Baby Planet Grew Up Quickly

Thanks to good timing, diligent detective work and a little luck, scientists have determined that a suspected bulge in the dusky disk surrounding the nearby star Beta Pictoris contains a giant gas planet, one that formed incredibly fast given the relative youth of its parent star.

Located about 63 light-years from Earth, Beta Pictoris has been around for only about 12 million years, compared to our sun's 4.5 billion years. The star, which is about 75 percent more massive than the sun, sports a bright orbiting cloud of dust and gas. It was the first debris disk to be imaged around another star.

Later studies showed a warp in the disk and comets falling onto the star, observations that suggested the heavy hand of a giant planet's gravity at work.

Astronomers tagged a possible suspect two years ago, but couldn't rule out the possibility that the faint object, seen inside the star's dust disk, was a background star. The image had been taken in 2003, but wasn't identified until astronomers got their hands on a new, more sophisticated analysis tool in 2008.

Follow-up observations in late 2008 and in 2009 showed the object disappearing, then reappearing on the other side of the disk, eliminating the possibility that it was a background star and providing the first data on the planet's size and orbital period.

Because it is relatively close to its parent star -- roughly about where Saturn orbits in our solar system -- astronomers believe the object is a home-grown planet, not a captured brown dwarf star or another type of object captured from a sibling star. The planet, christened Beta Pictoris b, has about nine times the mass of Jupiter and is the right size to explain the warp seen earlier in star's dust disk.

"We've tried before but we've never had a case where we could link a real planet with a real structure in the disk. We can now see a planet and a structure together, so I think this is something that will be receiving much more attention," Dániel Apai, with the Space Telescope Science Institute in Maryland, told Discovery News.

Among the few planets beyond the solar system that have been imaged, Beta Pictoris b is the closest to its parent star, added lead astronomer Anne-Marie Lagrange, with the Laboratoire d'Astrophysique de l'Observatoire de Grenoble in France.

Follow-up studies are planned to refine the planet's orbit, to look for sibling planets and to attempt to tease out information about the planet's atmosphere.

Astronomers believe Beta Pictoris b is finished growing, with little gas left in the star's disk for planet-forming. Rocky body planets, like Mercury, Venus, Earth and Mars, however, may still be works in progress.

The research will be published in this week's issue of Science.