Unit 7 Review Guide: The Universe Light Year: Unit of distance used to measure the great vastness of space. Galaxy: Large group of stars, gas, and dust held together by gravity. Spiral Galaxy: Galaxy in the shape of a giant pinwheel, with spiral arms, central bulge and a halo. Elliptical Galaxy: Galaxy in the shape of a 3-D ellipse. Irregular Galaxy: Galaxies with no obvious structure. Milky Way: Our home galaxy. Big Bang: Sudden expansion of space, which is thought to have created our universe. H-R Diagram: Diagram that graphs all the stars visible from Earth based on their temperature and luminosity. Main Sequence Stars: Average stars. Nebula: Cloud of dust and gas, from which stars are born. Protostar: Nebula which is almost a star. White Dwarf: Core that remains when a medium mass star dies. Nuetron Stars: Core that remains when a heavy (1.4 3x s the mass of the sun) star dies. Black Holes: Core that remains when a heavy (3x s the mass of the sun) star dies. Parallax Shift: Apparent shift in a star s position due to our changing view from Earth. Magnitude: Another word for brightness Apparent Magnitude: How bright a star looks from Earth. Absolute Magnitude: Measurement of the brightness of a star.
Practice Problems: 1. The pictures show the same stars at different times. Which hypothesis is best supported by these data? A. The stars are moving toward one another. B. The three stars are moving very fast. C. One star is moving around another star. D. The biggest star is closest to Earth. 2. A star might be much brighter than it appears to be. This is called the star s absolute magnitude. The difference in apparent magnitude and absolute magnitude is due primarily to the star s A. Surface temperature B. Motion through the universe C. diameter D. distance from the earth 3. A student sees a very bright star in the sky and thinks it might be the planet Venus. Which observation would lend support to this conclusion? A. After a few minutes, its position is relative to the surrounding has changed significantly. B. After an hour, its position relative to the horizon has changed. C. After an hour, its brightness has faded significantly. D. After a month, its position relative to the surrounding stars has changed. 4. The pole star, Polaris, is nearly stationary and straight overhead when seen from the North Pole. When viewed from the Equator, it A. Is nearly stationary and on the horizon B. Is nearly stationary and directly overhead C. rises barely above the eastern horizon, and sets in the west D. rises straight up in the east< passes directly overhead, and descends straight down in the west
5. Parallax can be used to measure a star s A. Distance from Earth B. Atmospheric temperature C. Gravitational strength D. Surface composition 6. What is the position of the star above the horizon? A. 35 B. 40 C. 55 D. 60 7. Which of these elements does this star contain? A. Mercury B. Calcium C. Sodium D. Neon
8. In the late 1920s, Edwin Hubble and Milton Humason determined the distance to a number of galaxies and the velocity of those galaxies relative to the Earth. The graph shows the early results that were obtained. What approximate ratio did the scientists calculate between velocity and distance based on these early findings? A. 150 kilometers per second per one million light years B. 300 kilometers per second per one million light years C. 450 kilometers per second per one million light years D. 600 kilometers per second per one million light years 9. Which image below best represents our galaxy? A. B. C. D.
10. What element is the main component of most stars? A. Nitrogen B. Iron C. Hydrogen D. Oxygen 11. Why do stars appear to change position in the night? A. Earth rotates on its axis B. Earth revolves around the sun C. The stars are moving away from each other D. Stars are very far away from the solar system 12. In 1912, an astronomer at Arizona s Lowell Observatory noticed that the lines in the spectra of most galaxies shifted toward the red end of the spectrum. Another American astronomer, Edwin hubble, later interpreted this discovery as evidence that A. Galaxies were once part of one huge mega galaxy. B. An explosion will one day result from the pressure building as the galaxies expand. C. Galaxies are moving away from each other in a constantly expanding universe. D. The largest galaxies are slowly engulfing their smaller neighbors 13. A light year measures A. Brightness B. Distance C. Radiation D. Time
14. What is the first stage in the life cycle of a star? A. Black hole B. Dwarf star C. Main-sequence star D. Stellar nebula 15. Which of these facts is the best supporting evidence that the universe is expanding A. The stars very in chemical composition. B. The galaxies are moving away from each other. C. The galaxies can spin to form eddies. D. The universe is filled with galaxies of different size. 16. Which of the above evolutionary stages of a massive star is called a supernova? A. 1 B. 2 C. 3 D. 4