Yesterday, astronomers announced the discovery of a compact solar system orbiting a distant star, with two of the planets being very close to the size of the Earth.
My friend Fraser Cain, from Universe Today, put together a video chat Q&A about the discovery with me, Nancy Atkinson from UT, Emily Lakdawalla from the Planetary Society Blog, and Alan Boyle from the MSNBC Cosmic Log blog. We talked about the discovery, how it was made, what it means for exoplanetary science, and a few other topics just for good measure.
Fraser did this using Google+ Hangout, the social network’s video chat software. They rolled out a new feature just a few days ago where a few people can chat on camera, and the whole thing can be broadcast on G+ at the same time. Not only that, but, obviously, it can be recorded and uploaded to YouTube as well. This is brand new stuff, and not widely available just yet, so we had some issues with it (notably Fraser’s window never was displayed on the main screen; the images he displays at 13 minutes in can be found on the Kepler website).
Since I’ve got you here, there’s one very cool thing I’d like to expand on. Later in the video, we chatted about the physical characteristics of the Kepler-20 system, including how the planets’ orbits were tilted, and how you can determine that from the Kepler data. I poked around on the web afterwards, and found that the Kepler site has an amazing feature; an interactive display of all the confirmed planets they’ve found. For example, here’s the one for Kepler-20-f, the outermost of the five planets in the system, and the one closest to the size of Earth.
You can watch an animation of it going around the star, with a display of how it blocks the light. You can also see how the orbit is slightly tilted to the line of sight, and how it cuts a chord across the star. It’s truly a splendid way to show folks what they’ve found, and I highly suggest playing around with it (though it may be slow due to heavy use right now). When it loads, click the button labeled "Perspective" and then click "go to view from Earth". That’ll show you how a transit works pretty well.
From those pages, I found that these planets do orbit their star almost — but not quite — edge-on. An orbital inclination of 90° would be edge-on, and the planets, in order from the star, have tilts of 86.5, 88.4, 89.6, 87.5, and 88.7°. I was surprised to see that there is a spread of even as much as 3°. I wonder why? The planets probably formed farther out and migrated in toward the star; we know planetary migration happens for many (if not all) solar systems when they’re young, including our own. As these planets got closer, they could interact more strongly via gravity. Maybe that amplified their tilts somewhat. Or maybe I’m totally wrong in thinking the tilts should all be aligned in the first place.
We’re still new at this game, so there’s a lot left to learn. But that, my friends, is where the fun is. May we have lots more fun systems like Kepler-20 to investigate.