Hubble (plus Gemini and Keck) discovery: three exoplanets directly imaged around star HR 8799, one around Fomalhaut

Ah, so this is the discovery they were talking about last week:

Astronomers have taken what they say are the first-ever direct images of planets outside of our solar system, including a visible-light snapshot of a single-planet system and an infrared picture of a multiple-planet system.

Earth-like worlds might also exist in the three-planet system, but if so they are too dim to photograph. The other newfound planet orbits a star called Fomalhaut, which is visible without the aid of a telescope. It is the 18th brightest star in the sky.

The massive worlds, each much heftier than Jupiter (at least for the three-planet system), could change how astronomers define the term "planet," one planet-hunter said.

That's a total of four planets. Once again the planets themselves aren't that exciting because they're much too large to be an interesting target of possible colonization sometime in the future, but the direct imaging of planets is new which is what is exciting about this discovery. In other words, it's one more step on the way towards acquiring the ability to discover another Earth:

These recent direct images reveal giant, gaseous exoplanets in a new light for the first time, revealing not the effects of the planets but the planets themselves. The next goal would be direct images of an Earth-like planet, the astronomers say.

"The discovery of the HR 8799 system is a crucial step on the road to the ultimate detection of another Earth," Macintosh said.

The problem is that terrestrial (Earth-like) planets are orders of magnitude fainter than the giant Jupiter-like worlds, and they are much closer in to their host stars. That means the glare from the star would be overwhelming with today's technology.

The pay-off could be big, though, as such rocky planets could orbit within their habitable zones (where temperatures would allow the existence of liquid water).

"There is plenty of empty space between Fomalhaut b and the star for other planets to happily reside in stable orbits," Kalas said. "We'll probably have to wait for the James Webb Space Telescope to give us a clear view of the region closer to the star where a planet could host liquid water on the surface."

The James Webb Telescope is to be launched in 2013. Before then we will probably have already discovered Earth-sized planets of course, we just won't be able to directly image them at first.


Edit: Here's an MSNBC video on the discoveries: