back to article Astroboffins may have found the first exomoon lurking beyond the Solar System

Scientists have spotted what may be the first Moon to be discovered outside the Solar System, according to a paper published in the journal Science Advances on Wednesday. Finding exoplanets is a difficult task, let alone exomoons. David Kipping, assistant professor at Columbia University, has kept at it for almost a decade. …

  1. Mark 85 Silver badge

    Serious question for the star gazers.

    The one thing I don't understand in this, is Earth takes a year to orbit the Sun. Assume a similar situation "out there". Do the boffins watch a given star for a long time or just randomly say every couple of weeks/months?

    1. LDS Silver badge

      Re: Serious question for the star gazers.

      Kepler kept on looking at the same stars for a long period. Once a candidate is identified, it can be monitored using other instruments. Still, this type of observation can skew the data towards planet with shorter periods of revolution - Jupiter with its 12 yrs period would be hard to catch - and they have to pass in front of their star seen from here, while transits may last a few hours only. A good thing is CCDs allow for "metering" several stars at once within the field of view.

      1. teebie

        Re: Serious question for the star gazers.

        Which is why the first exoplanets discovered were massive, fast an close to their stars. 'Superearths' and further away planets are mainly more recent discoveries.

    2. pɹɐʍoɔ snoɯʎuouɐ

      Re: Serious question for the star gazers.

      Do the boffins watch a given star for a long time or just randomly say every couple of weeks/months?

      they record data continuously over a long period time at section of space, then they trawl through that data looking at the intensity of the stars. they look for dips in intensity and for repetition of them. large short period planets show up first, but over time they find the smaller and multiple planets, and now moons....

      its takes more years to study the data than it does to record it....

  2. Anonymous Coward
    Anonymous Coward

    The researchers hope that details might be confirmed when NASA finally sends the James Webb Space Telescope to space and its powerful enough to see if its a moon or not

    I am looking forward to the message back from the telescope:

    "That's no moon"

    1. wolfetone Silver badge

      I am looking forward to the message back from NASA:

      "We're going to need a bigger boat"

      1. TheProf

        You just wouldn't let it lie.

    2. LDS Silver badge

      "That's no moon"

      Well, when it's blown up it should be easy to see on the IR sensors of Webb...

      1. onefang Silver badge

        Re: "That's no moon"

        I have a bad feeling about this.

    3. Toni the terrible

      That is a moon

      Obviously Endor, watch out for furry midgets

      1. vir

        Re: That is a moon

        Endor's forest moon, I believe you mean.

      2. Michael Wojcik Silver badge

        Re: That is a moon

        watch out for furry midgets

        Definitely, because the Ewoks are the most dangerous species in the Star Wars universe.

    4. Michael Wojcik Silver badge

      I am looking forward to the message back from the telescope:

      "That's no moon"

      [Paul Hogan voice] That's a moon!

  3. Michael H.F. Wilkinson Silver badge
    Thumb Up

    Exciting stuff

    Great boffinry! Fingers crossed for successful follow-up observations

  4. Aladdin Sane Silver badge

    As always, this---->

  5. arctic_haze Silver badge

    Moons of the moons?

    Isn't it like fleas in the famous Jonathan Swift poem?

    "So, naturalists observe, a flea

    Has smaller fleas that on him prey;

    And these have smaller still to bite 'em,

    And so proceed ad infinitum.

    Thus every poet in his kind

    Is bit by him that comes behind. "

    1. Primus Secundus Tertius Silver badge

      Re: Moons of the moons?

      Big moons have little moons

      That can be seen to orbit 'em

      And little moons have lesser moons

      And so ad infinitum.

      1. Anonymous Custard Silver badge

        Re: Moons of the moons?

        So it's moons all the way down, or depending on your viewpoint, around...

      2. Robert Helpmann?? Silver badge

        Re: Moons of the moons?

        Great! Now we have another category of celestial body the IAU currently has no definition or even name for and will screw up when they get 'round to it. Allow me to be the first to propose exosubmoonlets (extrahyposatellites had too many syllables) defined as an object that orbits a moon1 such that the center of the orbital system is inside the mass of the moon.2

        1. Moon: [proposed] An object that orbits a planet3 such that the center of the orbital system is inside the mass of the planet.

        2. If the center of an orbital system is outside the mass of its members, they are in a committed relationship, binary or otherwise. This leads to the possibility of coexosubmoonlets which is very exciting and will probably have a small, militant and vocal online presence any day now.

        3. Planet [proposed] A non-stellar object orbiting one or more stellar objects but not orbiting another object as well. Note: Planets come in many sizes, shapes and colors and should not be judged or discriminated against because of this; they are all still planets.

        1. Aladdin Sane Silver badge

          Re: Moons of the moons?

          Where does Jupiter fit in this definition?

      3. ghp

        Re: Moons of the moons?

        You maybe swift, but not Swift. It only rhymes on paper (so to speak). :-(

  6. DougS Silver badge

    With a moon that large

    The moons of the moon might be earth sized, so if theoretically one was habitable that would make for some pretty impressive (and quite frequent) eclipses!

    1. John Mangan

      Re: With a moon that large

      ....not to mention 'interesting' tides.


      1. DougS Silver badge

        Re: With a moon that large

        Well colonists can live on the sea floor, or up in the mountains above the 300 ft tidal surge :)

  7. teebie

    "That would make the ratio between both bodies similar to Earth and the Moon."

    Which is an unusually large ratio compared to what we see in our solar system. Most moons are much smaller in proportion to their planet (argue amongst yourselves over whether pluto is a planet, charon is a dwarf planet and the pair of them are a binary system.)

    1. Flocke Kroes Silver badge

      More big moons in the solar system

      The solar system has four rocky planets, one with a large moon. The moons of the four giant planets are small compared to their primaries but Ganymede, Titan, Callisto and Io are all bigger than Luna also Europa and Triton are bigger than Pluto. There are currently five dwarf planets: Pluto and Eris both have relatively large moons. So far three Trans Neptunian Objects also have large moons (Orcus, Salacia and 2007 OR10)

      (The JWs try to tell me Earth is really unusual because of its large moon. I like to show them this pretty picture)

  8. Hans Neeson-Bumpsadese Silver badge


    the chances of life are pretty slim since the planet is gaseous and not rocky

    Does that really have to be a barrier to life forming? There are plenty of fluid-dwelling creatures in our oceans who I imagine aren't bothered at all that there's a rocky surfaces on Earth. Not such a huge jump of the imagination to consider that life could evolve to float around in a gaseous environment rather than a wetter fluid environment.

    1. Wellyboot Silver badge

      Re: Habitability

      Arthur C. Clarke had precisely that kind of life in his 2010 book.

      Cloud grazers & predators.

    2. Toilet Duk

      Re: Habitability

      True. Scientists hold a religious belief (unsupported by evidence) that life began in primordial seas, the composition of which they do not know and which they are unable to reproduce through experimentation.

      1. pɹɐʍoɔ snoɯʎuouɐ

        Re: Habitability

        the majority of scientists are in no way religious, and scientists will not accept anything as fact without evidence. so to say "Scientists hold a religious belief (unsupported by evidence) that life began in primordial seas" is just not true.

        an experiment back in the 1950's by Stanley Miller and Harold Urey where they mixed a chemical solution of methane, ammonia, hydrogen and water in a flask, which is what the earths early atmosphere and seas were theorised was made up from. They subjected it to an electrical charge and the results was they produced organic compounds including amino acids in the flask. As amino acids are the building blocks of DNA it suggests that this is how life began.

        this is enough for most scientists to accept that that this is how life most probably started and with no theories that have been demonstrated to indicate otherwise it is reasonable.

        If any evidence to the contrary is ever presented then, be sure that because of how science works, scientists will adjust what they accept to be true.

        keyboard, because in most cases if you hit a keyboard with a lightning bolt you could produce a new string of biogenesis .

        1. Primus Secundus Tertius Silver badge

          Re: Habitability

          The Miller experiment showed that a mixture of amino acids and other small organic molecules is readily formed. Since then these compounds have been observed in meteorites and interstellar dust.

          The unanswered question is how do you get from such a mixture to DNA and proteins. Perhaps via RNA, but it is still a question of how do you get to RNA. The analogy is with how do you turn a pile of bricks, doors and windows into a house? Pushing the analogy further, did things start with a tent that then somehow turned into a house?

          It has been suggested that clay played a part; or that a primitive "soup", very dilute, somehow reacted with hot rocks reached through cracks in the ocean floor. Neither of these options would be available on a gas giant planet.

  9. imanidiot Silver badge

    Orbital stability

    Just how stable would be the orbit of the moons moons? (Moonlets?, Metamoons?). If the parent body is that large the point where an orbit around the moon is stable would be quite close to the moon I'd imagine, making it possible the moon wouldn't have any stable moons and swap them with the host planet from time to time

    1. Wellyboot Silver badge

      Re: Orbital stability

      Minor moons (moon-1? ) swapping orbits between bigger moons & host planet?

      I don't know how Newtonian physics can produce a repeating double slingshot for this, it would seem to require a really tight set of numbers for planetary mass, major moon orbital distance & mass, minor moon orbital velocity and all orbital planes being aligned precisely.

      If it can be simulated then it will be happening somewhere out there. (Pity the poor Galileo living there trying to figure out WTF is happening in the sky)

      1. LDS Silver badge

        Pity the poor Galileo living there

        IIRC there's a sci-fi (Asimov?) short story about a civilization living on a planet orbiting many stars - so they could discover a gravitation theory only very late in their civilization because of the complexity of it in their environment - just they never have a real, dark night but every n centuries or millennia - so when it happens they get mad and the civilization crumbles, so they have to start anew...

        Throw in some large moons with moons, and it can soon get very, very complex... still Galileo didn't went into the required math, it was Kepler who was able, by analyzing Tycho carefully recorded data (without a telescope) - especially of Mars, IIIRC -, to understand they could fit an elegant mathematical model.

        1. onefang Silver badge

          Re: Pity the poor Galileo living there

          "IIRC there's a sci-fi (Asimov?) short story"

          Yes it was Asimov, called "Nightfall". He later expanded it to a whole book.

  10. Anonymous Coward
    Anonymous Coward

    isn't it probably the case that all bodies in space have their own moons? and they in turn have their own moons?

    isn't that just how gravity works for objects that're close enough to a larger object but not so close they get sucked into them?

    maybe i'm misunderestimaficating how spaaaaaace works.

  11. Stevie Silver badge


    Well, "yea science!" and all that but of what value is this other than in refining technology? I mean, any life "discovered" will be 8000 years ago, no?

    If you want to see planets* circled by other bodies, each with their own moon system, one need only watch "Firefly" or check out any number of paintings by the great artists of SF.

    * Arguably. Since we cannot resolve the orbital crap over such distances, we cannot claim that any "exoplanet" has cleared its own orbit and - according to the wisdom of the De Grasse Tyson Claque - cannot therefor classify them as planets at all.

  12. NanoMeter


    Moons orbiting moons should be called "Moon-moons".

    1. Anonymous Coward
      Anonymous Coward

      Re: Moon-moons

      I want to call them Moonmins, after the Moomins cartoon from my childhood.

    2. onefang Silver badge

      Re: Moon-moons

      It's moons all the way down.

    3. Anonymous Coward
      Anonymous Coward

      Re: Moon-moons

      > Moons orbiting moons should be called "Moon-moons".

      Definitely. See

  13. richardcox13

    More work to do

    The boffins need to get on with this, after all they only need to find a billion billion exomoons to have an exaexomoon.

  14. Conundrum1885

    Not allowed to call this one

    Moony McMoonface.

    (gets coat)

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