Planet Hunters is a citizen science project to find exoplanets using human eyes.

[1][2] It was launched by a team led by Debra Fischer at Yale University,[3] as part of the Zooniverse project.

On December 14, 2014, the project was re-launched as Planet Hunters 2.0, with an improved website and considering that the volunteers will look at K2 data.

[8] On December 6, 2018, the project Planet Hunters TESS (PHT) was launched and is led by astronomer Nora Eisner.

All exoplanet candidates are manually checked by multiple project members (volunteers and moderators) and need to pass different tests before they are accepted by Nora Eisner and uploaded to ExoFOP.

[17] This candidate was independently detected by Byrant et al. 2023[18] and if confirmed could represent the lowest-mass star to host a close-in giant.

[17] The Planet Hunters project exploits the fact that humans are better at recognising visual patterns than computers.

[19] Periods of reduced brightness can thus provide evidence of planetary transits, but may also be caused by errors in recording, projection, or other phenomena.

[70] In April 2014 the unusually active SU Ursae Majoris-type dwarf nova GALEX J194419.33+491257.0 was discovered.

The unusual light curve of KIC 8462852 (also known as Boyajian's Star)[72] has engendered speculation that an alien civilization's Dyson sphere[73][74] is responsible.

The dips were found by one of the authors, a Planet Hunters participant, in a visual search over five months of the complete Q1-Q17 Kepler light curve archive spanning 201250 target stars.

[77][78] In February 2022 Planet Hunters:TESS announced the discovery of BD+61 2536 (TIC 470710327), a massive hierarchical triple star system.

The system is predicted to undergo multiple phases of mass transfer in the future, and likely end up as a double neutron star gravitational wave progenitor or an exotic Thorne-Zytkow object.