Chapter 12: Visual Quiz Dan Bruton Part A The dark area stretching from the center of this picture to the upper right is about 50 light-years long and lies in the plane of the Milky Way Galaxy. What is it? A star-forming cloud. A region of the galactic plane in which there are very few stars. The expanding remains of a supernova. A black hole. Part B The main photo and the smaller inset both show the same field of view containing a star-forming molecular cloud. One of the photos was taken in visible light and the other in infrared light. Which one is the infrared photo, and how do you know? The smaller inset photo is the infrared one, which we can tell because edge of the cloud glows red in the image. The main (larger) photo is the infrared one, which we can tell because star-forming clouds generally are pink in color. The smaller inset photo is the infrared one, which we can tell because the cloud appears dark and infrared light is invisible. The main (larger) photo is the infrared one, which we can tell because cold molecular clouds emit infrared light but not visible light. Part C This is the HR diagram for stars in a 12_billion_year_old globular cluster. Based on your understanding of stellar lives, which of the four labeled stars is currently generating energy through hydrogen fusion in a shell around an inert (non-burning) helium core. III II I IV Part D This Hubble Space Telescope photo shows a planetary nebula. What is the white dot in the center (indicated by the arrow)? a red giant star with a strong stellar wind a white dwarf a neutron star a protostar that will soon become a main-sequence star Part E Suppose a particular star has a core that is undergoing several stages of fusion simultaneously, as shown in this diagram. Based on your understanding of stellar lives, the mass of this star is probably: about the same mass as the Sun about 2 solar masses more than 10 solar masses less than 0.1 solar masses Part F Suppose a particular star has a core that is undergoing several stages of fusion simultaneously, as shown in this diagram. Which of the following statements about this star is most likely to be true? The star is a red giant (spectral type M, luminosity class III). The star was born from a gas cloud with an unusually large proportion of elements heavier than hydrogen and helium. The star will explode as a supernova within a few days. A million years from now, all that will remain of this star is a white dwarf. Part G According to this diagram, how much more abundant is hydrogen in the universe than nitrogen? hydrogen is about 4 times as abundant as nitrogen hydrogen is about 30% more abundant than nitrogen hydrogen is about 10 times as abundant as nitrogen hydrogen is about 10,000 times as abundant as nitrogen Part H This photo shows the famous Crab Nebula. What is it? An expanding cloud of remains from a star that died in a supernova. A classic example of a planetary nebula. A star that is right now undergoing a supernova explosion. A star forming cloud that will eventually give birth to hundreds of stars Part I The arrow in the photo on the left shows the star that we see as a supernova in the photo on the right. What can we conclude about this star? It was a red giant star. It was a close binary star system. It was a high-mass star with at least 8 times the mass of the Sun. Before the supernova, the star lived for at least a billion years. Part J Suppose you had looked with your naked eye at the supernova on the night it was photographed in the "after" photo. Assuming that it was bright enough to see (it was), what would it have looked like to your naked eye? Like a huge white blob, about the angular size of the full Moon but not quite as bright. Like a single star in the night sky. Like a reddish cloud spread out over a region of the sky about half the angular size of the full moon. Like a pulsating bright light, dimming and brightening about every 5 minutes.
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