Quote:
Originally Posted by korjik
Using Hypo' Testings numbers:
resolving angle= width/distance
goes to
Distance= width/ resolving angle
D= 1.2x10^6 m / 3x10^-10
D= .4x10^16 m= about .4 light years
so an earth sized exoplanet would be harder to resolve if it were further away then .4 light-years.
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great.
The closest earth-like planet would be further than 4 LY. So to resolve this planet would take
angle = 1.2X10(6) / 4 X 10(16) = 3 X 10^-11 radians = 5 X 10^-6 arc-sec.
Wow! Also, to resolve continents on these planets would take even more resolution.
To estimate the size of aperature required:
diffraction limit angle = (wavelength)/ diameter
diameter = wavelength / angle = 5 X 10^-7 / 3 X 10^-11 = 20 kilometer (aprox.).
So I would conclude we need an optical interferometer at least 20 km in effective diameter to resolve the closest earth-sized planets. To really get medium distance exoplanets and resolve surface features would probably take about a 1,000 km optical interferometer array (with great computing and navigation/pointing ability). Is NASA/ESA planning such an array (or something in that ball-park to resolve earth-like planets). They'd probably use coronographs to reduce starlight also.
When I was young, some texts taught that imaging exoplanets was sci fi. But I'm not so sure any more. We could quibble about what the major advances since then are, but I think computers and electronics were the biggest advance . I think NASA/ESA will someday (maybe 20 years?) show images of exoplanets.