Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

How big could an array of space telescopes acting as an interferometer be ?

How big would it have to be to resolve exoplanet surface detail the size of Iceland at a distance of 100 light years ?

share|improve this question

1 Answer 1

Well, with current or immediate-future technology, let's use LISA as an example of the largest baseline achievable at $5\times 10^6$ km. Then the diffraction limit says $\theta \sim \frac{\lambda}{D}$, where $\theta$ is angular resolution, in this case ($10^7$ cm)/($10^{20}$ cm)=$10^{-13}$ radians. At optical wavelengths, the LISA-type detector would have resolution of $10^{-16}$, so yes, in principle, this seems possible.

The biggest problem I think I am ignoring is flux: there wouldn't be enough photons coming from exo-Iceland to do proper interferometry, and then there is also the problem of contrast: what is the difference in flux between land and sea features, aside from contrast with host star.

With current radio telescopes, a much-quoted factoid is that you could read the date on a dime on the moon, but in practice you never could because it doesn't emit in the radio, and certainly not with that contrast in signal.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.