Reanalysis of images taken in 1998 by the Hubble Space Telescope, has uncovered visual evidence for 2 exoplanets that went undetected back then.

Finding these hidden gems in the Hubble archive gives astronomers an invaluable time machine for comparing much earlier planet orbital motion data to more recent observations. It also demonstrates a novel approach for planet hunting in archival Hubble data.

By finding the planets in multiple images spaced over years of time, the orbits of the planets can be tracked. Knowing the orbits is critical to understanding the behavior of multiple-planet systems because massive planets can perturb each other's orbits.

"From the Hubble images we can determine the shape of their orbits, which brings insight into the system stability, planet masses and eccentricities, and also the inclination of the system," said Remi Soummer of the Space Telescope Science Institute, part of a program administered by the California Institute of Technology.

Soummer next plans to analyze approximately 400 other stars in the archive with the same technique, improving image quality by a factor of 10 over the imaging methods used when the data were obtained.

"We wanted to revisit surveys taken of young, nearby stars, as these are prime targets for imaging exoplanets," says Laurent Pueyo, a NASA Sagan Fellow working with Soummer. "Stars with evidence of circumstellar dust will also be good targets, as this is commonly linked with planet formation."

Source: http://hubblesite.org/newscenter/archive/releases/2011/29/ .