PH1 : A planet in a four-star system

A family portrait of the PH1 planetary system: The newly discovered planet is depicted in this artist's rendition transiting the larger of the two eclipsing stars it orbits. Off in the distance, well beyond the planet orbit, resides a second pair of stars bound to the planetary system. Image Credit: Haven Giguere/Yale.

Image credit: Haven Giguere/Yale

Today we’re pleased to announce the discovery of the first confirmed planet discovered by Planet Hunters, and it’s a fabulous and unusual world. Labelled ‘Planet Hunters 1’ (or PH1) in a paper released today and submitted to the Astrophysical Journal, it is the first planet in a four-star system. It is a circumbinary planet – one which orbits a double star – and our follow-up observations indicate that there is a second pair of stars approximately 90 billion miles (1000 Astronomical Units) away which are gravitationally bound to the system.

This is much closer than the nearest stars are to the Sun, so anyone viewing the sky from PH1 would have a spectacular view of all four stars. More importantly, this amazing system will help us understand how and where planets can form – producing a stable planet in a system where four different stars are moving about can’t be easy. This is the seventh circumbinary planet, and the first to be in a quadruple system.

The planet itself has a radius a little more than 6 times that of Earth, making it a little bigger than Neptune. It’s mass is harder to pin down (and being in such a complicated system didn’t help), but we have a definite limit that means it must be no more than half that of Jupiter – so this is definitely a planet.

A huge amount of work went into this discovery (as well as a fair bit of observing time on the Keck and other telescopes), but a lot of the credit should be pointed at the Planet Hunters who made the discovery. It was Kian Jek and Robert Gagliano, working together on Talk that made the initial discovery; there’s a post from them on exactly what happened up already. The paper also credits Hans Martin Schwengeler, Dr. Johann Sejpka, and Arvin Joseff Tan all of whom flagged one or more of the transits before the paper was published! This is great news for us and we’re sure there are more planets hiding in data, both at the main interface and over on Talk. For today, though, we can celebrate the arrival of Planet Hunters 1!


PS We’ve announced discoveries before, of course – as well as being the first four-star planetary system, this is the first where we’ve been able to obtain not only transit information but follow up with radial velocity measurements, detecting the wobbles of the parent stars as well as the dips in light seen when the planet moves in front of them. This is the gold standard for planet discovery, and so this is officially a planet, not just a planet candidate.

PPS The paper, of course, still has to be refereed. We’ll keep you updated here as that process goes on, but as Meg is presenting the details of the system at the annual Division of Planetary Sciences meeting right now we thought you’d want to know the news as soon as possible. There will be more posts about exactly how PH1 was tracked down later in the week, so watch this space. In the meantime, you might prefer version of the paper, which has been annotated with the ScienceWISE tool in order to help explain some of the more technical language.


111 responses to “PH1 : A planet in a four-star system”

  1. Michael Hopkins says :

    Ever read “Nightfall” by Isaac Asimov?

    Clearly this planet won’t have perpetual day, but exoplanets only started being discovered in the 1990s. Image what will be found in a 100 years.

  2. Marsha says :

    So exciting! Congratulations! And who is the artist behind that lovely image in this announcement?

  3. Ivy says :

    THis is another awsome discovery. Thanks for sharing this important news with us your fans around the world. Sanlil2012

  4. Andrew says :


  5. daveliz says :

    Maybe we should send politicians there to find what kind of mess they make …

  6. thiyam shivananda singh says :

    How many light year from us? By the way Gr8 job Guys.

  7. Alfred Arrindell says :

    Congratulations on your discovery. What are those black dots?

  8. JoNeZ says :

    This is fine piece of work! Good job! I wonder is there something out there? It would be cool if there could be “humans” or something..I would go there and explore if i would just get chance to get there.

  9. Ro'Vage RavAge St Laurent says :

    If only mankind would unite as one, the way it was in the beginning, we could use our collective consciousness to discover a way to TRAVEL to these places & report what we find with our own eyes……………….
    Unfortunately,we’ll probably end our days in a massive conflagration that will leave no trace that we were ever here in the first place……………….
    “All hail the Imperium of Man”

  10. Mark says :

    Any dinosaurs on this planet?

  11. Alile Kiodes Emmanuel says :

    dis is amazing

  12. Captain Video says :

    If there were also an earth size planet in the habitable zone, the view that any intelligent beings living there would see would be incredibly fascinating. With two suns giving off different color light and two huge stars, a lot bigger than any seen on earth and moving around the sky like our planets, this would be very different from what we experience on earth. It would be great if somebody did a computer simulation of what the sky would look like on such a planet.

    Many years ago I read a science fiction story written by Paul Anderson that described a planet of a double star with different color stars that was fascinating. Among other things as the wind blew the grass in different directions, its color changed. After the larger bluish star set, the planet was lighted by the deep red light of the smaller star until it set.

  13. Charis says :

    this is cool. but where is it in relation to Earth????

  14. Steven Kan says :

    “. . . . anyone viewing the sky from PH1 would have a spectacular view of all four stars.”

    Is there enough data yet to know how “big” the stars would appear from the surface of PH1? Both in terms of angle and magnitude?

  15. Steven Kan says :

    And is there anywhere an animation of the orbits? I’m imaging a really complicated Spirograph :). Remember those?

    • gdmellott says :

      From what I’m able to get from reading and using common logic about the laws of gravity; the two suns which the planet orbits are very close to one another so the common center of gravity as the planet “notes it” does not wobble much. That being the case, the planet’s orbit should be relatively elliptical. Close enough to a single star system to make the discovery reasonably straight forward; though confounded enough by that wobbling center of gravity to make determining the masses involved, by the calculating the Kepler data as one might for single star system, inaccurate.

  16. J R Clark says :

    I wrote a nice little blog about this for you guys and made an awesome infographic detailing a possible orbit style.

  17. Mistylynn says :

    Very exciting!! Congratulations:)

  18. Pallino1021, LLC says :

    Reblogged this on Pallino1021…The Blog and commented:
    An incredible discovery and an ideal example of the importance and power of crowdsourcing!

  19. mbuso scotch Ndlovu says :

    I congratulate the Planet Hunters for their discovery of the PH1. I have a serious concern that the humans that we have here on our mother earth will start to disturb the newly discovered planet. Right now I thihk there are nations which are planning to single handedly occupy the PH1.

  20. Steve C says :

    Brilliant – well done all! Don’t just try for the easy ones! 🙂

    Have linked to this on WUWT’s Tips & Notes to spread the word.

  21. olof lindelöf says :

    I would love to se a diadram of the orbits.

  22. Mike Lopez says :

    That’s a wonder! Does someone know the constellation they are located? Thank you

  23. nic-uk says :

    …”So, yeah, like, I’ve just discovered some treasure somewhere on planet earth, and it’s located near four boulders.”

    What’s the name of the quadruple system???????????

    pretty please 🙂

  24. Ron says :

    How many countries, how many conflicts, how many discoveries, how many wars would fit on this planet?

  25. Bobby says :

    this is awesome, you guys keep looking there’s more out there to find

  26. darshan chandekar says :

    congratulations.. hope to see the real pictures of these planets as our tech. grows and not the artists renderings … cheers..:)

  27. Darnell says :

    great find!

  28. chrislintott says :

    James – the entire Kepler field is in Cygnus, and it’s about 5000 light-years from Earth. The paper that’s linked to in the main article gives all the information you might want, and you’ll have noticed that there is an excellent and growing collection of blog posts giving the background to the discovery too.

  29. Malik Al Hassan Yakubu says :

    These discoveries should make us all admire and hold in awe, the Master Architect of this remarkable universe—- The Almighty God, the Creater of everything that exists; and we thank Him for endowing the human being the intellect to discover His remarkable creation.

  30. Falary says :

    nice job done

  31. SULE. BELLO says :

    Your. new. discovery. of. a planet. with. 4. Suns is. wonderful. and. commendable . I. appreciate. your. effort . From : SULE. BELLO , NIGRIA

  32. meloud says :

    Very exciting!! Congratulations

  33. TLC says :

    Could somebody tell whomever operates the Planet website that Internet Explorer 10 “IS” the latest version of IE . Internet Explorer 10 comes with the Windows 8 64-Bit upgrade… I would like to view their website and all I get is a page saying I need to upgrade my browser…..


  34. PATRICK CASEY says :


  35. aatma tiwari says :

    well,it have been proved, that’s TRUE ie.existance of 4star planet,but it is very difficult to me to realize (understand, digest) it though I’m student of,T.U.Nepal) .is there any way to realize it in 3D space?

  36. Nic says :

    ??? 4 Suns ??? You’d never know what to wear!!

  37. George Kountouris says :

    Is it’s orbit really stable in this environment of complicating forces of gravity?

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