Wednesday, January 13, 2016

Asteroid families

Another d3.js goodie: Asteroid families grouped by proper orbital elements semimajor axis (ap), eccentricity (ep), and the sine of inclination (sin ip). They are color-coded by color indices (i.e. not natural colors) derived from the SDSS moving object catalog, which are indicative of composition. The visible grouping of dots in similar orbits and similar colors therefore, the reasoning goes, show physical asteroid families that share a common origin. For the precise definition see the GitHub repository.

Rotate with mouse or fingertip, zoom in/out with mouse wheel or gesture, whatever your device supports.

This plot was originally inspired by this post on Emily Lakdawalla's Planetary Society blog, showing the static versions of this plot. They are by all means amazing illustrations of the family relations in the asteroid belt, but to show the relations in the domains of three proper elements requieres three different plots. So I was thinking, is there a way to display all three of them in one diagram? And with my recently acquired skill in making interactive star maps I thought I'll give it a try and came up with this thing. A revolvable display cube that can show the coordinate space from all directions and zoom in or out.

I also finally learned how to make d3.js display lots of elements efficiently: with HTML5 canvas. I still had to restrict the data to asteroids brighter than H = 14 absolute magnitude to make the display sufficiently responsive. To see the full data (>6MB), clone the repository or download the tarball and change the datafile from 'ast-proper14.csv' to 'ast-proper.csv' and see the full monte. Warning: very slow, only do this at home!

Anyway, the canvas acceleration and other tidbits I've learned should have repercussions for all my other d3 projects. Also thanks to Emily Lakdawalla and Alex Parker, who did the original research, for the great work.

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