We look toward a cool star. How can we determine that there is an ...

[ARLKQ]

We look toward a cool star. How can we determine that there is an interstellar dust cloud between us and the star?
 
  What will be an ideal response?

Question 2

Discuss the role that methane plays in the appearances of Neptune and Uranus.
 
  What will be an ideal response?

[djofnc]

Answer to Question 1

The temperature of the star is determined by spectral type and photometrically using the B and V filters. If there is no intervening dust then the two temperature determinations will agree. If there is dust, the photometrically determined temperature will appear lower than the temperature indicated by the spectral type because the starlight has been reddened. Dust cannot affect the spectral type.

Answer to Question 2

At Uranus and Neptune, methane is the chief coloring agent, absorbing red light strongly, and reflecting the blue light back into space.

[ARLKQ]

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[djofnc]

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