ASTChapter7 - Chapter 7-Supernova 1987A lessons and enigmas...

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Chapter 7-Supernova 1987A: lessons and enigmas 7.1 The Large Magellanic Cloud Awakes First supernova easily observable with naked eye since Kepler 1604 Proved basic observances of how a star explodes are correct. Exploded in nearby galaxy, not Milky Way --Cannot be seen from the northern hemisphere --Magellan: first European to record it while he sailed around the world (Large Magellanic Cloud) --people in southern hemisphere already knew of it. Aborginies—called it Calgalleon. --small companion: Small Magellanic Cloud (Gnarrangalleon) --neither spiral nor elliptical; irregular. Has a large central band of rather young, newly formed stars, but then more distended array of older stars -one side of central band: intense region of star formation ( 30 Doradus/Tarantula nebula). Has young cluster of very massive stars, 100 solar masses. Surrounding middle 30 Doradus, large patches of gas and dust/massive stars, young but older than core cluster of Doradus. LMC is 150,000 light years away. Milky Way is 50,000 across. Andromeda Galaxy (Messier 31). 2 million light years away and is sister spiral galaxy to Milky Way nearest cluster of galaxies is 50 million light years away LMC’s nearness is why SN 1987A looked so bright. Actually exploded 150,000 years ago. Gave enough time to come up of new technology to pinpoint SN LMC is immature: has not processed as much of its gas through stars as has Milky Way. Heavy elements in LMC is ¼ that of Sun 7.2 The Onset SN 1987A—discovered and first formally reported on Feb 23, 1987 by Ian Shelton. Used small telescope at Las Campanas Observatory in Chilean Andes. First person actually to see it was night assistant Oscar Duhalde who stepped out for cig and saw it but didn’t think any of it. It was only hours old. At same time in Australia, Rob McNaught was surveying sky of asteroids and went to bed without developing plates. After hearing of Shelton’s finding, he developed his images and had first permanent recording of light from the supernova 7.3 Lessons from the Progenitor SN 1987A has evidence of a star that existed before it exploded; rare case; Sk-69 202 Nothing really special about the star. -Did not vary in light output -Did not have any anomalous emission lines -Did not appear to be shedding mass at an especially noticeable rate or in a special way Star 1-Sk-69 202 Star 2-less massive than Sk-69 202. Several light years away from sk-69 202, but probably born in same burst of star formation that gave rise to Sk-69 202 and other fainter stars. When SN went off, vicinity of supernova was lost in the image due to the intense explosion. Faded first in the UV and star 2 could be identified.
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Lingering UV image: was the wrong progenitor star identified? Star 3-showed that SN 1987A was not at the location of Star 1, but slightly offset
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ASTChapter7 - Chapter 7-Supernova 1987A lessons and enigmas...

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