WebQuiz Quiz: 5
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WebQuiz 5
please complete by midnight, Thursday, Feb. 21
Utilities > Submissions > View submission by MILLER, SCOTT (STM10) on 2/25/2008 10:24:09 PM
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1. What characterizes the T Tauri phase of protostellar evolution? A. fragmentation of a molecular dust cloud into large irregular regions B. violent surface activity resulting in strong protostellar winds C. stable nuclear burning at a fixed location on the H-R diagram D. evolution of a low-mass star off of the main sequence into a red giant E. initiation of nuclear fusion
The T Tauri phase occurs as a protostar generates strong surface winds, blowing away the surrounding cloud of gas and dust. See lesson 15 for details.
Points Earned: 60/60 Correct Answer: B Your Response: B
2. How did Mercury's location in the solar system affect its composition? A. Mercury is rich in metals because only metallic grains could survive the high temperatures so near the Sun. B. Mercury is poor in metals because metallic grains could not survive the high temperatures so near the Sun. C. The nearby Sun caused ice in Mercury's interior to melt into liquid water. D. Because Mercury is so near the Sun, its composition is similar to the Sun; mostly hydrogen and helium.
Mercury is highly metallic, due in part to the fact that it formed closest to the Sun, where mostly metals condensed out of the solar nebula gas when the planets formed. See lesson 15 for details.
Points Earned: 60/60 Correct Answer: A Your Response: A
3. When does a protostar "officially" become a star? A. When it expels a high-speed wind, blowing away surrounding dust and gas. B. When hydrogen begin fusing into helium in its core. C. When gas and dust surrounding the protostar settle into a disk structure. D. When magnetic fields reach a critical level.
A protostar "officially" becomes a star when its core becomes dense and hot enough to fuse hydrogen into helium. At this point, enough energy is generated to halt the collapse of the star, placing it in hydrostatic equilibrium. See lesson 15 for details.
Points Earned: 60/60 Correct Answer: B Your Response: B
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Quiz: WebQuiz 5
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4. Rank the following based on the Earth's transparency at each wavelength range. (1 - completely transparent, 2 partially transparent, 3 - completely opaque). A. radio B. infrared C. visible D. ultraviolet E. X-ray F. gamma ray
The Earth's atmosphere is completely transparent in the optical (visible) and radio portions of the spectrum, partially transparent at infrared and ultraviolet wavelengths, and completely opaque at X-rays and gamma rays. Therefore, the different types of radiation would be ranked (completely transparent to completely opaque): visible & radio, infrared & ultraviolet, X-rays & gamma rays. See lesson 13 for details.
Points Earned: 60/60 Correct Answer: A:1, B:2, C:1, D:2, E:3, F:3 Your Response: A:1, E:3, B:2, C:1, F:3, D:2
5. (Choose all that apply). The largest optical telescopes are reflecting telescopes because A. refracting telescopes suffer from chromatic aberration, but reflecting telescopes do not. B. glass can absorb a portion of the light entering a telescope lens, while mirrors do not. C. lenses can only be supported around its edge, so large lenses tend to deform under it's own weight. Mirrors can be supported along their entire back surface, so larger mirrors can be used. D. it's easier to accurately shape one side of a mirror than two sides of a lens.
All of the above are reasons why astronomers favor reflecting telescopes over refracting telescopes when building large telescopes. See lesson 13 for details.
Points Earned: 60/60 Correct Answer: A, B, C, D Your Response: A, D, C, B
6. The last decade of the twentieth century saw enormous advances in techniques used for the discovery of extrasolar planets. In general, what was true about these techniques? A. could They only find planets in systems in which there were a large number of massive planets orbiting a star. B. They could only find planets for stars within about two light-years from Earth. C. They were based on photographic detection of objects orbiting nearby stars. D. They were biased toward finding massive planets rather than smaller ones.
At the moment, we only have the technology to discover "Hot Jupters"; massive planets close to their stars. This is because the larger the mass of a planet, the more it causes its parent star to wobble. The closer the planet is to its star, the faster the star wobbles. We currently don't have the technology to detect the wobble of a star due to an Earth-like planet. See lesson 16 for details.
Points Earned: 60/60 Correct Answer: D Your Response: D
7. Why is dust important to the condensation theory?
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Quiz: WebQuiz 5
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A. The solar nebula gas was composed only out of hydrogen and helium. All other elements were present in the dust. B. The presence of dust helped trap in heat from the Sun, allowing the planets to stay molten longer during their formation stage. C. Without dust, the gas particles would have nothing to condense onto.
Without the presence of dust in the solar nebula, the gases would not have anything to condense out onto, which is a major step in the process of planet formation. See lesson 15 for details.
Points Earned: 60/60 Correct Answer: C Your Response: C
Fill in the blanks to complete the definitions for the three type of nebulae listed. For the first two blanks in each definition, use one of the following words: gas, dust, absorbs, emits, scatters. For the last blank, fill in the blank with a single color. 8. Dark Nebulae _____ in the nebulae _____ light from background objects. Dark nebulae appear _____.
Dark nebulae are caused by dust in a cloud absorbing and blocking background light from reaching us. Because of this, the clouds look dark (or black) relative to the light from the background objects. See lesson 14 for details.
Points Earned: 60/60 No. Student responses Grade Correct answer (Value) 1. 2. 3. dust absorbs black 34% 33% 33% dust (34%), black (33%), absorbs (33%) dust (34%), black (33%), absorbs (33%) dust (34%), black (33%), absorbs (33%)
9. Emission Nebulae - _____ in the nebulae _____ energy in the form of light, received from nearby hot stars. Emission nebulae appear _____.
Emission nebulae are clouds of gas which are being ionized by nearby hot stars. After absorbing the energy from these hot stars, the gas re-emits the light. Since the clouds are mostly hydrogen, they emit mostly red light in the visible spectrum, giving them a characteristic red or pink color. See lesson 14 for details.
Points Earned: 60/60 No. Student responses Grade Correct answer (Value) 1. 2. 3. gas emits red 34% 33% 33% gas (34%), pink (33%), red (33%), emits (33%) gas (34%), pink (33%), red (33%), emits (33%) gas (34%), pink (33%), red (33%), emits (33%)
10. Reflection Nebulae - _____ in the nebulae _____ light preferentially from nearby stars. Reflection nebulae appear _____.
Reflection nebulae are created when light from nearby stars passes through a cloud of dust. The dust scatters visible light, but it scatters short-wavelength (blue) light more than it scatters long-wavelength (red) light. This blue light gets scattered through the cloud, some of it ultimately scattered towards us. This gives the cloud a characteristic blue color. See lesson 14 for details.
Points Earned: 60/60
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Quiz: WebQuiz 5
https://cms.psu.edu/section/content/Default.asp?WCI=pgTool%5FQuiz...
No. Student responses Grade Correct answer (Value) 1. 2. 3. dust scatters blue 34% 33% 33% dust (34%), reflects (33%), blue (33%), scatters (33%) dust (34%), reflects (33%), blue (33%), scatters (33%) dust (34%), reflects (33%), blue (33%), scatters (33%)
Done
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