It never ceases to amaze me what information we can glean about things so far away from us. Zach Berta in the article is my friend, so it's neat to see this ar

It never ceases to amaze me what information we can glean about things so far away from us. Zach Berta in the article is my friend, so it's neat to see this article here on HN. :-) When the article was accepted for publication we all watched Waterworld and he gave a high level overview of the research to me (as a non-astrophysicist). How I understood it is: When the orbiting planet crosses between its star and us, it blocks some of the light, and the decrease in brightness can be used to calculate the diameter of the planet. In addition, the planet orbiting the star makes it wobble a bit, and from that you can calculate its mass. These two things limit the possibilities of the planet's composition, and a watergiant is the most likely scenario. In the papers on the Arxiv[1], it looks like there's finer grained observations than those, though, so maybe that was just what caused them to give it a closer look. [1] http://arxiv.org/find/all/1/all:+AND+berta+gj1214b/0/1/0/all/0/1 http://arxiv.org/find/all/1/all:+AND+berta+gj1214b/0/1/0/all...