91Ó°ÊÓ

Explain the difference between a star's apparent brightness and its luminosity.

Describe how the parallax method of finding a star's distance is similar to binocular (two-eye) vision in humans.

Why does it take at least six months to make a measurement of a star's parallax?

Why are measurements of stellar parallax difficult to make? What are the advantages of making these measurements from orbit?

What is the inverse-square law? Use it to explain why an ordinary lightbulb can appear brighter than a star, even though the lightbulb emits far less light energy per second.

Briefly describe how you would determine the luminosity of a nearby star. Of what value is knowing the luminosity of various stars?

Why is the magnitude scale called a "backward" scale? What is the difference between apparent magnitude and absolute magnitude?

The star Zubenelgenubi (from the Arabic for "scorpion's southern claw") has apparent magnitude \(+2.75\), while the star Sulafat (Arabic for "tortoise") has apparent magnitude \(+3.25\). Which star appears brighter? From this information alone, what can you conclude about the luminosities of these stars? Explain.

Explain why the color ratios of a star are related to the star's surface temperature.

Would it be possible for a star to appear bright when viewed through a \(\mathrm{U}\) filter or a \(\mathrm{V}\) filter, but dim when viewed through a B filter? Explain.