Speaking of gravitational lenses, our very own sun can be used as one:<p><a href="http://www.centauri-dreams.org/?p=22321" rel="nofollow">http://www.centauri-dreams.org/?p=22321</a><p>Key facts:<p>can work with existing technology<p>$5bn cost<p>long travel time, a century or so to the primary observation point (500-750au) but can visit several distant icy bodies before that point<p>100x magnification for infrared and visible-light (50-80x for radio and microwave) (only for object directly opposite the sun though)<p>a good precursor for an interstellar mission and<p>good study platform for the interstellar medium
paper - <a href="http://arxiv.org/pdf/1211.3663v1.pdf" rel="nofollow">http://arxiv.org/pdf/1211.3663v1.pdf</a> (the link and redshift, 10.8, are just under the image).<p>it's a photometric redshift derived from the lyman break. rest-frame ultra-violet emission less than 912 A is "completely" absorbed by intervening neutral hydrogen, and between 912 and 1216 A partially, in lines. so objects are dark at shorter wavelengths than 1216 A (in the frame of the galaxy). their observations show that in our frame there's no emission short of 1.46 um (infra-red). and 1.46e-6 / 1216e-10 ~ 12 = 1+z, so redshift is approx 11.<p>if it's correct (photometric redshifts are not as reliable as those obtained from spectra, but are technically easier to achieve, and this is really pushing the limits of what is possible - my partner, who is still in astronomy, is sceptical that this is real), then it's the most distant object known.<p>i guess the above isn't very clear. i'll try again. hydrogen gas just floating around in space absorbs ultra-violet (UV) light. so you don't see much UV from galaxies.<p>now distant galaxies are redshifted so much (by expansion of the universe) that the UV ends up in the infra-red (IR). so what you observe are things that are only visible in the IR - everything shorter (optical and UV) in our frame was absorbed (UV) in the galaxy's frame.<p>so one way to find extremely distance objects is to find things that can only be seen in the IR. what you're actually seeing is the redshifted optical; what you don't see in the optical is what, in the galaxy's frame, is absorbed UV.<p>but these galaxies are very faint, so they are hard to detect. using a gravitational lens boosts the brightness and so makes this technique more powerful.<p>i'm not sure that helps (a diagram would make things much clearer). the technique, well, the resulting objects, are called "lyman break galaxies". but i haven't found a good reference googling.
Isn't that awesome, the galaxy is huge, our planet is tiny, and yet all the objects in the whole galaxy have photons that reach our little planet, the lens of that specific telescope even. The photons traveled that far, that long, just to be finally absorbed by that telescope. What are the chances of a photon from an object that far away to hit specifically this location?