s or 186,300 mph

28-1 A Closer Look at Light B. The Spectroscope a. Visible white light is made up various colors of different wavelengths. b. These are the colors of the rainbow. ROYGBIV c. What does a spectroscope do? It separates white light into its various wavelengths.

28-1 A Closer Look at Light C. Types of Visible Spectra a.   Three types of Spectra:           i.  Continuous-is an unbroken band of colors, which shows that its source is emitting light of all visible wavelengths.           ii.  Emission-a series of unevenly spaced lines of different colors and brightness.              

28-1 A Closer Look at Light            iii.  Absorption-a continuous spectrum crossed by dark lines. b.  A stars absorption spectrum indicates its composition.   www.classzone.com/books/earth_science/terc/content/visualizations/es2801/es2801page01.cfm?chapter_no=28

28-1 A Closer Look at Light D. The Doppler Effect a. What is the Doppler effect? b. What causes this? c. It can indicate the direction of a stars movement. The compression and stretching of waves

28-1 A Closer Look at Light d. A star moving towards the earth creates a shorter wavelength (blue in color). e. A star moving away from the earth creates a longer wavelength (red shift).

28-2 Stars and Their Characteristics A.   Early Observations a.   There are billions of stars in the sky. How far away is the closest star? b.   Constellations-Groupings of stars. Usually have ancient names. Human inventions. There are 88 constellations in the night sky. c.    What are some examples? d.    What causes the motion of constellations in the night sky?   Four light years Big Dipper, Orion, Gemini…. Rotation of the Earth

28-2 Stars and Their Characteristics   B.   Apparent Magnitude a.   It is the measure of how bright a star appears to be in the night sky. b.   The lower the magnitude number, the brighter the star is. c.   A first magnitude star is 100 times brighter than a sixth magnitude star.

28-2 Stars and Their Characteristics C.   Distances to Stars a.   How far is an astronomical unit? b.   Light year-Distance a light wave travels in one year or 9.5 trillion km. c.   What is parallax? Draw diagram on page 620. d. Parsec-Equal to 3.258 light years or 3.086x1013   150,000,000 km or the distance from the earth to the sun

28-2 Stars and Their Characteristics D.   Elements in Stars a.   A star is 69% Hydrogen and 29%Helium. Heavier elements makes up the remaining 2%. b.    Each star has a unique fingerprint. Why? Because it is made up of different combinations of gases and elements

28-2 Stars and Their Characteristics E.   Mass, Size, and Temperature of Stars a.   Mass can only be inferred. What are some factors that can help to determine mass? b.   Stars come in a wide variety of sizes. Some are smaller than the earth and others are 200 times larger than the sun. Composition and Gravitational Influence

28-2 Stars and Their Characteristics c.    Density also varies. One star near Sirius is so dense that one-teaspoon would weigh over a ton on earth. d.    Temperature and Color of Stars-A stars color varies depending on its surface temperature. See page 622.

28-2 Stars and Their Characteristics F.   Luminosity and Absolute Magnitude a.   Luminosity-the actual brightness. b.   Apparent Magnitude-How the star actually appears. c.   Absolute Magnitude-a measure of how bright the star would be if all stars were at the same distance.

28-2 Stars and Their Characteristics d.   Variable Stars-Show a regular variation of brightness over cycles. e.   Cephied Variables- Pulsating supergiants that have 5 day cycles (most of them). f. Eclipsing Binary-One star eclipses another.

28-3 Life Cycles of Stars 1. Hertzsprung-Russell Diagram a.   Why are stars like people? b.  The more massive they are, the shorter there life will be. c.   Plots luminosity of stars against their surface temperature. d.  Where do 90% of all stars fall? They come in different shapes, sizes, colors…

28-3 Life Cycles of Stars e. They fuse hydrogen into helium. f.     Giant Stars-High luminosity, 10-100 times bigger than the sun. g.  Super Giants-more than 100x bigger than the sun. low temperature, high luminosity. h.  White Dwarfs-Near the end of their life cycle. Once were red giants, now they are just the glowing core. Hot and dim.

28-3 Life Cycles of Stars 2. Birth of a Star a.   Nebula-Cloud of gas and dust that stars form from. What is it made up of? b.  What has to happen for fusion to begin? 99% Hydrogen & 1% dust Shock Wave… Gravity…Friction… increase in Temperature

28-3 Life Cycles of Stars 3. Death of a Star Like the Sun & Massive Stars When does a star start to die? b. What creates a planetary nebula? See diagram on page 628-29. c. What does the explosion of a supernova produce? When it runs out of Hydrogen The blown off gases Neutron Star or a Black hole

28-4 Galaxies and the Universe Remnants of Massive Stars Neutron Star- 20 km in diameter, trillions of times more dense than the sun. Pulsar-Rapidly spinning neutron star that emits pulses of radiation. Black hole- Incredibly dense remnant of a star. Gravitational force is so strong that light cannot escape. What are Galaxies? Systems containing billions of stars

28-4 Galaxies and the Universe How old is the Universe? b. Galaxies-systems containing millions or even billions of stars. It is estimated that there are between 50 and 100 billion galaxies. Which galaxy do we belong to? d. What are the dimensions of our galaxy? 10-20 billion years Milky Way 100,000 light years by 10,000 light years

28-4 Galaxies and the Universe 5. Types of Galaxies: Spiral Galaxies- Pinwheel in shape. b. Elliptical-Lens shaped with stars clustered around the center. c. Irregular-random arrangement of stars. d. Quasars-Extremely distant objects. Very luminous.  

28-4 Galaxies and the Universe 6. Origin of the Universe What does the Big Bang Model Say? b. Evidence support the model is the universe’s expansion. c. What other supporting evidence is there? The universe starting from a central microscopic point Redshifts