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Unformatted text preview: Prep. for Quiz 4 (chapters 16, 17 and 18 of Cosmic Perspective) 1) Astronomers estimate that new stars from in our galaxy at the rate of about A) 20- 30 per year. B) one per year. C) 100 per year. D) a few (2- 3) per year. E) ten per year. 1) 2) By mass, the interstellar medium in our region of the Milky Way consists of A) 50% Hydrogen, 50% Helium. B) 70% Hydrogen, 28% Helium, 2% heavier elements. C) 50% Hydrogen, 30% Helium, 20% heavier elements. D) 70% Hydrogen, 30% Helium. E) 70% Hydrogen, 20% Helium, 10% heavier elements. 2) 3) What percentage of a molecular cloud's mass is interstellar dust? A) 28% B) 1- 50%, depending on the mass of the molecular cloud C) 2% D) 1% E) 50% 3) 4) What is interstellar reddening? A) Interstellar dust absorbs more red light than blue light, making stars appear bluer than their true color. B) Interstellar dust absorbs more blue light than red light, making stars appear bluer than their true color. C) The spectral line shift due to a star's motion through the interstellar medium. D) Interstellar dust absorbs more red light than blue light, making stars appear redder than their true color. E) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color. 4) 5) If you wanted to observe a molecular cloud, in what wavelength of light would you most likely observe? A) ultraviolet B) visible C) X- ray D) gamma- ray E) infrared 5) 1 6) What happens to the visible radiation produced by new stars within a molecular cloud? A) It is absorbed by dust grains and heats up the cloud. B) It escapes the cloud completely. C) It shoots out in bright jets. D) The blue light is absorbed and the red light transmitted. E) It is refected back onto the protostar, heating it up Further. 6) 7) The thermal pressure oF a gas depends on A) temperature only. B) density only. C) density and temperature. D) composition. E) gravity. 7) 8) The gravitational Force in a molecular cloud depends on A) density only. B) density and temperature. C) temperature only. D) thermal pressure. E) composition. 8) 9) What prevents the pressure From increasing as a cloud contracts due to its gravity? A) As the cloud becomes denser, gravity becomes stronger and overcomes the pressure buildup. B) Excess pressure is released in jets oF material From the young stars. C) The pressure is transFerred From the center oF the cloud to its outer edges where it can dissipate. D) Once the cloud reaches a critical density, the pressure becomes degenerate and independent oF temperature. E) Thermal energy is converted to radiative energy via molecular collisions and released as photons. 9) 10) What is the likely reason that we cannot ¡nd any examples oF the ¡rst generation stars?...
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This note was uploaded on 03/03/2011 for the course RSM 100 taught by Professor Oesch during the Spring '08 term at University of Toronto.
- Spring '08