Stars, Galaxies, and the Universe

Stars, Galaxies, and the Universe Preview • Multiple Choice • Short Response • Reading Skills • Interpreting Graphics

Multiple Choice 1. What accounts for different stars being seen in the sky during different seasons of the year? A. stellar motion around Polaris B. Earth’s rotation on its axis C. Earth’s revolution around the sun D. position north or south of the equator

Multiple Choice, continued 2. How do stellar spectra provide evidence that stars are actually moving? F. Dark-line spectra reveal a star’s composition. G. Long-exposure photos show curved trails. H. Light separates into different wavelengths. I. Doppler shifts occur in the star’s spectrum.

Multiple Choice, continued 3. What happens to main-sequence stars like the sun when energy from fusion is no longer available? A. They expand and become supergiants. B. They collapse and become white dwarfs. C. They switch to fission reactions. D. They contract and turn into neutron stars.

Multiple Choice, continued 4. Which type of star is most likely to be found on the main sequence? F. a white dwarf G. a red supergiant H. a yellow star I. a neutron star

Multiple Choice, continued 5. Evidence for the big bang theory is provided by A. cosmic background radiation. B. apparent parallax shifts. C. differences in stellar luminosity. D. star patterns called constellations.

Short Response 6. What type of galaxy has no identifiable shape? irregular galaxy

Short Response, continued • What is the collective name for the Milky Way galaxy and a cluster of approximately 30 other galaxies located nearby? the local group

Short Response, continued 8. What is the name for stars that seem to circle around Polaris and never dip below the horizon? circumpolar stars

Reading Skills Read the passage below. Then, answer questions 9–11. Geomagnetic Poles Today, we know that Copernicus was right: the stars are very far from Earth. In fact, stars are so distant that a new unit of length—the light-year—was created to measure their distance. A light-year is a unit of length equal to the distance that light travels through space in 1 year. Because the speed of light through space is about 300,000 km/ s, light travels approximately 9.46 trillion kilometers in one year. Even after astronomers figured out that stars were far from Earth, the nature of the universe was hard to understand. Some astronomers thought that our galaxy, the Milky way, included every object in space. In the early 1920’s Edwin Hubble made one of the most important discoveries in astronomy. He discovered that the Andromeda galaxy, which is the closest major galaxy to our own, was past the edge of the Milky Way. This fact confirmed the belief of many astronomers that the universe is larger than our galaxy.

Reading Skills, continued 9. Why was Edwin Hubble’s discovery important? A. Hubble’s discovery showed scientists that the universe was smaller than previously thought. B. Hubble showed that the Andromeda galaxy was larger than the Milky Way galaxy. C. Hubble's discovery showed scientists that the universe was larger than our own galaxy. D. Hubble showed that all of the stars exist in two galaxies, the Andromeda and the Milky Way.

Reading Skills, continued • Because the sun and Earth are close together, the distance between the sun and Earth is measured in light-minutes. A light-minute is the distance light travels in 1 minute. The sun is about 8 light-minutes from Earth. What is the approximate distance between the sun and Earth? F. 2,400,000 km G. 18,000,000 km H. 144,000,000 km I . 1,000,000,000 km

Reading Skills, continued 11. Why might scientists use light-years as a measurement of distance between stars? Light-years can express vast distances in compact form. When expressing distance between stars, using light-years is easier and more efficient than using kilometers.

Interpreting Graphics The diagram below shows a group of stars called the Big Dipper moving over a period of 200,000 years. Use this diagram to answer question 12.

Interpreting Graphics, continued 12. What does this series of drawings demonstrate about the individual stars in such a star group? Your answer should include the following: The diagrams show that the individual stars move at different rates and in different directions from one another; constellations are arbitrary human distinctions; the stars within constellations move along individual paths, not as a group; the familiar patterns that stars form in the Earth’s sky change slowly over time as the stars that comprise the patterns move relative to each other; star movement may take thousands of years to become apparent.

Multiple Choice, continued The table below shows data about several well-known stars. Distance is given in light-years. Use this table to answer questions 13 through 15.

Multiple Choice, continued 13. Which star has the brightest apparent magnitude as seen from Earth? F. Rigel G. Betelgeuse H. Mintaka I. Sirius

Multiple Choice, continued 14. Which of these stars is the coolest? A. Arcturus B. Betelgeuse C. Mintaka D. Vega

Multiple Choice, continued 15. Which star most likely has a temperature that is similar to the temperature of our sun? Explain how you are able to determine this information. Your answer should include the following: The star in the table with the closest temperature to the sun is most likely Capella; a star’s temperature can be determined by its color. Stars that have similar colors share a common temperature range; Capella is a yellow star like the sun and thus it is the most likely to have a temperature similar to that of the sun

Stars, Galaxies, and the Universe