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Unformatted text preview: Answer: Let R be the Earth-sun distance and x the distance to the
star in question. Thus, tan (θ / 2) = R / x. With θ = 2° and R = 93 million miles,
x ≈ 5.33 × 109 miles
The Star Schmedrick is looking at is approximately 5 billion miles
away. So, Schmed must have been imagining this star, because it’s
much too close for any real life star (other than the sun). R
x 2o Luminous vs. Illuminated
A luminous object is a body that produces its own light such as
the sun or a light bulb.
An illuminated object is a body that reflects light, just like the
moon, people, and buildings.
Some objects, like water and glass, transmit light to some
extent. In order to be seen, light must come from an object one
way or the other. Luminosity & Magnitude
Luminosity is the rate at which energy of all types, and in all
directions, is radiated by an object. The luminosity of a star depends
on its size and its temperature: L ∝ R 2 T 4. The sun is a mediumsized star with a luminosity of 3.8×1026 J/s. The known luminosities of
stable stars range from about a millionth that of the sun for a
relatively cool white d...
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- Fall '11