Table of Contents Chapter 15 Stars, Galaxies, and Universe Chapter Preview 15.1 Telescopes 15.2 Characteristics of Stars 15.3 Lives of Stars 15.4 Star Systems and Galaxies 15.5 The Expanding Universe

Chapter Preview Questions 1. What is light? a. electrical energy from the sun b. matter that travels as waves c. energy that travels in the form of waves d. matter that allows us to see things

Chapter Preview Questions 1. What is light? a. electrical energy from the sun b. matter that travels as waves c. energy that travels in the form of waves d. matter that allows us to see things

Chapter Preview Questions 2. As the result of nuclear fusion, the sun gives off a. mechanical and electrical energy. b. chemical energy and sound. c. electrical energy and light. d. heat and light.

Chapter Preview Questions 2. As the result of nuclear fusion, the sun gives off a. mechanical and electrical energy. b. chemical energy and sound. c. electrical energy and light. d. heat and light.

Chapter Preview Questions 3. How many stars are in our solar system? a. one b. hundreds c. thousands d. millions

Chapter Preview Questions 3. How many stars are in our solar system? a. one b. hundreds c. thousands d. millions

Chapter Preview Questions 4. The planets and moons in our solar system are visible because they a. emit their own light. b. undergo nuclear fusion. c. absorb light from the sun. d. reflect light from the sun.

Chapter Preview Questions 4. The planets and moons in our solar system are visible because they a. emit their own light. b. undergo nuclear fusion. c. absorb light from the sun. d. reflect light from the sun.

What is the structure and composition of the universe? Suppose you shine the beam of a flashlight against the wall of a darkened room. You then measure the size of the circle made by the beam on the room. What do you think would happen to the size of the circle if you moved closer to the wall? Farther from the wall? Explain your answer.

End of Chapter Preview

Section 1: Telescopes What are the regions of the electromagnetic spectrum? What are telescopes and how do they work? Where are most large telescopes located?

Electromagnetic Radiation Visible light (Optical) Energy that travels through space in the form of waves All colors that can be seen Roy G. Biv – colors in the rainbow, through a prism Red, orange, yellow, green, blue, indigo, violet.

Electromagnetic spectrum Types of radiation Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays

Electromagnetic Radiation The electromagnetic spectrum includes the entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

Types of Telescopes A refracting telescope uses convex lenses to focus light. A reflecting telescope has a curved mirror in place of an objective lens.

Four Views of the Crab Nebula Different type of telescopes collect electromagnetic radiation at different wavelengths. Astronomers are able to learn a great deal about the Crab Nebula by examining these different images. The images are shown at different scales.

Types of Telescopes Type of Radiation Name and location of telescope What has been found? Radio waves , Infrared Microwave X-Ray Visible

Ultraviolet GALEX, space Gamma

Click the SciLinks button for links on telescopes.

Click the Video button to watch a movie about telescopes.

The Hubble Space Telescope Click the Video button to watch a movie about the Hubble Space Telescope.

End of Section: Telescopes

Section 2: Characteristics of Stars How are stars classified? How do astronomers measure distances to the stars? What is an H-R diagram and how do astronomers use it?

Classifying Stars Constellation Stars Imaginary pattern of stars Made up mostly of H (hydrogen) Produce energy through nuclear fusion Color shows temperature red – cool stars (3200°C) yellow – hotter stars (5500°C) blue – hottest stars (20,000°C)

Size of Stars Giant or supergiant Medium size Small size Very large stars Our sun’s size White dwarf – size of Earth Neutron stars – 20 km diameter.

Star Size Stars vary greatly in size. Giant stars are typically 10 to 100 times larger than the sun and more than 1,000 times the size of a white dwarf.

Chemical Composition Spectrograph 73% hydrogen (H) 25% helium (He) 2% other elements Breaks light into different colors Can determine gases in stars.

Star Spectrums Astronomers can use line spectrums to identify the chemical elements in a star. Each element produces a characteristic pattern of spectral lines.

Brightness of Stars Amount of light given off Depends on size and temperature Betelgeuse – cool and large, shines brightly Rigel – hot, brighter than Betelgeuse though smaller Brightness as seen from Earth Comparative. Apparent Brightness

Brightness of Stars Absolute Brightness No matter where you measure the brightness, it has the same measurement Can compare brightness of all stars to each other.

Measuring Distances to Stars Astronomical Unit Light year 1 A.U. is the distance between Earth and the sun 1.44 X 108 kilometers (km). Measure distances between stars Distance light travels in one year 9.5 X 1012 kilometers (km).

The Hertzsprung-Russell Diagram Astronomers use H-R diagrams to classify stars and to understand how stars change over time. Compare 2 stars – color, brightness, temp.

H-R Diagram On the H-R diagram: Bottom X axis shows temperature, hottest on left, coolest on right Top X axis shows color of stars, blue on left, red on right Y axis shows brightness increasing

Summary of Section Use the following as a guide to write a summary of this section: Stars are classified by ___________, _________, _______, ________, __________. Some stars appear brighter than others because ___________. Light years are used to measure distances between stars because ___________. The H-R diagram is used to _________.

Click the PHSchool.com button for an activity about types of stars. More on Types of Stars Click the PHSchool.com button for an activity about types of stars.

End of Section: Characteristics of Stars

Section 3: Lives of Stars How does a star form? What determines how long a star will exist? What happens to a star when it runs out of fuel?

A Star Is Born Nebula – large cloud of gas & dust, large volume Gravity pulls gas & dust together Forms protostar (no nuclear fusion) When gas & dust are very dense & hot, nuclear fusion starts, a star is born Stars with more mass use up fuel faster than smaller stars Small stars – 200 billion years Medium stars – 10 billion years (our sun) Large stars – 10 million years

The Lives of Stars A star’s life history depends on its mass. After a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole.

The Lives of Stars A star’s life history depends on its mass. After a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole.

Deaths of Stars Hydrogen fuses to become helium and releases a lot of energy When star uses up hydrogen helium can start fusing and creating new elements Helium fuses in core to become carbon, oxygen Massive stars produce heavier elements like iron Stars without fuel become white dwarf, neutron star or black hole Low mass star red giant planetary nebula white dwarf black dwarf

Deaths of Stars Supernova – explosion of supergiant Explosion creates heavy elements, lead, gold Explosion creates new stars with material from old star (recycling!) Neutron star – remains of supergiant Smaller, denser than white dwarfs Pulsar – spinning neutron star Gives off pulses of radiation in the form of radio waves Black hole – gravity so strong nothing can escape Cannot be detected directly

The Lives of Stars Activity Click the Active Art button to open a browser window and access Active Art about the lives of stars.

Pulsar Pulsars are spinning neutron stars that emit steady beams of radiation.

Black Holes The remains of the most massive stars collapse into black holes. Here, a black hole is shown pulling matter from a companion star. Gas near a black hole pulled inward, x-rays observed, gravitational effect on nearby stars

End of Section: Lives of Stars

Section 4: Star Systems and Galaxies What is a star system? What are the major types of galaxies? How do astronomers describe the scale of the universe?

Star Systems and Clusters Our galaxy = Milky Way Star systems – two or more stars together Binary stars – two stars or double stars One star brighter, more massive Dimmer star’s gravity causes “wobble” Eclipsing binary – one star blocks light from another star Triple stars – 3 stars together Found at least 500 other planets that revolve around stars- called exoplanets. Found by “wobble” of star.

Star Clusters Large groupings of stars Formed from same nebula at about same time Open clusters – disorganized appearance, a few thousand stars Globular clusters – large groupings of older stars, more than a million stars.

Galaxies Huge group of single stars, star systems, star clusters, dust and gas Many have black holes in center Billions of stars in galaxy Billions of galaxies in universe Quasar – distant, very bright young galaxy with black hole in center.

Types of Galaxies Astronomers classify most galaxies into three main categories: spiral, elliptical, and irregular.

Types of Galaxies Spiral – bulge in middle, arms spiral outward Spiral arms contain new stars, gas, dust New stars formed in spiral arms Elliptical – round or oval shape, billions of stars, little gas or dust, therefore old stars Irregular – smaller than other galaxies Young stars, lots of gas and dust Located close to larger galaxies.

Structure of the Milky Way Our solar system is located in a spiral galaxy called the Milky Way. From the side, the Milky Way appears to be a narrow disk with a bulge in the middle. The galaxy’s spiral structure is visible only from above or below. Center is 25,000 light years away from Earth

Scale of the Universe Universe Scientific Notation All of space and everything in it Objects are very large and very far away Uses powers of ten to write very large or very small numbers One light year = 9,500,000,000,000,000 meters. Written as 9.5 X 1015m, 9.5X1012 km.

Scientific Notation The bright star Deneb is about 3,230 light-years from Earth. To express this number in scientific notation, first insert a decimal point in the original number so that you have a number between one and ten. In this case, the number is 3.23. To determine the power of 10, count the number of places that the decimal point moved. Here the decimal point moved three places. 3,230 light-years = 3.23 x 103 light-years.

Click the SciLinks button for links on galaxies.

End of Section: Star Systems and Galaxies ALL CLASSES: Draw a triple Venn Diagram of the 3 types of galaxies. Answer questions 1a,b,c, 2a,b,c, 3a,b,c, and 4 on P. 621. End of Section: Star Systems and Galaxies

Section 5: The Expanding Universe What is the big bang theory? How did the solar system form? What do astronomers predict about the future of the universe?

Retreating Galaxies All of the distant galaxies astronomers have observed are moving rapidly away from our galaxy and from each other.

Speeding Galaxies Use the graph to answer the questions about moving clusters of galaxies.

Speeding Galaxies Reading Graphs: How far away is the Bootes cluster? How fast is it moving? About 2.5 billion light-years; about 39,000 km/sec

Speeding Galaxies Reading Graphs: Which galaxy is moving away the fastest? Which galaxy is closest to Earth? Hydra; Virgo

Speeding Galaxies Drawing Conclusions: How are the distance and speed of a galaxy related? The greater the distance from Earth, the greater the speed of the galaxy.

Speeding Galaxies Predicting: Predict the speed of a galaxy that is 5 billion light-years from Earth. Its speed would be about 80,000 km/s.

Moving Galaxies The galaxies in the universe are like the raisins in rising bread dough.

Formation of the Solar System The solar system formed from a collapsing cloud of gas and dust.

Links on the Expanding Universe Click the SciLinks button for links on the expanding universe.

End of Section: The Expanding Universe

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