Flat planets?

This is intriguing news.

Am amused by the number of people in comments pointing out Kepler has a selection bias toward detecting multi-planet systems in which the orbital plane is relatively 'flat' compared to our solar system. It certainly does, since the closer planets are to orbiting in the same plane, the better the chance that if one is seen to transit from our perspective, others in the same system will too.

But, the team was expecting to find only a couple of systems where planetary orbits were so closely aligned. So far, they've exceeded that expectation by a factor of 50. That's significant! More than 100 systems with multiple planets observed to transit, when only two or three were expected. Means something new-to-us is going on, because we're seeing a lot more than we expected to even _with_ Kepler's bias toward detecting them.

It is certainly intriguing that these flatter systems have found-planets all sub-Neptune in size. Of course, Kepler wouldn't have detected our Jupiter or Saturn yet, so it may be a bit premature to conclude it's due to a lack of giant planets shaking the systems up. I do wonder if it is true.