# Angle viewed form erath between sun and planet.

1. Oct 8, 2007

### hulkster1988

I'm having a hard time picturing this in my mind:

Calculate the largest possible angle as viewed from Earth between
the Sun and a hypothetical planet orbiting the Sun in a circular orbit with
a=0.65 AU. Assume Earth's orbit is circular and that Earth and the
hypothetical planet orbit the Sun in the same plane (coplanar orbits).

I assume the answer cant be 180 degrees as the sun would be blocking the viwer on earth from seeing the hyporthetical planet. So I'm stuck on trying to viualize the cutoff at hwich point a viewer from the earht would be able to see the hypothetical planet?

Thanks for any help.

Marc

2. Oct 9, 2007

### pixel01

You should take Venus as a reference. The highest angle possible of Venus seen from the Earth is about 45 degrees. Think about that.

3. Oct 9, 2007

### mathman

Place the three bodies (sun, earth, planet) in a tight triangle with the planet at the right angle point. Net result is angle=arcsin(.65).

The best was to view it is to draw a circle representing the orbit of the planet around the sun. Place the earth at some point ouside the circle, then draw a tangent from the earth to the circle. The angle between the tangent and the earth-sun line is obviously the largest angle.