At One Micro Arc Second, the disks of planets like Jupiter would be resolvable as far away as 3000 light years. Earth-sized planets orbiting nearby stars would be discerned as clearly as we see Jupiter with a 6" telescope. The motions of distant galaxies would be detectable in a single human lifetime, as would the motions of individual stars in nearby galaxies.
At One Nano Arc Second, the surfaces of planets orbiting Alpha Centauri are seen as clearly as Magellan now shows us Venus. We begin to resolve planets like Jupiter within the Andromeda galaxy, and the surface markings on individual red giant stars out to the Virgo Cluster. The motions of distant quasars would be discerned within a few years. Beyond this limit the mind reels at even more stupendous possibilities. Unfortunately, the laws of physics present us with three formidable obstacles to overcome in making these possibilities a scientific reality: High resolution necessarily means having to build large costly instruments; Not all surface details are bright enough to be seen at every conceivable, wavelength, distance and resolution; and finally, since everything in the universe is motion, we have only a limited amount of time to form a sharp image before the objects move and cause image blurring.
Compliments of Nature's quantum limitations on instrument size, background noise, and surface brightness, most of the regions in our mathematical universe of resolution appear as unreachable as the inside of a black hole. Even so, there is still much that could be done. To a distance of 3000 light years there would be over a billion stars to investigate, and potentially as many solar systems. Continents and weather systems on the planets orbiting the thousand or so nearby stars could under favorable circumstances be mapped and monitored for changes. Long before the first space probes are launched out of our solar system to discover Earth-like planets around other stars, astronomers will already have identified all such worlds out to hundreds of light years using One Micro Arc Second imaging technology, and at orders of magnitude lower costs.
This answer was updated in 2011.
See my books:
The Astronomy Cafe (1998) and
Back to the Astronomy Cafe (2003) for more FAQs in printed form. Author: Dr. Sten Odenwald, Copyright 2011
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