# Homework Help: Angular Diameter Eclipse Question

1. Aug 11, 2010

### Pronitron

1. The problem statement, all variables and given/known data
The moon Titan has an angular diameter of 4.4mrad as seen from the surface of Saturn. The sun has an angular diameter of 9.3mrad as seen from the surface of the earth. Which of the following eclipses cannot be seen from the surface of Saturn
(a) A lunar eclipse of Titan by Saturn
(b) A partial solar eclipse due to Titan
(c) A total solar eclipse due to Titan
(d) An annular sola eclipse due to Titan

2. Relevant equations

I have no idea, I'm guessing perhaps equations involving angular speed/frequency/period?

3. The attempt at a solution
So I have just completed my AS levels and have never encountered any prior work that is similar to this question, therefore I'm at a complete loss as to where to begin or how to answer the question. My guess would be that the total solar eclipse could not happen as Titan has a smaller angular diameter than the sun so would not totally block the light but I am not sure. If someone could explain the answer to me (as this is all completely new to me) then that would be much appreciated. I looked on wikipedia and it talked about angular diameter in terms of arcseconds so I'm not sure what that means. Thank you.

Last edited: Aug 11, 2010
2. Aug 11, 2010

### zhermes

This problem requires virtually no knowledge of astronomy/physics; I think you're just making it way too complicated (note that mrad and arcseconds are both just measures of angles, the detailed conversions don't matter).
Imagine yourself on saturn, what do the numbers given mean?

3. Aug 12, 2010

### Pronitron

Well I assume it means the diameter of the planet as you see it from your position, such that the moon appears roughly half the size of the sun when viewed from Saturn relative to the size of the sun in the sky viewed from the earth, but then this is all depends on the distance you are from the objects right, and I know the sun is obviously larger, but the fact it does not give me their diameters from the same planet confuses me, because I don't understand what the point of telling me how big the sun appears from earth is when it's the size of the sun compared to Titan that I assume matters, perhaps the sun appears tiny from saturn and titan appears much larger so that it blocks the suns rays, I don't know because it only tells me it's size in the sky when viewed from the earth?