Analyzing the Universe - Course Wiki: Ashes to Ashes, Dust to Dust

This week we explore the supernova remnant Cas A, so it would serve us well to learn more about these fascinating nebulae. For this portion of the wiki we will explore four well written education pages on supernova remnants. This reading is mandatory and you will be asked questions on the quiz relating to the material.

Supernova and Remnant Basics

Check out this great page from the California Institute of Technology that will help stitch together our understanding of supernovae and the remnants they leave in their wake.

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Supernova Remnants

Ranking among the most energetic of astrophysical events, supernovae result from either the core-collapse of a massive star or from a white dwarf whose mass is pushed toward the Chandrasekhar limit and ignites a thermonuclear explosion. In either case, the light from the original explosion (powered by radioactive decays that release photons) fades with time, and the dominant source of light results from the interaction of the forward shock with the star's ambient surroundings plus interactions with the reverse shock that heats the ejecta. The change in the dominant emission mode of radiation defines the transition between the supernova phase and the supernova remnant phase This is a bit artificial since the physics that explains supernova remnants and their shocks is happening while still in the supernovae phase, but is mostly hidden just like a candle held in front of a flood light is dimmed, even though it is there.

Our second reading assignment is an education page from Swinburne University that explains the shock structure and evolutionary phases of a supernova remnant.

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The third reading assignment is an education page from NASA's Imagine the Universe that explains different types, or categories, of supernova remnants and their dynamics. This article may prove especially crucial in solving a few of the problems on this week's quiz.

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The final reading assignment is a press release from Harvard's Center for Astrophysics reporting on Hiroya Yamaguchi's findings on the reverse shock in Tycho's supernova remnant. Pay careful attention to the analogy made about the reverse shock, which may help you to understand this phenomenon in a more concrete fashion.

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Below I have included a schematic of the two shock structure found in supernova remnants. This profile is a 1-dimensional representation with the x-axis being the radius (from the explosion center) and the y-axis representing the density of material. It is a "snapshot" in time, and approximates the current state of the Cas-A system. Understanding the particle density in these shocks is critical because the emission of radiation from these shock waves depends on the density of particles at a given location. Higher density implies more radiation.