Homework III MCQs - Astronomy II | ASTR 1020, Assignments of Astronomy

Download Homework III MCQs - Astronomy II | ASTR 1020 and more Assignments Astronomy in PDF only on Docsity! Astronomy II (Astr 1020) Spring 2008 Prof Richard Ignace HOMEWORK #3 Notes: You will need a calculator, a pencil, and a standard scantron. Each question has one correct answer. Choose the best answer for each. Mark your answer on the scantron. This homework is due at the beginning of class on February 21. Late homeworks will not be accepted. 1. Among this list, the most common stars are a) A stars b) B stars c) G stars d) M stars e) O stars 2. A parsec is a) the distance between the Earth and the Sun. b) the diameter of the solar system. c) the distance light travels in a day. d) the distance of an object with a parallax of 1 arcsecond. e) the distance between the Sun and the nearest star. 3. Main sequence stars a) all have the same size b) are stars which have no hydrogen or helium c) are objects which are mostly made of hydrogen d) have nuclear fusion of hydrogen occuring in their cores 4. Hydrostatic equilibrium is the balance of a) pressure and nuclear forces. b) gravitational and pressure forces. c) magnetic and gravitational forces. d) nuclear energy production and radiation loss from the Sun’s surface. e) None of the above. 1 5. Star A and Star B have the same luminosity; however, star A is hotter. You can conclude a) star A must be closer in distance. b) star B must be closer in distance. c) star A must be larger in radius. d) star B must be larger in radius. e) nothing, for it is impossible for two stars to have the same luminosity if they do not have the same temperature. 6. Why would it be easier to measure parallaxes from Pluto than from Earth? a) Pluto is closer to other stars than the Earth. b) Pluto is colder than the Earth. c) Pluto has a lower temperature than the Earth. d) Pluto’s orbit has a larger semimajor axis than the Earth’s orbit. e) Pluto’s orbit is more stable than the Earth’s orbit. 7. If a star is of spectral type M, a) it is blue and relatively cool for a star. b) it is red and relatively cool for a star. c) it is blue and relatively hot for a star. d) it is red and relatively hot for a star. e) its spectral type is not related to its color or temperature. 8. Why is a main sequence high mass star hotter than a main sequence low mass star? a) Because the high mass star requires a greater temperature to support it against gravity. b) Because the high mass star has more hydrogen available for fusion. c) Because the high mass star emits more ultraviolet radiation. d) The statement is false. High mass main sequence stars are not always hotter than low mass main sequence stars. 9. Cool star spectra can show absorption features from molecules but not so for hot star spectra. Why? a) Hot stars lack the right kinds of elements to form molecules. b) Molecules cannot survive at high temperature because they become dissociated. c) Cool stars lack hydrogen so that molecules are easier to form. d) Hot stars have too much hydrogen to form molecules. e) Spectral features of molecules in hot star atmospheres are present only as emission lines, not absorption lines. 10. How did the gas in the cold interstellar cloud that became the Sun get hot enough for nuclear fusion? a) Gravity compressed the gas. b) Chemical reactions released energy. c) The proton-proton chain released energy. d) The CNO cycle released energy. 2