# If we were to see the Sun with our naked eyes from the Orion belt, would all planets be encompassed inside the star? Is this calculable?

When we see a star it looks much bigger in diameter to us than it really is, this picture (extracted from here) explains what I mean:

Notice that the point we see in the skynight, represented by the yellow outer circle, would actually encompass even planets orbiting the actual star, represented by the black dot in the center. In this case we see one planet inside the white circle.

My question is, can the effect of distance and brightness be measured as to know how far would we must be to watch a star that encompasses neptune?, the earth? or does it depend on different factors?

• I'm not sure I entirely understand your question. This is about diffraction, right? So, since the biggest factor would be the atmosphere itself (not accounting for any diffraction of the interstellar medium), where in the Orion belt would we be looking from? From a hypothetical planet similar to Earth with the atmosphere like ours, or in outer space and all we're interested in is diffraction of the ISM and our Sun's own heliosphere? Dec 24, 2013 at 21:16
• I didn't know the difference was caused by diffraction, this would've been part of the answer I was looking for. Thanks. Dec 25, 2013 at 2:07
• The observed image of a star is not a sharp edged circle. There are two effects which prevent us from seeing the actual stellar edge (which can be seen for the Sun). First, atmospheric seeing and second diffraction. The first jiggles the image on very short time scales (causing a sparkling appearance) and is caused by turbulence in the upper atmosphere. This effect may be quantitatively and/or qualitative different when observing from any other planet, say in Orion. Dec 25, 2013 at 14:00