Direct Observation Very difficult because the star is very bright and the planet faint. May Detect Planets Better Planets are much cooler than the stars so their spectrum peaks in the infrared. Angular resolution of telescopes not as good in the infrared. Can see much fainter objects in the visual. Interferometers - provide high spatial resolution.
Infrared measurements are much better when done from space.
Programs are being considered which combine the two. Earth-like planets pass in front of the star. Difficult because large numbers of stars need to be monitored. Gravitational microlensing is the only way to search for isolated, planetary-mass objects. As the planet moves around the star, the star has a reflex motion .