Hi Joe, Interesting questions. The real optical guys on the list will have me for lunch, but it would seem to me that building an occluding mask for such a situation might be a real trick. The success of a mask actually depends on a star being more than a point source. If a mask is only a point--besides the geometric impossibility of fabricating it--then it wouldn't really block any light at all. The mask would then have to be the exact diameter neccessary to block the disk of the star. While not a point, it would be pretty darned small. If it's too small, starlight would get past it and wash out a planet. If it's too large, it might occlude the planet as well as the star. If you got past that, there are still a great many issues concerning the resolving power of the scope. It would either have to be very large or would have to be a fleet of spaced scopes doing interferometry. I believe there's a NASA proposal for just such a project, minus the occluding mask. Given NASA's current infatuation with sending people to Mars, who knows when we get back to science... --MC -----Original Message-----

From: Joe Bauman <bau@desnews.com> Sent: Apr 13, 2006 1:03 PM To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: [Utah-astronomy] Can't quite figure this one

I have an optics question. A recent article mentioned how hard it would be to detect the tiny speck of light emitted by an exoplanet, because of the overwhelming brightness of the parent star. Fair enough. However, if a telescope in space were to use a tiny device to block the star's light, you'd think that would allow a view of the planet. -- I'm sure that's not right. But why isn't it? In space, isn't a star basically a point source? I would exepct no light scattering in what is essentially a vacuum. So what's wrong with that idea? Thanks, Joe

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