Michael Kieran

Technology, imaging, and more.

Community of Amateurs Discovers Planets Around Other Stars

LLOri-hubble-4806 Nebula

One of the most interesting communities on the web reached a significant milestone last month, when Zooniverse.org announced it now has more than a million registered volunteers – citizen scientists contributing to dozens of projects from astronomy to zoology.

The community started seven years ago with the Galaxy Zoo website, where volunteers help professional astronomers by looking at pictures of galaxies and classifying them according to their overall shape and the presence of spiral arms. Since then Zooniverse has expanded to include websites devoted to a variety of scientific disciplines. You can classify animals caught in camera traps on the Serengeti plains in Africa, help marine researchers understand what whales are saying, or transcribe historical ship logs to help build better climate models.

Zooniverse and other citizen science web sites tap into the innate human ability to recognize patterns among complex data sets, such as figures or structures in a photographic image. But they also benefit from the basic human need to belong to a community. And unlike the work of a single scientist, a large online community can combine the independent assessments of many non-experts, thereby gaining the “wisdom of crowds” in which the group opinion is equal to or better than that of any one expert (or the best computer algorithms currently available).

Screen shot of PlanetHunters.org  web site, with dialog box asking the user to mark visible transits.

Adding to the world’s scientific knowledge is as easy as looking at graphs and drawing little boxes around outlying points.

PlanetHunters.org is one of the Zooniverse’s most successful projects – a site where anyone can view the light curves captured by the Kepler space telescope to identify possible exoplanets – planets around stars other than our sun. Launched in 2009, Kepler spent four years looking at one small patch of the sky, staring at the same 160,000 stars in order to detect tiny decreases in brightness, caused by transits as the exoplanet passed in front of its sun. We’re talking very, very subtle decreases here, equivalent to a pinhead moving in front of a distant car’s headlight.*

To get started on PlanetHunters, you just sign up and watch a two-minute tutorial video, then click Start Hunting for Planets. You’re presented with a light curve for a star, and asked identify its overall pattern as either variable, quiet, or don’t know. Then you’re asked if the star shows any transit features (i.e.: dips in brightness caused by a planet), and if so to draw a box around them. That’s all it takes.

The PlanetHunters website makes it super easy for people to engage with others in their growing community:

  • They maintain an interesting blog, have an active presence on Facebook (137,000+ followers) and Twitter (8,000+ followers), and sponsor occasional meet-ups in the real world;
  • Each time you finish reviewing a star system’s light curve, a pop-up asks whether you’d like to discuss the object, and links to an online forum where you can review and discuss it with other community members;
  • The forum also highlights Recent Objects and Trending Objects, and these have become popular meeting places where you can watch in real-time as amateur and professional astronomers discuss the meaning of the latest results.

When a star is flagged by five or more people, the Kepler astronomers analyze it further. PlanetHunters volunteers have already discovered two confirmed exoplanets, with more than 30 additional discoveries currently under review.

NASA artwork of four-star system

Amateur astronomers combing through data from the Kepler orbiting telescope discovered a planet in a four-star system similar to this. Illustration Credit: NASA/JPL-Caltech/T. Pyle (SSC)

The biggest discovery so far is by Robert Gagliano of Cottonwood, AZ and Kian Jek of San Francisco, CA, who together identified an unusual shape in the curve of an eclipsing binary system (two stars in close orbit around one another) called KIC4862625. The planet they found, now called PH1b, is a little larger than Saturn, and transits across the larger star every 128 days. Further analysis and observations revealed that another binary pair of stars orbit PH1b’s main binary system, making it the first quadruple-star system to host a planet. That’s a pretty impressive scientific advance for a user community, especially one composed mainly of “amateurs”.


* The pointing mechanism on Kepler recently suffered two component failures, forcing NASA to halt the orbiting telescope’s observational program; engineers are now testing a fix that would enable the scope to observe different areas of the sky for shorter durations. Even in the worst-case scenario, if Kepler were completely disabled, astronomers would still have years of work ahead, mining the rich trove of data it’s already captured.


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