Note from Lee: Video is best viewed in HD, full-screen mode.
Following up on yesterday's post about Dan Fabrycky's festive rendition of Kepler's candidate multi-planet systems, I'm proud to unveil an exclusive new visualization of Kepler's candidate planets, courtesy of the multitalented Jer Thorp, who has an excellent blog at blprnt.blg.
Jer is a native of Vancouver, Canada, but he currently makes his home in New York City, where he is the New York Times' Data Artist in Residence and a visiting professor at New York University. He's also a contributing editor at Wired UK. Shortly after the Kepler data release, Jer and I started talking about how he could dynamically visualize both the magnitude and the nuance of the discoveries. This is what we came up with.
What you're looking at is every Kepler candidate, arranged as if orbiting a single star. In the real world, this would result in a catastrophic gravitational destruction derby, but in our virtual world it simply normalizes the candidates and allows a proper sense of scale to be perceived. Each candidate's estimated size, orbital speed, and orbital separation is accurately depicted, and each world is color-coded according to its estimated effective temperature, with red being relatively hot and deep blue/violet being relatively cold. Mercury, Mars, Earth, and Jupiter are added for context; the high-value Kepler candidates KOI 326.01 and 314.02 are also highlighted.
The color scale is calibrated so that Earth is a pale blue dot. This is the color it would display across the gulfs of interstellar space, a hue that suggests blue oxygen-rich skies and deep liquid-water oceans. Two concentric rings plot distances of 0.5 and 1 astronomical units from the central star, and a pale blue line delineates Earth's location on two self-organizing charts. In the video posted above, the first chart in the sequence plots semi-major axis (i.e., average orbital separation) versus effective temperature, while the second plots semi-major axis versus planetary size.
Important data trends prominently emerge from this visualization. The abundance of smaller candidates and relative sparsity of larger ones clearly indicates that there are many tiny, meek worlds for every giant planet. But curiously there is a relatively stark drop-off in the frequency of Kepler candidates at or below approximately Earth-size. My gut says this is probably an observational bias that later data releases will smooth out, but perhaps it's not, and Mother Nature actually prefers slightly chubbier planetary progeny, with Earth being a slender outlier.
Similarly, Kepler's nascent sensitivity to smaller planets with larger orbital separations is also suggested from the pile up of small, hot, fast-moving planets in very short-period orbits. The tight clustering of worlds large and small, cold and hot, all well within the orbit of Mercury testifies to the fact that most of Kepler's haul thus far comes from small, cool stars. Only later data releases will probe the habitable zones of larger, hotter stars like our Sun. Hopefully, the best is yet to come.
The visualization also highlights some things that are just plain weird. For instance, several other apparently promising candidates accompany both KOI 326.01 and 314.02 in terms of estimated habitability. Why weren't they assigned higher values based on Greg Laughlin's equation? I'm guessing part of the answer is that they orbit very distant and dim stars that offer extremely marginal chances of follow-up observations, something that Laughlin's formula substantially penalizes. The rest can be explained by the fact that any candidate large enough to be easily noticeable in this visualization is several times the size of the Earth, and hence of dubious habitability. The prevalence of apparently promising pale blue dots is an artifact of just how great the disparity is between the largest and smallest candidates.
Speaking of which, the largest candidate, an enormous pale blue orb, strikes me as extremely strange. It's several times larger than our solar system's heavyweight champion, Jupiter, yet it's also relatively distant from its star, and estimated to be rather cool. If I recall correctly, planets puffed-up to such large sizes get that way through being extremely hot and close to their stars. Perhaps this candidate will turn out to be something distinctly unplanetary, like a brown dwarf.
What do you see in this visualization? Do any clarifying insights or unsolved puzzles leap out at you?
How do you think it could be improved?
Let me know in the comments, and stay tuned—there may be an updated, interactive version of this coming soon.