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Cullman Hall of the Universe Investigate Stars and Galaxies OVERVIEW Students will investigate stars and galaxies, how they form, how their lives play out based on their composition and mass, and how they die. BACKGROUND FOR EDUCATOR A star’s life cycle depends almost entirely on its mass. Higher-mass stars burn hotter, brighter, and faster than lower-mass stars, and die more violently. Galaxies have different shapes, depending on the orbits of the objects they contain. Sometimes galaxies collide, changing their shapes. BEFORE YOUR VISIT Students will be introduced to the life cycle of stars — how they form, live, and die. Quiz: The Lives of Stars amnh.org/ology/features/whatdoyouknow_stars/ Have students pair up for the quiz. Have the pairs share the answers in a class discussion, but do not supply the answers. (See the “Back in the Classroom” section for related activity.) Interferometry: Sizing up the stars sciencebulletins.amnh.org/?sid=a.f.interferometry.20060801 Have students watch this video about a revolutionary set of star-imaging telescopes. Use the related educator resources (amnh.org/sciencebulletins/ content/a.f.interferometry.20060801/related/edres.html) to lead a class discussion. DURING YOUR VISIT Cullman Hall of the Universe Lower Level (40 minutes) Using their student worksheets, have students visit the following two locations to collect evidence about stars. They can explore individually, in pairs, or in small groups. Activities for Grades 9-12 NYS Earth Science Core Curriculum: PS 1.2b: Stars form when gravity causes clouds of molecules to contract until nuclear fusion of light elements into heavier ones occurs. Fusion releases great amounts of energy over millions of years. •T he stars differ from each other in size, temperature, and age •O ur Sun is a medium-sized star within a spiral galaxy of stars known as the Milky Way. Our galaxy contains billions of stars, and the universe contains billions of such galaxies. Plan how your students will explore the Cullman Hall of the Universe the student worksheets. You many wish to have them work individually or in pairs. Distribute the corresponding worksheets to the expert groups. You may want to review the worksheets and the map of the exhibition with students to make sure they understand what they are to do. • “ Formation & Evolution of Stars” panel: Starting at the left-hand side (yellow letters), students will examine the comparative timeline and stages of the evolution of different mass stars. • “ Galaxies” and “Milky Way & Its Neighbors” panels: In the Galaxies section (blue letters), students will explore animations, images, and text to learn how galaxies interact. Scales of the Universe 2nd Floor (20 minutes) Use the Stellar Scale section of the Teaching in the Exhibition section to explore the Scales of the Universe with your students. © 2012 American Museum of Natural History. All rights reserved. amnh.org/education/universe Cullman Hall of the Universe Activities for Grades 9-12 BACK IN THE CLASSROOM Discussion: Stars As a group, compare the worksheets and discuss the way students interpreted the data they recorded in the two charts. Ask: What patterns did they notice? (Answers will vary but may include: The temperature of a star determines its color; in the Main Sequence stars, hotter stars are brighter; the larger a star’s mass to begin with, the shorter its life.) Activity: Exploring Brown Dwarfs Have students watch the Science Bulletins video “Brown Dwarfs: Tail End of the Stars” (sciencebulletins.amnh.org/ ?sid=a.f.brown_dwarfs.20110606) to learn what happens when there isn’t quite enough mass to make a low-mass star. Allow students to take notes during the video. Then ask the following questions. (You may want them to watch the video a second time.) •W hy don’t brown dwarfs shine? (Answer: They don’t have enough mass to produce the temperatures and densities in their core that lead to nuclear fusion. Nuclear fusion causes stars to shine.) •H ow does astronomer Quinn Konopacky study brown dwarfs? (Answer: Earth’s atmosphere is turbulent and distorts light coming from space. The Adaptive Optics System measures that turbulence and sends that information to a deformable mirror, which compensates for the distortion and obtains a sharp image.) •H ow can Quinn determine the mass of a brown dwarf? (Answer: How quickly or how slowly an object orbits another object depends on how massive it is. Quinn determines a brown dwarf’s mass by measuring the speed of its orbit.) •T heorists measure an object’s heat, brightness, and age and enter this data into computer models in order to predict its mass. Often the data Quinn collects does not match up with their predictions. How does this help theorists? (Answer: Theorists enter the new data to make their models more accurate.) Actvity/Discussion: The Lives of Stars Have students retake the Ology quiz that they took before their Museum visit. Give out the answers and have them compare their pre- and post-visit scores. Ask: Did their scores improve? Are there questions they could research further? (Answers will vary.) © 2012 American Museum of Natural History. All rights reserved. amnh.org/education/universe Cullman Hall of the Universe Grades 9-12 Student Worksheet: Investigate Stars Go to the “STARS” wall (in yellow letters). 1. Read the panel: “Formation and Evolution of Stars”. What universal force causes star formation? 2. Look at the wall panels illustrating the “Lives of Stars” and describe different-mass stars at the different stages of their development in the appropriate box: STAR TYPE BIRTH LIFE OLD AGE DEATH REMNANT Low-mass star x Sun’s mass: Age at death: IntermediateMass Star x Sun’s mass: Age at death: High-mass star x Sun’s mass: Age at death: Very High-mass star Age at death: Comparing the information in the “Star Type” column, what can you say about the relationship between a star’s mass and its lifespan? © 2012 American Museum of Natural History. All rights reserved. amnh.org/education/universe Cullman Hall of the Universe Grades 9-12 3. Look at the “Organizing the Stars” panel. The HR diagram shows stars organized according to their luminosity (brightness) and temperature. Using the information in the diagram and also in the sections on star type you used in the chart above, record the following information about each star: STAR NAME LUMINOSITY (relative to the sun) TEMPERATURE STAR TYPE/COLOR Spica Sirius Polaris The Sun Sirius B Barnard’s star How do star temperature and luminosity relate to the star type and color? Go to the “GALAXY” wall (in blue letters). 4. Look at the “Formation of a Galaxy” panel and Galaxy wall. Read about what a galaxy is and the different types that have been observed. What holds stars in galaxies? Why are galaxies different shapes? 5. Read the panel on the Milky Way and its neighbors, and look at the animation on the floor of the colliding galaxies. Describe how galaxies interact and why: © 2012 American Museum of Natural History. All rights reserved. amnh.org/education/universe Cullman Hall of the Universe Grades 9-12 Student Worksheet: Investigate Stars ANSWER KEY Go to the “STARS” wall (in yellow letters). 1. Read the panel: “Formation and Evolution of Stars”. What universal force causes star formation? (Answer: gravity) 2. Look at the wall panels illustrating the “Lives of Stars” and describe different-mass stars at the different stages of their development in the appropriate box: STAR TYPE BIRTH LIFE Low-mass star x Sun’s mass: (8-80%) (Born in a cluster with other stars, a gravitational collapse of material initiates a nuclear fusion reaction.) (The low rate of nuclear fusion could last for trillions of years — longer than the current age of the universe!) (Born in a cluster with other stars, a gravitational collapse of material initiates a nuclear fusion reaction.) Age at death: (1 trillion years) IntermediateMass Star x Sun’s mass: (.8-8) Age at death: (10 billion years) High-mass star x Sun’s mass: (8-20) Age at death: (10 million years) Very High-mass star (20-100) Age at death: (1 million years) DEATH REMNANT X (At the end of its life, a low-mass star transitions into a red giant.) (After shedding most of its mass during the red giant phase, a white dwarf star remains.) (During most of its life, a star fuses hydrogen and helium in its core.) (Towards the end of its life, an intermediatemass star transitions into a red giant.) (After the star exhausts its fuel, its atmosphere is blown off, creating a planetary nebula.) (The hot core of the star is left behind as a white dwarf.) (Born in a cluster with other stars, a gravitational collapse of material initiates a nuclear fusion reaction.) (Because of the (When the nuclear fusion in the core progresses through heavier elements, the star expands into a supergiant.) (A high mass star dies in a supernova explosion, expelling about 90% of its mass.) (The collapsed material remaining after the supernova forms an extremely dense object called a neutron star.) (Born in a cluster with other stars, a gravitational collapse of material initiates a nuclear fusion reaction. A star cannot form at more than 100x the mass of the Sun.) (The fuel in a very high-mass star is exhausted quickly.) (A very high mass star becomes a very large and luminous supergiant at the end of its life.) (Death usually comes in the form of a supernova explosion, as in the case of the high-mass star.) (The collapse of a very high-mass star results in a black hole, which warps the fabric of space so much that light cannot escape, and therefore it cannot be seen directly.) high rate of energy that is produced by nuclear fusion in a high-mass star, its fuel burns quickly.) OLD AGE Comparing the information in the “Star Type” column, what can you say about the relationship between a star’s mass and its lifespan? (Answer: The larger mass a star begins with, the shorter its lifespan will be.) © 2012 American Museum of Natural History. All rights reserved. amnh.org/education/universe Cullman Hall of the Universe Grades 9-12 ANSWER KEY 3. Look at the “Organizing the Stars” panel. The HR diagram shows stars organized according to their luminosity (brightness) and temperature. Using the information in the diagram and also in the sections on star type you used in the chart in Step 2, record the following information about each star: (Teacher’s Note: Because the HR diagram only designates some temperatures and luminosities on the axes, all student readings from the chart will be very approximate. You may supplement this activity using the Earth Science Regents resource table called “Characteristics of Stars”.) STAR NAME LUMINOSITY (relative to the sun) TEMPERATURE STAR TYPE/COLOR Spica ~10 3 35,000°C main sequence/blue Sirius ~75 10,000°C main sequence/blue Polaris ~10 4 6,000°C Giant star/yellow-white The Sun 1 5,000°C Main sequence/yellow Sirius B ~.001 8,000°C White dwarf Barnard’s star ~10 -5 3,000°C Main sequence /red How do star temperature and luminosity relate to the star type and color? (Answer: The temperature of a star determines its color; in the Main Sequence stars, higher temperature correlates also correlates to higher luminosity.) Go to the “GALAXY” wall (in blue letters). 4. Look at the “Formation of a Galaxy” panel and Galaxy wall. Read about what a galaxy is and the different types that have been observed. (Answer: gravity) What holds stars in galaxies? Why are galaxies different shapes? (Answer: The initial orbits and collective rotation of stars and other material in a galaxy determines its shape. These are determined by its formation, e.g. from a disk of gas, from a collision of two galaxies.) 5. Read the panel on the Milky Way and its neighbors, and look at the animation on the floor of the colliding galaxies. Describe how galaxies interact and why: (Answer: The proximity of the two disk or spiral galaxies allows their gravity to distort each other. If they become close enough they may even combine, creating a larger and elliptically-shaped galaxy.) © 2012 American Museum of Natural History. All rights reserved. amnh.org/education/universe