Celestia Forums

Detection of transits of the nearby hot Neptune GJ 436 b. This is the first known transiting hot Neptune.

According to radius/structure models, the planet is mostly composed of water, with a hydrogen/helium envelope, so the planet is similar in structure to the ice giants of our solar system, rather than being a super-Earth or a mini-Jupiter.

More info at systemic.

Hot Neptune, eh? I bet they are common; even GL581c might be a baby-hot-Neptune.

This suggests that water is very common in planets outside the solar system, and perhaps ocean planets are everywhere.