Light from a star that is truly 70° from overhead comes down through the air…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Light from a star that is truly from overhead comes down through the air. Treat the air as flat layers, with at the ground, so that . How much higher does the star look, in minutes of arc ( minutes )?
Need a reminder? The key ideaShow
The air is denser near the ground, so starlight bends as it comes down. Stars look higher, and they twinkle as the air moves. The Sun is seen about before true sunrise and after true sunset.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The angle seen. , so the angle seen is from overhead.
Step 2. The lift. .
Step 3. In minutes of arc. minutes of arc.
Answer: about minutes of arc higher.
Check. It is tiny, but stars near the horizon are lifted more; at the horizon the real lift is about half a degree.
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