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Astr 122

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ASTR 122
05/13/2013
Assignment #3
951131748
WangJae Lee
Astronomy 122 Distance Education Third Homework Assignment 1. Explain why measuring parallax distances for only the brightest appearing stars in the sky would give you a biased luminosity scale and an unrepresentative sample of stars.
-The stellar parallax measures the relative distances from stars to different positions of the Earth in order to measure luminosity. It is done by using distant stars as a fixed reference system so that if a star is observed in respect to the distant stars today, and then measured again in six months, a small shift in movement will be recorded. It is absolutely necessary for there to be “distant stars” or less bright stars as a frame of reference otherwise the angle measurements would have nothing to compare against. Thus, it creates a biased scale of recorded luminosity. 2. Explain the overall concept of pressure support (against gravity) in stars and why stars are unstable if they are not generating energy in their cores. -The concept of pressure support can be explained through the internal gas pressure. The internal gas pressure is attempting to expand and dissipate our ball of gas, while the self-gravity of the gas (due to its mass) is trying to collapse the ball. As the gas gets hotter, the internal gas pressure increases. Then, it reaches a point of stabilization between gravity and pressure support. -Stars are unstable if they are not generating energy in their cores because the energy generation prevents the collapse of the star. Energy generation is occurring in its core, and this provides gas pressure which prevents collapse of the star. Thus, if the stars are not generating energy, they would be unstable. 3. For low mass stars, the relation between their luminosity (intrinsic energy output) and their mass is the following:
L α M4
(in words this means

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