Full Name _____________________________________________ Date --12/08/14-- Student ID ____________ TA Name ___________________________________________Section ______ [8 PAGES - 44 QUESTIONS] 1. Here is a series of moon phases, top row, starting with the new moon on November 22, a full moon on December 6, and a new moon on December 22. What does today’s moon phase look like? Choose among those phases labeled “A, B, C, D, or E” – all are labeled December 8, but only 1 is correct. Figure 1. Phases of the Moon from November 22 to December 22, 2014 The phases of the moon progress smoothly. “C” is the correct answer, and if you examine the full moon just above, you will see that “C” is not a perfect circle. Besides, it is just 2 days past the full moon. “B” cannot be right because there are 6 days between the 8th and the 14th when there is a 3rd quarter moon – and the moon takes about 7 days between full and 3rd quarter. 2. No matter where you live on Earth, there is a location that has the same latitude but is 180° away in longitude (on the opposite side of Earth). The next new moon for us is December 22. When is the next new moon for people living on the opposite side of the Earth? a. December 8 (today) b. December 15 c. December 22 d. December 29 3. First, remove Earth’s atmosphere; then, climb to the roof of the UW Tower and drop a hammer and a feather. What is the physical explanation for the objects falling at exactly the same acceleration? a. The larger force needed to accelerate the hammer comes from the equally larger mass, so the acceleration of the hammer and feather remains the same. b. Everyone knows that objects fall at the same rate on Earth, 9.81 m/s2. c. The mass of the Earth is so much greater than the mass of even the hammer that the gravitational force on each object is identical. d. Because the feather has more inertia than the hammer, it is able to fall to the Earth faster and thus will hit the ground at the same time as the hammer. Figure 2. A recreation of the astronauts on the Moon experiment 4. Superman left the planet Krypton as an infant 27 years ago just before its destruction. Krypton orbited the star Caph, a spectral type F star. Caph is 54 light years away; thus Superman could have looked back in time and seen his home blow up. Here’s the question: The full spectrum of light was emitted during the explosion of Krypton. Which kind of signal reached Superman first and why? a. X-ray signals because x-rays have the high energy, high frequency, and thus faster speed. b. Radio signals because although they have the lower energy, the wavelengths are very long. c. Visible light captured by the Hubble Space Telescope because of its being above the atmosphere. d. All are forms of electromagnetic radiation traveling at light speed and thus reached us at the same time. 9 December 2014 final-exam_autumn2014-analysis.docx 1 5. Which one of the following statements is NOT correct about the relationship among the luminosity, surface temperature, and overall color pattern of a star? a. The luminosity, surface temperature, and overall color pattern of a star are related. b. The cooler a star is, the less luminous it is, and its spectrum will peak at longer wavelengths. c. The hotter the star, the more luminous it is, and the brighter the colors will be overall. d. For stars having orbiting planets, if the surface temperature of a star increases, its luminosity does not. DIRECT from one of the quizzes Figure 3. Thermal radiation curves of four stars. 6. What information about these 4 stars could be inferred directly from values on this chart? a. The approximate distances they are from Earth in parsecs. b. Whether or not they will go supernovae or form planetary nebulae. c. Fairly reliable estimates of their surface temperatures. d. Their parallax shifts when their luminosities are known. 7. What is the difference between the interstellar medium (ISM), a molecular cloud, and a protostar? a. The ISM contains everything: hot gas, dust, molecular clouds, stuff not part of a protostar. b. The only difference is density: protostars are less dense than the ISM and molecular clouds. c. The ISM is a broad category that excludes molecular clouds, protostars, and also HII regions. d. The ISM is much cooler and denser than either a molecular cloud, an HII region, or a protostar. 8. You have examined images of cool dust shown glowing in “false” colors. The colors represented have to be called “false” because the overall blackbody (thermal) curves peak at wavelengths a. in the ultraviolet part of the spectrum. b. in the visible part of the spectrum but at colors unknown to us. c. in the infrared part of the spectrum. d. that are much longer than microwave wavelengths. 2 Figure 4. Cut away of the Sun (left) and approximate temperatures above the photosphere and to the core. The heights in the right-hand figure are not exact. A points to dark features on the photosphere, which is represented by B. Use Fig. 4 to answer the next 5 questions. 9. (1 pt) Contains the coolest region where absorption lines form. B 10. (1 pt) Energy gets through this region via the “random walk.” D 11. (1 pt) Magnetic fields from Sun’s interior poke out in these photospheric dark regions. A 12. (1 pt) The “boiling” movement of the gas transports energy through this region. E 13. (1 pt) The only region where fusion occurs. C 14. Both of the following statements are either True (a) or False (b): If a star has an apparent magnitude of 5 it is brighter than a star whose apparent magnitude is 8. If a star has an absolute magnitude of −6, it is more luminous than a star whose absolute magnitude is −1. Covered in lecture, covered when working on the CMDs, covered indirectly with the distances to the clusters, included on an HR Diagram…. 15. Particles and energy are produced in the proton-proton fusion cycle of the Sun and other stars. What part of the fusion cycle is most responsible for supporting the Sun against gravitational collapse? a. the neutrinos that are formed in the first step. b. the positrons that are formed in the first step. c. the gamma rays that are produced in steps 1 and 2. d. the two protons released at the end when the helium nucleus is created. What does the fusion process produce? Neutrinos go straight out unimpeded; positrons annihilate with electrons to produce gamma rays; two protons at the end only get put back into the next fusion process. We worked through the whole proton-proton cycle sheet in lecture, and the image was included in the cover sheet with the exam. TO BE REGRADED. Spectral Apparent V Parallax Star Name Type Magnitude (arc sec) Asellus Borealis A1 IV 4.67 0.018 Asellus Australis K0 III 3.94 0.025 Acubens A5 V 4.26 0.017 Al Tarf K4 III 3.52 0.011 kappa Cancri B8 III 5.24 0.006 Figure 5. The constellation Cancer and named and numbered stars (Star information gathered from SIMBAD.) The constellation Cancer will cross the meridian at midnight on February 2, 2015. Review the data listed in the above table on 5 of its brightest stars and answer the following 4 questions. 16. (1 pt) Which of these two stars – a. kappa Cancri (0.006) or b. Asellus Australis (0.025) – is farther away? 3 17. (1 pt) Which of these two stars – a. Acubens (A5V) or b. Al Tarf (K4III)– has a higher temperature? OBAFGKM 18. (1 pt) Which of these two stars – a. Al Tarf (3.52) or b. kappa Cancri (5.24) – is brighter? Smaller apparent magnitude means brighter. Emphasized many times in lecture; worked on in fitting the main sequences of the clusters. 19. Asellus Australis and Al Tarf are both K giants, with close to the same brightness, and yet Al Tarf is over two times farther away. Which star must be more luminous? a. Asellus Australis b. Al Tarf c. Not enough information is given to answer this question. Same brightness in the sky, but one is 2 times farther away. The one that is farther away has to be more luminous if it is farther away but has the same brightness in the sky. There are two open clusters “in” Cancer, Messier 44 (Praesepe) and Messier 67, indicated by the circles, arrows, and labels in Fig. 5. Here are their actual color-magnitude diagrams. 20. Which cluster is older? a. Messier 44 (M44) b. Messier 67 (M67) 21. If a main sequence star in M44 with B - V = 1 has an apparent magnitude of 13.5 and a main sequence star in M67 with B - V = 1 has an apparent magnitude of 16.5, which cluster is farther away? a. Messier 44 (M44) b. Messier 67 (M67) c. Not enough information is given. Cluster fitting activity; also, along the main a. Praesepe b. Messier 67 sequence, stars have same mass that have same temperature and have same luminosity ! a primary feature of the HR Diagram. Thus, at a given temperature, the dimmer the star, the farther away the cluster is. Figure 6. The color-magnitude diagrams of 2 open clusters in the constellation of Cancer.