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 http://exoplanetarchive.ipac.caltech.edu/index.html and includes links to documentation for all these services.

The project’s second confirmed planet, PH2-b (a Jupiter-sized gas giant planet orbiting a Sun-like star), was discovered by several members of the PH community who classified the light curve and then posted the candidate on Talk. A volunteer-organized effort took this from a possible repeat of transits to a likely candidate that was then passed to the Science Team and subsequently validated as a real bona fided planet. Volunteer rafcioo28 who was the first person to mark a transit in Q4. Mike  Chopin was the second and the one to first  post on the Talk page about the transit in February of last year. Hans Martin Schwengeler went to look at the rest of the publicly released Kepler data months later spotting the other transits. Together rafcioo28, Mike, and Hans with the help of Abe Hoekstra, Tom Jacobs, Kian Jek, Daryll LaCourse  have discovered Planet Hunters’ 2nd confirmed planet PH2-b.  I’ve asked Mike and Hans (rafcioo28 we haven’t been able to contact thus far) write a bit about their thoughts on the discovery.

Artistic rendition is a hybrid photo-illustration, showing a sunset view
from the perspective of an imagined Earthlike moon orbiting the giant planet, PH2 b. Image Credit: H. Giguere, M. Giguere/Yale University

Mike Chopin

At school, at the age of fourteen, I did a project on atomic (particle) physics which gained me a grade 1 CSE. The following year I studied and passed my Physics exam which was interesting for my school since that was a subject not on the school curriculum. After leaving school, I studied OND Engineering at Kingston Polytechnic although I only completed my first year since I longed to go travelling. My wanderlust got the better of me and I joined a shipping line as a Navigating Cadet Officer. I suppose it’s easy to see why astronomy has fascinated me since knowing about stars was part of my navigation syllabus.

My childhood hero was, and still is, Captain James Cook a man I consider to be the greatest explorer of all time. I consider myself fortunate to have visited many places this great navigator charted. In 2012 his observation of the transit of Venus in 1769 was commemorated at Venus Point in Tahiti. Although I wasn’t there for 2012, I did get to Venus Point a couple of years earlier. Like Cook, I spent some time in the Navy and have a passion for boats especially under sail. I have two complete circumnavigations under my belt; the first by sea (unfortunately via the Panama Canal and not Cape Horn) the second was by air, island hopping my way across the Pacific. I have now visited ninety six countries and hope that it won’t be too long before I join the Travellers’ Century Club.

Latterly, I was employed by Lloyds TSB (Registrars) as a project officer with my principal role as the sole technical writer writing context sensitive help for software, on-line documentation, trouble-shooting guides for the IT department and interactive eLearning modules. Following redundancy, I went freelance as a writer and have had a couple of small contracts both as a writer and as a data manager.

I am delighted to have been involved with the discovery of an exoplanet, a planet orbiting a distant sun. From the outset, I enjoyed the thrill of analysing the light signals recorded and posted on the planethunters.org website. This website invites ordinary people to take part in analysis of vast amounts of data. Often called ‘Citizen Science’ this excellent website provides clear tutorials to enable the amateur to partake in this worthwhile research project.

In its simplest form, when an exoplanet passes between our line of sight and its sun, there is a reduction in the amount of light that we receive. This effect can be seen if we plot the light output from this star against time. While trying to analyse the data, I would try to imagine the planet transiting its sun, if it was a large planet and close to its sun would it cut more light than if it had been a small planet and a giant sun? Does it have a high reflectivity (albedo) and is it inclined to its ecliptic and if so, would it add or reduce the amount of light recorded. If distant suns had multiple planets with systems similar to our own solar system, then would it be possible to identify additional planets. It was with all these ideas in mind that I began my quest for the exoplanets.

Sometimes, the pattern appeared to be too random to be able to distinguish a planet and at others, beautiful patterns could be seen as if generated by an oscilloscope, these it would seem were possible candidates for a binary star and so these were recorded also. Now and again, a pattern would emerge which would make you sit up and take notice. Using the sliders on the screen, I would drag out the ‘x’ scale to magnify a section of the screen where I was certain a transit was occurring and then I would check to see whether there was a second transit which may indicate its periodicity. It was during such an event that I found, what is recently been called, PH2-b. With, what at time was simply a planetary candidate; I posted a note to see if any of my fellow planet hunters had seen what I had seen.

Carl Sagan spoke of the ‘Pale Blue Dot’, the Earth as seen from Voyager 1 in the distant reaches of space, how exciting would it be if spectral analysis revealed this planet to have water and an atmosphere, another ‘Pale Blue dot’, now that would be truly remarkable.

Hans Martin Schwengeler

I’m a regular user (zoo3hans) on PH, more or less from the beginning two years ago. My name is Hans Martin Schwengeler and I live near Basel in Switzerland. I’m 54 years old, I’m married and we have two children. I’m a mathematician and work as a computer professional. I like to advance Science in general and Astronomy in particular. I did work a few years at the Astronomical Institute of the University of Basel (before it got closed because they decided to save some money…), mainly on Cepheids and the Hubble Constant (together with Prof. G.A. Tammann). Nowadays I’m very interested in exoplanets and spend every free minute on PH.

I’ve always been interested in stars, planets and the universe in general. So when I studied Mathematics at the ETH in Zurich it was natural to choose Astronomy as a second discipline. After working a few years on a Statistics research program (based on the Kalman Filter) I managed to get a job at the Astronomical Institute of the University of Basel (Switzerland) as a system manager. There I could work part time on research programs, mainly on Cepheids to determine the Hubble Constant (together with G.A.Tammann and Allan Sandage). I did this with the image processing software ESO-MIDAS, where we analyzed images taken by the ESO New Technology Telescope (NTT) or the Hubble Space Telescope (HST). I also used a program (written in Fortran-77) called superperiod to find the periods of the variable stars found in the galaxy images and see if they could be cepheids with periods between 2 and 100 days. With the Cepheid period-luminosity relationship we were then able to determine the distance of the Cepheid and the host-galaxy.

As soon as Michel Mayor and Didier Queloz detected the planet around 51 Pegasi, I was drawn in into exoplanets. I followed every single announcement of the detection of a new exoplanet on Exoplanet.eu and arXiv.org and elsewhere. So when I first took notice of the Planet Hunters project, I joined immediately. In the meantime the Astronomical Institute has been closed down (on monetary reasons) and I was working as a systems engineer at the Federal Office for Information Technologies and Telecommunications in Bern. I did not have anymore the tools needed to analyze light curves and so on. I also had to realize that to detect a planet transit in a Kepler light curve is not so easy as I first thought (except for the very big Jupiter-like ones). The learning curve was rather steep. Fortunately some fellow hunters had already gathered some very good insight and also some useful tools. So after some months I think I accumulated enough experience to do some real work here on PH.

So when I got the light curve for KID 12735740 I thought it looks very nice and might be a real planetary transit. Kian Jek had already commented on it favorably. The transit shape is more like an “U” instead of a “V”, the transit depth and duration is compatible with a 1.1 R_Jupiter planet with a period around 282.6 days. We can check this with Kian’s very good Planetary Calculator. The first thing I then usually do, is to have a look at the sky view  and then post this image to the PH Talk pages for others to have a look too My second step is then to download the FITS files from MAST (using the very good tools from http://www.kianjin.com/kepler/detrend.tar.gz ), detrend the curve roughly and view it by eye first (often using the program ggobi for this purpose). I upload the light curve also to PH if it looks interesting. Thirdly I may do a periodogram to find the period if a good period seems to be present (and upload it as well of course).

In the case of KID 12735740 I think all looks very good for a real planet candidate. Not much would be possible without the help of others, especially Kian Jek (aka kianjin) is invaluable here at PH. He compiles very good lists of “good candidates” or EB lists. I also find the other lists of “good Q2 candidates (non Kepler favorites)” (or Q3, Q4, etc. lists) very helpful in finding candidates and discuss them in more detail. It’s otherwise rather difficult to keep track of all the interesting cases on PH Talk. Kian does also the best detrending jobs, contamination vector determination, fitting of transit parameters, and more. nighthawk_black does perfect Keppix analysis, troyw has his amazing AKO service, capella, JKD, ajebson, gccgg, Tom128 and many other are very helpful too.So very often we work together here at PH as a good team.

In order to discriminate between real transits and instrumental or processing artifacts, I add comments to the “consolidated list of glitches” in the Science section on the PH Talk site. I collected a few bright and quiet and constant stars over the last few months / years exactly for this purpose. When I see a dip on one light curve and the same feature is also present on the other light curves, then it’s very likely a glitch.

I think the PH project is a great contribution to Science. I’d like to thank all fellow PH hunters for their help and also to Meg.

Kind regards,
Hans Martin Schwengeler (aka zoo3hans)

—

In addition to Mike, Hans, and rafcioo28, several others get a tip of the hat for marking transits in the discovery light curve for PH2: Sean Flanagan, Anand, and Jaroslav Pešek. Congratulations to you as well.