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2 identical stars have different apparent brightnesses. 1 star is 10 light-years away,...

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faithlovehope | Student | Honors

Posted April 26, 2010 at 1:10 PM via web

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2 identical stars have different apparent brightnesses. 1 star is 10 light-years away, the other is 30. Which star is brighter, and by how much?

Two identical stars have different apparent brightnesses. One star is 10 light-years away, and the other is 30 light-years away from us. Which star is brighter, and by how much?

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krishna-agrawala | College Teacher | Valedictorian

Posted May 2, 2010 at 2:07 AM (Answer #1)

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The brightness of an object as perceived by human being depends on many factors. The most important of these is the amount of light energy reaching the retina of our eyes. For an object of same brightness the energy falling on retina gets reduced with the increase in distance of the object from the observer. This is because as the distance of an object increases the same amount of light energy emitted by the it gets distributed over larger area.

Therefore, between two stars of that have equal apparent brightness, one that is farther will have be brighter in reality. Thus in the given example the star situated 30 light years away will be brighter than the star situated 10 light years away.

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sfstudent | Student, Grade 9 | Honors

Posted April 26, 2010 at 3:43 PM (Answer #2)

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i think the closer star is more brighter, obviously because it is closer to us, and the closer star is brighter by 3 times than the other star.

well thats what i think.

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