* Astronomy

Daniel Goldin envisioned an initial flotilla of large "terrestrial planet finder" telescopes ("TPF" for short), capable of locating Earth-sized exoplanets and even imaging them - but as no more than smudgy dots. If the TPFs found promising worlds, more ambitious "planet imager" telescopes could then be built, which would operate in unison to deliver Goldin's promised maps of alien earths.
Viewed across the light-years, a world like Earth would appear extremely close to its star; distinguishing the former from the latter would be very difficult. Marc Postman, an astronomer at the Space Telescope Science Institute, compares the feat to reading the date stamped on a dime at a distance of 5 kilometres. Worse yet, the star may outshine the exoplanet by a factor of 10 billion. To get even a meagre clump of exoplanetary pixels, a TPF telescope must somehow eliminate the star's glare so that the faint exoplanet's light can be seen. It would be like photographing a lit match on the cusp of a detonating hydrogen bomb.

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