Scientists Find Hints Of A Giant, Hidden Planet In Our Solar System

Jan 22, 2016

Photo credit: Caltech/R. Hurt (IPAC)

By Nell Greenfieldboyce

The astronomer whose work helped kick Pluto out of the pantheon of planets says he has good reason to believe there’s an undiscovered planet bigger than Earth lurking in the distant reaches of our solar system.

That’s quite a claim, because Mike Brown of Caltech is no stranger to this part of our cosmic neighborhood. After all, he discovered Eris, an icy world more massive than Pluto that proved our old friend wasn’t special enough to be considered a full-fledged planet. He also introduced the world to Sedna, a first-of-its-kind dwarf planet that’s so far out there, its region of space was long thought to be an empty no man’s land.

Now Brown has teamed up with Caltech colleague Konstantin Batygin to do a new analysis of oddities in the orbits of small, icy bodies out beyond Neptune. In their report published Wednesday in The Astronomical Journal, the researchers say it looks like the orbits are all being affected by the presence of an unseen planet that’s about 10 times more massive than Earth — the size astronomers refer to as a super-Earth.

“I’m willing to take bets on anyone who’s not a believer,” says Brown. He thinks existing telescopes have a shot at spotting this mystery planet in just a few years, since this new study points to a band of sky where astronomers should look.


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10 comments on “Scientists Find Hints Of A Giant, Hidden Planet In Our Solar System

  • They can’t call this one the 9th planet no matter how big it is unless it’s found orbiting in the ecliptic plane. They will have to give planet 9th planet status back to Pluto and maybe planet status to some others. This big fucker may be sent to the back of the planet naming line…



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  • DWH
    Jan 22, 2016 at 12:57 pm

    They can’t call this one the 9th planet no matter how big it is unless it’s found orbiting in the ecliptic plane.

    That’s not how the naming system works. If a planet is found to be causing these gravitational effects, it will be classified by size, not orbit.

    They will have to give planet 9th planet status back to Pluto and maybe planet status to some others.

    Pluto and any other spheroid planetoids which are not moons, will be classed as “dwarf planets”.



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  • If there is a planet this far out it could be a binary or have a bunch of moons.

    As Pluto has shown, the Sun’s gravity is so weak this far out, that even dwarf planets which would have no chance of retaining moons in the inner Solar-System, can retain substantial moons or groups of moons.



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  • Pluto wasn’t demoted due to its size nor its orbital path. The main reason is because it has not cleared its neighbourhood.

    If this object is found and is 10x earth size, it will almost certainly have cleared its neighbourhood, allowing it to pass that requirement, and thus giving it a very good chance to be classified as a planet.

    Smaller objects, like Pluto, aren’t large enough to clear their neighbourhoods.



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  • Adam Leathorn
    Jan 23, 2016 at 11:34 pm

    Pluto wasn’t demoted due to its size nor its orbital path. The main reason is because it has not cleared its neighbourhood.

    This is a problem for any planet which is in an eccentric orbit, as its orbit is likely to cross the orbits of other planets, with the band to be swept enormous and rarely visited, for any planet without a near circular orbit.

    https://en.wikipedia.org/wiki/Planets_beyond_Neptune#/media/File:Planet_Nine_Orbit_%28without_background%29.svg



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  • Adam Leathorn
    Jan 23, 2016 at 11:44 pm

    Planet definition time, and its relation to Pluto demotion:

    As I mentioned in my previous comment, if there is a large planet beyond Neptune in a eccentric orbit, this orbit is likely to cover a very extensive area of space with an exceedingly long orbital year. Such a planet would be unlikely to have “cleared its orbit” as clearing an orbit is a bit nominal in the size of objects cleared (Earth is still bombarded with thousands of tonnes of space dust and meteorites each year), and a nominally cleared orbit, is a feature of circularised orbits.

    @ Universe Today link – Pluto was still a planet, and so were Eris and even Ceres, which had been thought of as the largest asteroid. A different proposal kept the total at 9, defining the planets as just the familiar ones we know without any scientific rationale, and a third would drop the number of planets down to 8, and Pluto would be out of the planet club. But, then… what is Pluto?

    The essential features of a planet are the spheriod form resulting from gravitational collapse of the structure, and the property of orbiting the Sun directly, rather than being a moon of a larger planet which orbits the Sun.

    In the end, astronomers voted for the controversial decision of demoting Pluto (and Eris) down to the newly created classification of “dwarf planet”.

    We have classifications of planet types already – Rocky planets, gas-giants, and ice giants, so adding dwarf planets as a new category for spheriod asteroids and Kuiper-Belt objects, makes sense.

    Failing to recognise the new class, because of tradition makes no sense.

    There is a possible future classification problem with extra-Solar-System discoveries, in that it is possible that small rocky planets may be found close to their stars. These would not closely resemble the icy dwarf planets of the outer solar-System.



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  • @Alan4discussion

    Yes, a new classification of dwarf planet was introduced. However, I think you are incorrect in assuming that a large planet wouldn’t have “cleared its neighbourhood” if it were beyond the orbit of Neptune. We’ll have to look at the definition of “clearing the neighbourhood” as defined by the IAU, instead of relying on your personal opinion on the subject. I’m happy to see you have a higher level of understanding for a lot of these topics, but I think you are applying personal opinion about what constitutes “clearing” by saying it’s a “bit nominal in the size of objects cleared.” Again, this is something that has been defined and agreed upon by the IAU, so we can look at their definition. Specifically this part:

    “meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence”

    Therefore, a large planet out beyond Neptune would likely be the largest object out there and it would likely be gravitationally dominant, so it would thus be considered a planet. An object about the size of Earth out in Plutos orbit would be a bit of a debate as to weather or not we should be calling it a planet, I think. I think it would still pass all three “planet” tests, though–especially a “super-Earth.” I can only guess as to how big that would be, but a planet twice the size of Earth would be about 11 times the size of Pluto, and would be the dominant object in its orbit if it were in the same vicinity as Pluto.

    The example you gave with the Earth can be thrown out, as the debris you’re referring to is not anywhere near as large as Earth, and Earth is obviously the gravitationally dominant body it its orbit–by a long shot.

    Read here: https://en.wikipedia.org/wiki/Clearing_the_neighbourhood

    I would have to agree with Neil deGrasse Tyson when he talks about the rocky planets as being classified as the dwarf planets. I mean, our four inner planets are dwarfs compared to the gas giants, really.

    Also, exoplanets don’t actually fit into these classifications. I’m sure they will have influence on future naming conventions, but currently the term “planet”, as defined by the IAU, only applies to objects orbiting our sun, not objects orbiting other stars.



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  • Adam Leathorn
    Feb 15, 2016 at 1:45 pm

    I’m happy to see you have a higher level of understanding for a lot of these topics, but I think you are applying personal opinion about what constitutes “clearing” by saying it’s a “bit nominal in the size of objects cleared.” Again, this is something that has been defined and agreed upon by the IAU, so we can look at their definition.

    The points you make are valid for the inner solar-System, where orbits are roughly circular, and planets are sufficiently close together to interact fairly strongly.

    Specifically this part:

    “meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence”

    The issue in the far outer Solar system, is that orbits are so long, spaces between bodies potentially vast and gravitational interactions weak, so that especially with eccentric orbits, close interactions are likely to be rare.

    This point which I made is quoted on your Wiki link.

    The phrase refers to an orbiting body (a planet or protoplanet) “sweeping out” its orbital region over time, by gravitationally interacting with smaller bodies nearby. Over many orbital cycles, a large body will tend to cause small bodies either to accrete with it, or to be disturbed to another orbit, or to be captured either as a satellite or into a resonant orbit. As a consequence it does not then share its orbital region with other bodies of significant size, except for its own satellites, or other bodies governed by its own gravitational influence. This latter restriction excludes objects whose orbits may cross but that will never collide with each other due to orbital resonance, such as Jupiter and its trojans, Earth and 3753 Cruithne, or Neptune and the plutinos.[3]

    In the Oort cloud and the Kuiper belt, there are many eccentric planet crossing orbits which are unlikely to collide because of the vast distances and times involved, in addition to many minor bodies perturbing each other.

    As to the extent of orbit clearing required, Jean-Luc Margot emphasises “a planet can never completely clear its orbital zone, because gravitational and radiative forces continually perturb the orbits of asteroids and comets into planet-crossing orbits”

    Which is the point I made about thousands of tonnes of meteorites and dust falling on to Earth.

    and states that the IAU did not intend the impossible standard of impeccable orbit clearing.

    Which is what I meant when I said “it was a bit nominal”!

    http://www.space.com/16144-kuiper-belt-objects.html

    Sedna (sed’nah), about three-fourths the size of Pluto, was discovered in 2004. It is so far out from the sun it takes about 10,500 years to make a single orbit. Sedna is about 1,100 miles (1,770 km) wide and circles the sun on an eccentric orbit that ranges between 8 billion miles (12.9 billion km) and 84 billion miles (135 billion km).

    With these time scales an distances, repetitive close encounters are very unlikely for Kuiper Belt Objects.
    Oort Cloud objects are even further out with vastly longer orbits, and are not even roughly in the plane of the ecliptic!



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  • Adam Leathorn
    Feb 15, 2016 at 1:45 pm

    Therefore, a large planet out beyond Neptune would likely be the largest object out there and it would likely be gravitationally dominant, so it would thus be considered a planet.

    This is where the classification system which works approximately in the inner Solar System on roughly circular orbits breaks down.

    The celestial mechanics of a planet in a very long eccentric eccentric orbit in the outer Solar-System, would have Apsidal Precession which would make the area covered by it in its orbit, vast: (see link animation) – with most areas in that “nominally swept” area visited extremely in frequently – even on astronomical time-scales. The great distances would mean that its gravity would be extremely weak over most of the “swept” area most of the time.



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