PH1 Paper Offically Accepted for Publication

Last October we announced the discovery of PH1 – a four star planetary system hosting a circumbinary planet (PH1b). The transits were spotted by volunteers Robert Gagliano and Kian Jek  on Talk. I’m thrilled to announce that our paper “Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System” has been officially accepted to Astrophysical Journal. Congratulations to all involved.

Now that the paper has been accepted and is in press, you can find the accepted manuscript online and added to the Zooniverse publications page (which has a total of 4 Planet Hunters in press/published papers based on your clicks). The official journal version will be published sometime in May.

PH1b is our first confirmed exoplanet discovery, a milestone for Planet Hunters. The 6.18 Earth radii planet orbits outside the 20-day orbit of an eclipsing binary consisting of an F dwarf ( 1.734 x the Radius of the Sun) and M dwarf ( 0.378 x the Radius of the Sun). For the planet, we find an upper mass limit of 169 Earth masses (0.531 Jupiter masses) at the 99.7% confidence level. With a radius and mass less than that of Jupiter, PH1b is a bona fide planet. Not all planet candidates can be confirmed as we could with PH1b. Since PH1b is orbiting an eclipsing binary, we could use the fact that there are no changes in the timing of the stellar eclipses due to the planet to constrain PH1b’s mass.

With the acceptance of the paper, we have asked that PH1b be added to the NASA Exoplanet Archive (NExSci)’s  list of confirmed exoplanets . NExSci has taken on the role of being the keeper of the list of confirmed exoplanet discoveries. In addition, PH1b has bestowed the Kepler # that was saved for us in October. PH1b has been given officially a Kepler designation of Kepler-64b and added to the list of planets in the Kepler field. You can find out more about what the criteria for obtaining a Kepler # is here.

In the list of confirmed planets, the planet is referred to as PH1b (you might notice an extra space – that should be revised in an update to the NASA Exoplanet Archive). I like to think of the Kepler # as icing on the cake. We’ll still refer to the planet as PH1b. Kepler-64b will be an alternate designation and used in the catalog of planets in the Kepler field (PH1b will be listed as an alternative designation). The full data page for PH1b on the NASA Exoplanet Archive can be found here

For those who are wondering what the NASA Exoplanet Archive  is, Rachel Akeson, Deputy Director of NexSci and Project Scientist for the NASA Exoplanet Archive, explains below:

The NASA Exoplanet Archive is an online astronomical exoplanet and stellar catalog and data service provided to the astronomical community to assist in the search for and characterization of exoplanets and their host stars.

Current data content and tools include:

  • Interactive tables of confirmed planets, Kepler Objects of Interest (which includes the planet candidates), Kepler Threshold Crossing Events, stellar parameters for all Kepler targets in Q1-12 and a list of Kepler confirmed planet names and aliases.
  • Overview pages with all available data for each confirmed planet and Kepler Object of Interest
  • Tools to view, normalize, phase and calculate periodograms for light curves, particularly those from Kepler and CoRoT
  • Transit predictions for all known transiting planets and Kepler Objects of Interest
  • URL-based access to all table data

The archive is available at and includes links to documentation for all these services.


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