β Pictoris is a nearby young star that weighs in at about 1.75 solar masses and is surrounded by a disk of dust and gas that we see nearly edge-on from Earth. In 2003, images in the near infrared band identified a faint, point-like object about 8 astronomical units (an AU is the distance from the Earth to the Sun) away from the star. The observation was not sufficient to determine if this source was gravitationally bound to β Pictoris, or just some random background star sneaking in to the image.

Subsequent observations, made in early 2009, failed to turn up this companion object. However, high-resolution observations taken later that year using the European Southern Observatory’s Very Large Telescope’s Adaptive Optics NaCo instrument revealed a faint point source comparable to the one noticed in 2003. This indicates that it's not a background star, but a gravitationally bound companion—a planet orbiting within β Pictoris' disk of gas and dust.

The current edition of ScienceExpress contains a paper from French and German researchers in which they consider the implications of this find. They plugged the age of the star, its distance from Earth, and the apparent brightness of the planet into a widely used planetary evolution model, which calculated that the planet weighs in at 9±3 Jovian masses. Measurements of its orbit give it an orbital period of 17 to 35 years at an orbital distance from β Pictoris between 8 and 13 AU. In terms of our Solar System, the planet would be orbiting the Sun somewhere around Uranus and Neptune.

The mass suggests that this is a gas giant that formed from a non-rotating cloud of hot gas that contracted as it cooled. The surprising thing about this planet is the time scale on which it must have formed. With the host star only about 10 million years old, it must have formed in only a couple of million years, much faster than previous expectations. This work also offers up a new potential methodology for detecting exoplanets: looking for deformations in the gas-rich disks that exist around young stars.

ScienceExpress, 2010. DOI: 10.1126/science.1187187 (About DOIs).