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As Planet Hunters participants sort through the brightness data in the form of graphs of brightness vs time (known as light curves), they notice different patterns of variability. Much of the variability (on timescales of hours to days) may be caused by starspots or pulsations of different types of variable stars. Having Planet Hunters sort families of similar light curves is part of the important scientific research.

Participants in Planet Hunters ( look at changes in star brightness using data collected by NASA's Kepler spacecraft, which has exquisite and unprecedented precision in detecting changes in brightness (photometry).

Update 2013 March 22: Planet Hunters is looking for US-based 6th-8th grade science teachers. If you're a teacher, we need your help to test and evaluate lessons from our new Planet Hunters Educators Guide in your classroom this spring. If you're interested please email with your name, grades taught, and location.
--Kelly and the Zooniverse Education Team.
Update 2013 Jan 7: A Newly Confirmed Planet and 42 Additional Planet Candidates. We are pleased to announce the discovery and confirmation of our second confirmed planet : PH2 b-a Jupiter-size planet in the habitable zone of a star like the Sun-by the Planet Hunter project. The paper has already been submitted to the Astrophysical Journal

The Kepler team developed computer programs to sift through light curve data because it is not possible for them to visually inspect every light curve. Planet Hunters are betting that there will be a number of surprises in the data that the computer algorithms will miss; that that there will be planets which can only be found via the remarkable human ability for pattern recognition. The human brain is particularly good at discerning patterns or aberrations and experiments have shown that when many people work together, the collective wisdom of the crowds can be better than an expert. Planet Hunters is an online experiment that taps into the power of human pattern recognition. Participants are partners with our science team, who will analyze group assessments, obtain follow up observations at the telescope to understand the new classification schemes for different families of light curves, identify oddities, and verify transit signals.

The Kepler spacecraft beams data for more than 150,000 stars to Earth at regular intervals. With every download of data, the time baseline of the light curves is extended. The light curves are being released into the public archive at to encourage broader participation and we think that the public can play an important as our scientific partners in this latest Zooniverse project.