03-Parallax

# 03-Parallax - [R4 James Dalessio 2011 3 Parallax PreLab...

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3. Parallax - PreLab Name: Section: Date: Distant Stars are Points of Light We can separate the top from bottom, left from right, and see features on an object that is “resolved”. The size of a resolved object in the sky is directly related to the size of the object and its distance from us. Most everything we see in day to day life is resolved. We can see the left and right parts of a billboard separately and read letters written on it. If the billboard is closer it appears bigger. The moon and sun are resolved. We can see craters and details on the moon and we can see spots on the sun. If you were to write the word HELLO in giant letters on the sun we could read it (don't try it, you'll burn your eyes out). An object that is “unresolved” appears as a blurry point no matter its real shape. The size of an unresolved object does not depend on how bright or how big it is. Distant objects, like most stars, are so far away that they are very very tiny in the sky. Our eyes and most telescopes are not powerful enough to actually see something so very small so instead we see a blurry point of light. Its like the last line of letters on an eye doctors examination board. Even if the star were not a sphere we would still see a little round blurry point of light. If someone was to write the word “HELLO” in huge letters across a distant star we would be unable to read it or even tell that there were letters there. We say these objects are “unresolved”. We sometimes get the feeling that certain stars in the sky appear bigger than others. This is not true. The size of an unresolved object depends only on how good your eyes (or telescope) are and how nice the weather is. (2) Question 1 : There must be objects that are barely resolved. If we were to take the sun and move it further and further away it would appear smaller and smaller. Eventually it would become unresolved. Just before it became unresolved how big would it appear when compared to an unresolved object? (2) Question 2

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## This note was uploaded on 02/01/2012 for the course PHYS 133 taught by Professor Staff during the Fall '08 term at University of Delaware.

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03-Parallax - [R4 James Dalessio 2011 3 Parallax PreLab...

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