NASA's Jet Propulsion Laboratory, it will be possible to measure stellar positions to within 20 millionths of an arcsecond by 2005.

ECONOMIST: A roadmap for planet-hunting

Viewed from a distance of ten light-years, the sun's side-to-side wobble due to Jupiter causes its position to change by 1.6 thousandths of an arcsecond.

ECONOMIST: A roadmap for planet-hunting

It will have two telescopes mounted at opposite ends of a ten-metre boom, and will be able to measure astrometric wobbles as small as a millionth of an arcsecond.

ECONOMIST: A roadmap for planet-hunting

Already, tests carried out with a prototype at the Palomar Observatory in California have achieved astrometric resolutions of 100 millionths of an arcsecond, and the improved atmospheric conditions in Hawaii will increase this by a factor of three.

ECONOMIST: A roadmap for planet-hunting

Viewed from ten light-years away, the sun's side-to-side astrometric wobble due to the effect of the earth is just one millionth of an arcsecond, or a twentieth of the tiniest angle that the Keck will be able to measure.

ECONOMIST: A roadmap for planet-hunting