Looking Up: What You Can See: Practice Problem Solutions

1. About 2,000 to 2,500.

2. Mercury, Venus, Mars, Jupiter and Saturn.

3. Any two of: planets twinkle less (steadier light); planets slowly move against the star pattern from week to week; planets stay near the ecliptic.

4. The magnitude +1 star is brighter, because smaller numbers are brighter. A difference of 3 magnitudes is about 2.5 x 2.5 x 2.5, or about 16 times.

5. A star is a tiny point of light, and moving air bends and flickers it. A planet is a small disk, so the flickering averages out.

6. About 20 to 30 minutes. Red light barely affects the dark-adapted eye, while white light resets the adaptation.

7. It is our own galaxy seen from inside: billions of stars so far away that they blend into a glowing band.