Earth-Sized Planet in the Kuiper Belt

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Japanese researchers have used computer simulation and the orbits of several large objects past Neptune to calculate that there is Kuiper Belt planet (KBP) 1.5–3 times as massive as Earth, located at ten to twenty times further than Neptune (250–500 au). A trans-Neptunian object (TNO) is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units.

The researchers found several objects with unusual orbits and calculated that the unusual orbits had to be caused by an object 1.5 to three times bigger than the earth out ten to twenty times farther from the Sun than Neptune.

The results of the KBP scenario support the existence of a yet-undiscovered planet in the far outer solar system. Furthermore, this scenario also predicts the existence of new TNO populations located beyond 150 au generated by the KBP’s perturbations that can serve as observationally testable signatures of the existence of this planet. More detailed knowledge of the orbital structure in the distant Kuiper Belt can reveal or rule out the existence of any hypothetical planet in the outer solar system. The existence of a KBP may also offer new constraints on planet formation and dynamical evolution in the trans-Jovian region.

The orbits of trans-Neptunian objects (TNOs) can indicate the existence of an undiscovered planet in the outer solar system. Here we used N-body computer simulations to investigate the effects of a hypothetical Kuiper Belt planet (KBP) on the orbital structure of TNOs in the distant Kuiper Belt beyond ∼50 au. We used observations to constrain model results, including the well-characterized Outer Solar System Origins Survey (OSSOS). We determined that an Earth-like planet (m ∼ 1.5–3 M⊕) located on a distant (semimajor axis a ∼ 250–500 au, perihelion q ∼ 200 au) and inclined (i ∼ 30°) orbit can explain three fundamental properties of the distant Kuiper Belt: a prominent population of TNOs with orbits beyond Neptune’s gravitational influence (i.e., detached objects with q > 40 au), a significant population of high-i objects (i > 45°), and the existence of some extreme objects with peculiar orbits (e.g., Sedna). Furthermore, the proposed KBP is compatible with the existence of identified gigayear-stable TNOs in the 2:1, 5:2, 3:1, 4:1, 5:1, and 6:1 Neptunian mean motion resonances. These stable populations are often neglected in other studies. We predict the existence of an Earth-like planet and several TNOs on peculiar orbits in the outer solar system, which can serve as observationally testable signatures of the putative planet’s perturbations.

Is There an Earth-like Planet in the Distant Kuiper Belt?, The Astronomical Journal

20 thoughts on “Earth-Sized Planet in the Kuiper Belt”

  1. Just a thought. But at that distance from the sun the suns gravity influence is much reduced.

    I wonder what the chances are that the object is a planetary binary?

    Even the earth at 1 AU has a large satellite.

    And Pluto and Charon are even more similar in size to each other.

    If a close binary could it potentially also have internal heating and I wonder how much?

  2. If the atmosphere is thick enough, temperatures at the surface could allow liquid water, from geothermal heating. This was mentioned in “Worlds Without End” by Chris Impey, read years ago.

    • Hi William
      David Stevenson first posited geothermally warmed quasi-interstellar worlds with deep hydrogen atmospheres. This was further studied in the 25 years since.

    • “the place this planet is expected to be” is an orbit 500+ AU in diameter. There is absolutely no guarantee for this planet to be anywhere near where New Horizons might look, even if it is in that same orbit.

        • Above the ecliptic has a major disadvantage over our current position, roughly the middle of the Solar system, because you would only see around half the light reflected from the Sun off the planet.

          • True, but you get an overview of the entire orbital plane, with a smaller portion of the sky in the background.

  4. … and new opportunities for exotic life forms.

    What if Brown Dwarfs turn out to be scattered by the dozens or hundreds in the space between the stars? And what if most of them have mini-solar systems (like Jupiter and Saturn) capable of supporting life because there is enough heat is generated by the BD to allow liquid water and photosynthesis based on infrared frequencies? It’s easy to imagine life based on infrared photosynthesis on moons orbiting brown dwarfs which give off heat but not light. Not just imagine it, we already know of such life here on Earth: green sulfur bacteria. And if BDs floating between the stars greatly outnumber suns, then visible light spectrum based life may be the exception instead of the rule.

    In addition to infrared based life, Cornell researchers have modeled methane based life forms that don’t use water and could live in the liquid methane seas of Titan. Methane based life forms by themselves are a fascinating concept. But ironically the potential “Goldilocks” zone for such life is far greater (extending across the range of Jovian worlds out to the Kuiper belt) than our narrow zone for water based life forms.

    So “life as we know it” based on water and the visible light spectrum photosynthesis may be the rare exception in a universe dominated by methane based life and life that utilizes infrared photosynthesis.

  5. This suggests and intermediate step between colonizing the solar system and colonizing the stars – exploration and colonizing of the planets between the stars.

    http://www.scifi.com/sfw/issue183/labnotes.html

    “What if space is littered with these failed stars, scattered between the bright ones like a stellar Polynesia, making interstellar travel a series of short hops, rather than a single gigantic one? What if a simple fusion reactor carried just enough fuel to push a spacecraft to our solar system’s Planet X in reasonable time? What if it could refuel there, harvesting just enough hydrogen or deuterium or helium to limp along to another dark neighbor, and another, and another? Granted, it would take a long, long time to get to Alpha Centauri that way, and probably a much, much longer time to find a planet somewhere that looked even remotely like our rain- and sun-drenched Earth. But given the likelihood of tidally warmed moons, and the obvious possibilities for life there, we may just find that the cold, dark spaces are where most of the action is anyway.”

    There may be dozens or hundreds of mini-solar systems between Sol and Alpha Centauri. With the discovery of BDs, free floating planets between the stars, and extra-solar planetoids like Sedna, future space explorers may find plenty to keep them occupied in our own solar neighborhood for centuries to come. While not the galaxy spanning empires and federations of science fiction, it would be enough for our species to explore far into the future.

    And since these mini-solar systems and planets are a stone’s throw away, they can be reached without exotic warp drives or hyperspace jumps. Simple solar sails, laser sails or nuclear rockets will do just fine. Exploration missions can visit and return in a matter of years, instead of centuries or millennium. Interstellar “empires” and “federations” can be created using slower than light space travel.

    Maybe Capt. Kirk and Obi Wan Kenobi wouldn’t be impressed, but we’ll be half way to Alpha Centauri.

    • The Oort cloud of icy of bodies may extend more than half the distance to Alpha Centauri, by some estimates. If that is so, and assuming Alpha Centauri has a similar Oort cloud, then there’s a continuous zone of icy bodies all the way there. No need for a 10th planet or brown dwarfs etc. The problem is that the icy bodies are still fairly far apart, and difficult to detect. So it’s not easy to tell where to go next.

  6. Hi Brian
    A residual primary atmosphere of H/He could mean the KBP has liquid water oceans even at 250-500 AU. Of course the surface pressure will be high, but it’s an intriguing prospect.

  7. Earth sized. If it were Earth-like I’d think we’d have seen it cuz ice balls are bright. Isn’t there math that could tell us how visible it’d be given an albedo and a light source?

  8. Call it an Earth-sized planet. It is not an Earth-like planet.

    The paper postulates a second Kuiper belt as well.

    • Depends how it got there and where it came from. If it’s Earth-like in composition, it could have a global sub-surface ocean. The surface may look different by direct comparison, but that’s not what Earth-like means in a planetary science sense.

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