Reply #4: link to the journal article

[Bill McBlueState]

Here's the preprint of their article: http://xxx.lanl.gov/abs/astro-ph/0609369

The new planet was discovered by transit photometry, meaning astronomers observed small dips in the brightness of its parent star in order to infer its existence. This is different from the way most planets are found. The more common method involves noting minute changes in the velocity of the parent star as the planet tugs it back and forth. The advantage to transit photometry is that it gives you an unambiguous determination of the planet's mass and radius. The more common radial velocity method gives you only a lower limit to the mass.

So the claim "largest known planet" is actually a little misleading. Of the dozen or so planets discovered by transit photometry, this one has the largest radius. But some of the planets discovered with the other method likely have larger radii; we just don't know them yet.