1. Bell Work: Name 3 things all Electromagnetic Waves have in common.

2. Chapter 21 Stars, Galaxies, and the Universe

3. Electromagnetic Radiation Energy that can travel through space The Electromagnetic Spectrum Ranks Electromagnetic Waves based on their _______. Visible Light – Electromagnetic Radiation you can see Electromagnetic Radiation you can see Spectrum of visible light  ROY G. BIV

4. Telescopes Instruments that collect and focus light and other forms of electromagnetic radiation Used to make distant objects appear larger & brighter First used to study space by Galileo 2 Main Types: OpticalNon-Optical

5. Optical vs Non-Optical Optical Telescopes Uses lenses or mirrors to collect & focus VISIBLE light 2 Types: Refracting Telescopes Reflection Telescopes Source of Radiation: Stars, Planets, Moons Uses: Study size, composition, and movement of stars and galaxies Non-Optical Telescopes Collect and focus different types of electromagnetic radiation 3 Types: Radio Telescopes Ultraviolet Telescopes Infrared Telescopes

6. Refracting Telescope Uses Convex lenses to gather and focus light Convex Lens –glass curved so that the middle is thicker than the edges Tw0 Convex Lenses – one at each end of long tube Large Lens- Gathers Light  larger = more light it can collect Smaller Lens- Magnifies the image

7. Reflecting Telescopes 1 st one built in 1668 by Isaac Newton Uses a curved mirror to collect and focus light Uses two lenses like the refracting Today, the largest optical telescopes are all reflecting telescopes

8. Radio Telescopes Used to Detect RADIO waves in space Curve, reflecting surfaces Concentrates faint radio waves from space onto small antennas Larger = more radio waves it can collect Source of Radiation Galactic Centers, Stars, Black Holes Uses: Find Black Holes Map Galactic Centers

9. Bell Work: What is the difference between an optical and non-optical telescope?

10. Ultraviolet Telescopes Source of Radiation: Distant stars, Clouds of dust and gas Uses: To map sources and analyze their composition Infrared Telescopes Source of Radiation: Stars, Galaxies Uses: To study planets around other stars This image of the Pinwheel Galaxy combines data in the infrared, visible, ultraviolet and x-rays from four of NASA’s space telescopes.

12. Development of Telescopes 1897 – Yerkes Telescope in Wisconsin Largest refracting telescope ever built  collects most light 1931 – Accidental discovery of Radio Waves by Karl Jansky 1963 – Arecibo- radio telescope built in natural bowl in ground 1980 – Very Large Array – set of 27 radio telescopes in New Mexico 1990 – Hubble Space Telescope – Reflecting telescope above Earth’s atmosphere; very detailed images in visible light 1992 - Compton 1999 – Chandra – X-ray telescope; very detailed 2003 – Spitzer – 0.86 meter in diameter infrared telescope

14. Observatory- Building that contains one or more telescopes Many located on Mountaintops or in Space. Why? Earth’s atmosphere makes objects in space look blurry Sky on mountaintops is clearer & not brightened by city lights Telescopes in Space- Most radiation is blocked by Earth’s atmosphere To detect these  Scientists have placed telescopes in space The Keck observatory domes atop Mauna Kea ‬

15. Constellations An imaginary pattern of stars in the sky. Different cultures gave different names to the constellations Used by astronomers to locate objects in the night sky

16. Characteristics of Stars Scientists classify stars based on their: Color & Temperature: Reveals the surface temperature Hottest stars  blue Coolest Stars  red Size: Vary greatly in size Larger than the sun  Giant or Supergiant stars Size of Earth  White dwarf stars Chemical Composition: Most is 73% Hydrogen, 25% Helium (Similar to sun) Spectrograph - determines the elements in stars Brightness: Depends on size, temperature, & distance from Earth Apparent Brightness vs. Absolute Brightness

17. Bell Work: Name the 4 things Scientists look at to classify a star.

18. Measuring the Distance to Stars Astronomers use light- year units to measure distances between the stars Astronomers use parallax to measure distance. Parallax – apparent change in position of an object when you lo0k at it from different places Parallax – apparent change in position of an object when you lo0k at it from different places

19. The Hertzsprung-Russell Diagram Graphs made by two Scientists, Hertzsprung and Russell Graphs of surface temperatures and absolute brightness of stars to see how they were related Main Sequence – Diagonal area on Hertzsprung- Russell location of more than 90 percent of stars, including the sun Surface temp increase AS absolute brightness increases  hot blue star on left  cooler red stars on right Brightest stars  top (Giant & Supergiant) Cooler, not as bright stars  bottom (white dwarfs

20. Images from the Hubble Space Telescope showing the life cycle of stars. Life Cycle of Stars A star is born when nuclear fusion starts. Stars are born IN a nebula - huge clouds of dust and gas  gravity pulls together enough gas and dust a protostar is formed Stars grow old and begin to run out of fuel  the core shrinks; outer layers expand, cool, and become less bright; it is now called a red giant or a super giant (depending on the initial mass of the star)  After running out of “fuel” it will become either a black dwarf, neutron star, or black hole

21. The Lifecycle of a star depends on its original Mass. How long can a star live? About 10 million to 200 billion years White Dwarf Blue-white core of a star left behind and cools No fuel left but faintly glows Black Dwarf A White dwarf that no longer “glows”Supernova Explosion of a dying HIGH mass star Neutron stars Small, dense remains of a high mass star after a supernova Black holes Object with gravity so strong that nothing, even light, can escape Formed when the most massive stars collapse and die

22. Star Systems & Clusters Most stars are members of groups of two or more stars  star systems Binary stars  star systems with two stars Eclipsing binaries  star system in which one star periodically blocks the light from another; one may also appear dimmer from time to time Star Clusters  larger groupings stars belong to All stars in a cluster formed from the SAME nebula at about the SAME time and are about the SAME distance from Earth Open cluster  loose, disorganized, only a few thousand stars Globular cluster  large groupings of older stars

23. Galaxies – huge group of single stars, star systems, star clusters, dust and gas held together by gravity 3 main categories: 1. Spiral – bulge in middle with spiral arms; “pinwheel” Arms contain young stars, dust, & gas 2. Elliptical – round or flattened balls mainly old stars due to little, or almost no, gas or dust 3. Irregular- No regular shape Typically smaller Many bright, young stars

24. The Milky Way - A spiral galaxy where our solar system is located

25. The Universe: collectively describe the planets, stars, galaxies, and any other matter that exists in space The part of the universe that can be observed is believed to be 46 billion light years across and is expanding constantly. The part of the universe that can be observed is believed to be 46 billion light years across and is expanding constantly. How did the Universe form? Astronomers believe that our universe formed in an instant, enormous explosion billions of years ago – The Big Bang Theory Hubble’s Law – states that the farther away a galaxy is, the faster it is moving away from us Supports the Big Bang theory

26. What is the Future of the Universe ? Many Theories: 1. Continue to expand until stars run out of fuel  universe becomes cold and dark 2. gravity will begin to pull galaxies back together 