1. Stars, Galaxies, and the Universe Telescopes Characteristics of Stars Lives of Stars Star Systems and Galaxies The Expanding Universe Table of Contents

2. Stars, Galaxies, and the Universe Electromagnetic Radiation Electromagnetic radiation – energy that can travel through space in the form of waves. –Comes in many forms: visible light, infrared, x-rays, gamma rays, etc. Wavelength – distance between the crest of one wave and the crest of the next wave.

3. Stars, Galaxies, and the Universe Electromagnetic Radiation Electromagnetic spectrum – consists of all the different types of electromagnetic waves –Includes: radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. - Telescopes

4. Stars, Galaxies, and the Universe Types of Telescopes Telescopes – instruments that focus light and other forms of electromagnetic radiation. –Make distant objects appear larger and brighter –Optical telescope – uses lenses or mirrors to collect and focus visible light. –Refracting telescope – uses convex lenses to gather and focus light. Convex lens – transparent glass curved so that the middle is thicker than the edges.

5. Stars, Galaxies, and the Universe Types of Telescopes Reflecting telescope – uses a curved mirror to collect and focus light – The largest optical telescopes used today Radio telescope – used to detect radio waves from objects in space. –Many other telescopes that can detect different wave lengths

6. Stars, Galaxies, and the Universe A refracting telescope uses convex lenses to focus light. A reflecting telescope has a curved mirror in place of an objective lens.

7. Stars, Galaxies, and the Universe Telescopes Click the Video button to watch a movie about telescopes. - Telescopes

8. Stars, Galaxies, and the Universe Observatories Observatory – a building that contains one or more telescopes. –Many large observatories are located on mountaintops or in space. Advanced telescopes are equipped with computer systems that correct images for problems Some telescopes are placed in space to detect X-rays, gamma rays, and most ultraviolet radiation Palomar Observatory – San Diego, California

9. Stars, Galaxies, and the Universe Hubble Space Telescope – reflecting telescope with a mirror 2.4 meters in diameter. –Orbits the earth above the atmosphere –Produces very detailed images in visible light, ultraviolet, and infrared radiation.

10. Stars, Galaxies, and the Universe The Hubble Space Telescope Click the Video button to watch a movie about the Hubble Space Telescope. - Telescopes

11. Stars, Galaxies, and the Universe Graphic Organizer Telescopes On Earth Radio waves can be Visible light collect types of radiation Infrared In space only Ultraviolet Gamma rays collect types of radiation X-rays

12. Stars, Galaxies, and the Universe Classifying Stars Stars are giant balls of hydrogen gas –Radiate energy through nuclear fusion Characteristics used to classify stars include: color, temperature, size, composition, and brightness. 1) Color – a star’s color tells us what its temperature is. –Red = about 3,200°C –Yellow = about 5,800°C –Blue = about 20,000°C

13. Stars, Galaxies, and the Universe Classifying Stars 2) Size – stars vary in size –small, medium, large, and very large –The sun is a medium sized star –Betelgeuse is a supergiant star that would fill our solar system out to Jupiter. –White dwarfs – small stars about the same size as the earth –Neutrons – tiny stars only about 20 kilometers in diameter

14. Stars, Galaxies, and the Universe Star Size - Characteristics of Stars 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.

15. Stars, Galaxies, and the Universe Classifying Stars 3) Composition - Stars vary in their chemical composition. Most stars are made of about 73 % hydrogen, 25 % helium, and 2 % other elements by mass. –This is the composition of the sun as well

16. Stars, Galaxies, and the Universe Classifying Stars Spectrograph – device that breaks light into colors and produces an image of the resulting spectrum. The light from stars passes through a spectrograph on a telescope. Some wavelengths of light are absorbed and create a black line. Each element has it’s own set of lines on the spectrograph….like a finger print.

17. Stars, Galaxies, and the Universe Star Spectrums - Characteristics of Stars Astronomers use line spectrums to identify the chemical elements in a star. Each element produces a characteristic pattern of spectral lines.

18. Stars, Galaxies, and the Universe Classifying Stars 4) Brightness - The brightness of a star depends upon both its size and temperature. –Betelgeuse is fairly cool, so it does not give off a lot of light per square meter. But is very large, so it shines brightly. –Rigel is hotter, giving off more light per square meter. –Even though Rigel is smaller than Betelgeuse, it shines more brightly

19. Stars, Galaxies, and the Universe

20. Classifying Stars How bright a star looks from Earth depends on two factors: –Its distance from Earth –How bright the star truly is Apparent brightness – brightness of a star as seen from Earth. –Easy to measure with instruments on earth –But does not reflect how much light a star really gives off

21. Stars, Galaxies, and the Universe Classifying Stars Absolute brightness – brightness the star would have if it were at a standard distance from Earth –Astronomers can calculate a stars absolute brightness by using: –the star’s apparent brightness –its distance from Earth

22. Stars, Galaxies, and the Universe Measuring Distances to Stars Astronomers use a unit called the light-year to measure distances between the stars. Light-year – distance that light travels in one year (about 9.5 million kilometers) –NOTE: light-year measures distance not time!! –Sun is about 8 minutes away (about 0.0000152 light-years) –Proxima Centauri (the next closest star) is 4.2 light-years away

23. Stars, Galaxies, and the Universe Measuring Distances to Stars Astronomers often use parallax to measure distances to nearby stars. Parallax is the apparent change in position of an object when you look at it from different places.

24. Stars, Galaxies, and the Universe Measuring Distances to Stars Scientists look at a star in the sky then look at it again 6 months later (when the earth is on the other side of the sun) –They measure the distance the star has seemed to have moved against the backdrop then they are able to calculate the distance –Astronomers can use parallax to measure distances up to a few hundred light-years from Earth.

25. Stars, Galaxies, and the Universe Measuring Distances to Stars - Characteristics of Stars Astronomers often use parallax to measure distances to nearby stars.

26. Stars, Galaxies, and the Universe The Hertzsprung-Russell Diagram Hertzsprung-Russell diagram – graph relating the surface temperatures and absolute brightnesses of stars. –Surface temperatures of stars are plotted on the x-axis and their absolute brightness on the y-axis. –Main sequence – diagonal area on an H-R diagram that includes more than 90 percent of all stars.

27. Stars, Galaxies, and the Universe The Hertzsprung-Russell Diagram - Characteristics of Stars Astronomers use H-R diagrams to classify stars and to understand how stars change over time.

28. Stars, Galaxies, and the Universe More on Types of Stars Click the PHSchool.com button for an activity about types of stars. - Characteristics of Stars

29. Stars, Galaxies, and the Universe The Lives of Stars Just like most things, stars go through a “life” cycle – born, grow, and die –Note: stars are not really alive!! Nebula – a large cloud of gas and dust spread out in an immense volume. –As gravity pulls the gas and dust of the nebula together it forms a protostar. A star is born when the contracting gas and dust from a nebula become so dense and hot that nuclear fusion starts

30. Stars, Galaxies, and the Universe The Lives of Stars How long a star lives depends on its mass. –The smaller the mass, the longer the life (Like cars burning fuel) –Small stars tend to live about 200 billion years –Medium stars tend to live about 10 billion years. Our sun is a medium star and is believed to have formed about 4.6 billion years ago. –Large stars tend to live only about 10 million years.

31. Stars, Galaxies, and the Universe The Death of Stars After a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole Toward the end of their lives: –Small and medium stars grow large, expanding their gas outward until they become a red giant. –After that they lose most of their outer gases until a blue-white hot core is left called a white dwarf.

32. Stars, Galaxies, and the Universe The Death of Stars –White dwarfs no longer have fuel but they continue glowing. When they stop glowing they are called black dwarfs. –A large star will grow larger much more rapidly, turning into a supergiant. –When the supergiant runs out of fuel it will explode suddenly into a supernova.

33. Stars, Galaxies, and the Universe The Death of Stars Sometimes when a supergiant explodes it will leave a small dense core called a neutron star. –Neutron stars are even smaller and denser than white dwarfs. –Pulsars – neutron stars spin rapidly sending off waves of energy

34. Stars, Galaxies, and the Universe Your turn!! Can you remember the types of stars?? Lets try…. Star Vocabulary – Matching Activity

35. Stars, Galaxies, and the Universe - 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.

36. Stars, Galaxies, and the Universe Your turn!! Can you remember the types of stars?? Lets try…. Star Puzzle Flipchart

37. Stars, Galaxies, and the Universe The Death of Stars Black hole – object whose gravity is so strong that nothing, not even light, can escape. –Occur when a very massive star explodes in a supernova. –A huge amount of mass is left behind (5 times the mass of our sun) creating a huge gravitational force. –Eventually, the matter is pulled in so tightly that not even light or any other kind of electromagnetic wave can escape.

38. Stars, Galaxies, and the Universe Black Holes - Lives of Stars How do scientists detect black holes? –To find the answer read about black holes on page 147 of your books.

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

40. Stars, Galaxies, and the Universe Star Systems and Clusters Most stars are members of groups of two or more stars, called star systems. Binary stars (double stars) – star systems that have two stars –Often one star in a binary star is much brighter and more massive than the other. –When the second star is too dim to see, scientists look at the wobbling motion of the bright star to detect the second star.

41. Stars, Galaxies, and the Universe Star Systems and Clusters Eclipsing binary – binary star system in which one star periodically blocks the light from the other. Many stars belong to larger groupings called star clusters –Open cluster – has a loose, disorganized appearance and contains no more than a few thousand stars. –Globular cluster – a large, round, densely-packed grouping of older stars.

42. Stars, Galaxies, and the Universe Galaxies Galaxy – a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity. Astronomers classify most galaxies into spiral, elliptical, and irregular. –Spiral galaxies – have a bulge in the middle and arms that spiral outward, like pinwheels

43. Stars, Galaxies, and the Universe Galaxies –Elliptical galaxy – shaped like a round or flattened ball, generally containing only old stars. –Irregular galaxy – does not have a regular shape. Quasar – an enormously bright, distant galaxy with a giant black hole at its center.

44. Stars, Galaxies, and the Universe Structure of the Milky Way - Star Systems and Galaxies 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.

45. Stars, Galaxies, and the Universe 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 10 3 light-years - Star Systems and Galaxies

46. Stars, Galaxies, and the Universe Scientific Notation Practice Problem The sun takes about 220,000,000 years to revolve once around the center of the galaxy. Express this length of time in scientific notation. 2.2 X 10 8 years - Star Systems and Galaxies

47. Stars, Galaxies, and the Universe How the Universe Formed Big bang theory – scientists believe was the initial explosion that resulted in the formation and expansion of the universe. –According to this theory, the universe formed in an instant, billions of years ago, in an enormous explosion Hubble’s law – states that the farther away a galaxy is, the faster it is moving away from us –This law strongly supports the big bang theory

48. Stars, Galaxies, and the Universe Retreating Galaxies - The Expanding Universe All distant galaxies are moving rapidly away from our galaxy and from each other.

49. Stars, Galaxies, and the Universe Speeding Galaxies Use the graph to answer the questions about moving clusters of galaxies. - The Expanding Universe

50. Stars, Galaxies, and the Universe Speeding Galaxies –About 2.5 billion light- years; about 39,000 km/sec Reading Graphs: –How far away is the Bootes cluster? How fast is it moving? - The Expanding Universe

51. Stars, Galaxies, and the Universe Speeding Galaxies –Hydra; Virgo Reading Graphs: –Which galaxy is moving away the fastest? Which galaxy is closest to Earth? - The Expanding Universe

52. Stars, Galaxies, and the Universe Speeding Galaxies –The greater the distance from Earth, the greater the speed of the galaxy. Drawing Conclusions: –How are the distance and speed of a galaxy related? - The Expanding Universe

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

54. Stars, Galaxies, and the Universe Moving Galaxies - The Expanding Universe The galaxies in the universe are like the raisins in rising bread dough.

55. Stars, Galaxies, and the Universe Formation of the Solar System About five billion years ago, a giant cloud of gas and dust collapsed to form our solar system. The solar system was formed in stages: –1) Solar Nebula – large cloud of gas and dust Gravity eventually pulled the gas and dust together forming planetesimals –2) Planetesimal – small asteroid-like bodies that formed the building blocks of the planets. Eventually these formed the more solid objects we call planets.

56. Stars, Galaxies, and the Universe Formation of the Solar System - The Expanding Universe The solar system formed from a collapsing cloud of gas and dust.

57. Stars, Galaxies, and the Universe Formation of the Solar System Because the intense heat and solar winds blew light elements and gases away, the first four planets are small and rocky. Early solar winds could not reach the outer planets, so they remain large and consist of lighter elements.

58. Stars, Galaxies, and the Universe What is the future of the universe? Two major theories: –Continue to expand, eventually burning out –Gravity will eventually pull galaxies back together (“reverse big bang”) Which theory is correct?? –Read page 152 in your books to find the answer.