Jan 19

Dr. Mitchell AAS

Dr. Robert Mitchell gave a presentation on the American Astronomy Convention and his participation.   Brian Didier and Shivani Ganesh were two undergrad students who worked with me over the last few years on my research. A spectrum is blueshifted if the object is moving toward you. In this case, it’s the photosphere (“surface”) of the supernova that’s rapidly moving toward us because of the explosion (on the order of 10,000 miles per second). The amount of blueshift in the spectral lines tells us just how fast. Assuming the photosphere is expanding at constant velocity during the supernova’s entire life (which is reasonable, since at these speeds, gravity would hardly slow it down at all), then the velocity times how long it’s been since the explosion gives us the radius of the photosphere The overall spectrum has a shape that depends on the temperature of the supernova’s “surface”. A theoretically perfect radiator of “heat radiation” (which only depends on the temperature of the object) is called a blackbody. For a blackbody, the absolute brightness depends only on the radius and the temperature. Comparing the absolute brightness to the apparent brightness gives us the distance to the supernova, and therefore to the […]

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