It took 11 years, but scientists have now found the earliest known picture of a planet outside our solar system.

Using a new technique that removes starlight from an image, scientists re-examined a Hubble Space Telescope picture taken in 1998 and stripped away starlight to reveal a "hidden" world.

This planet orbits the young star HR 8799, which lies about 130 light-years away in the constellation Pegasus, noted lead study author David Lafrenière of the University of Toronto.

Last September Lafrenière and colleagues announced the first direct picture of an alien planetary system: three massive worlds circling HR 8799. The archived Hubble picture shows the outermost of that planetary trio.

Although the new find is technically confirmation of a previously known planet, the discovery suggests there could be many more unknown planets waiting to be found in Hubble's archives, researchers say.

"They've dug up old Hubble images and found a planet! Crazy!" Geoff Marcy, an astronomer at the University of California, Berkeley, commented by email.

"This will spawn a wild race by astronomers everywhere in the world to dig out their old Hubble images to hunt for planets lost in the rubble of the Hubble."

Stripping Starlight

So far, only a handful of extrasolar planets, or exoplanets, have had their pictures taken directly. Most of the more than 300 known exoplanets have been found based on indirect proof of their existence.

Some are Jupiter-size worlds so massive that their gravity causes light from their parent stars to "wobble."

In other cases, a star's gravitational field magnifies background light like a giant lens. The presence of an orbiting planet periodically adds a tiny amount to this magnification effect.

Still other planets pass in front of their stars as seen from Earth, causing the starlight to dim for a moment.