Slashdot Mirror
Looking For Earth-Like Exoplanets
Discover Magazine is running a story detailing the search for planets like Earth orbiting other stars. While we've been able to locate a few "super earths" so far, none of them really compare in size or the potential for habitability with our own world. Fortunately, advances in data analysis and new space-based telescopes — such as Kepler, the James Webb Space Telescope, and the already-launched CoRoT (PDF) — have some astronomers predicting we'll find such an exoplanet by 2010, and a habitable one by 2012. Earth-based telescopes are also in the hunt, though the article notes, "even if a habitable Earth-like world is found first from the ground, it will most likely take a space observatory to search for the chemical signals that tell us what we really want to know: Is anything living out there? If the planet is one that can be observed transiting, it just might be possible to provide a hint of an answer in the next few years."
Obsessed with the fact we haven't observed something we can't yet detect... This must be some sort of mis-post.
It's harder than that. I assume by "see" you mean two-dimensional visible or near-visible light images. To produce images like that you have to be able to move each telescope in your interferometer (or have lots of them), in two dimensions. The big radio interferometers put the radio telescopes on train tracks. Some proposals for space interferometers put one on each end of a tether, spin them, then winch them closer and farther apart to trace out a spiral.
The other problem with crazy long baseline interferometry is that you need to transmit the received signal (including phase) between the individual elements. For radio that's not too bad because you can actually detect and record the phase, for low enough frequencies. For optical it's much harder.
Plus you have the problem that interferometers have great resolution but poor light gathering capability. They can't see things that aren't bright.
A back of the envelope calculation (which might be wrong) shows that a 50 km city at 50 light years would be about 2 x 10^-5 miliarcseconds. To get that kind of resolving power in the middle of the visible spectrum you'd need a telescope about 6000 kilometres across. That's not too insane. You might be able to pull it off with an array of a hundred or so reasonably sized space telescopes all orbiting around a L point somewhere. If you could collect enough light, and distinguish between the city light, the non-city planetary light and the star, of course.