A new planet in our solar system?

Given that we now have telescopes that can probe far into the most distant regions of the universe, and are even able to detect the existence of what are known as exoplanets (i.e., planets orbiting stars other than our own Sun), you would think that we would pretty much know everything that exists in our own neighborhood of the solar system.

Hence there has been considerable excitement about the possibility of a new planet in our system. This postulated planet is not a small object like Pluto but has a mass that is ten times that of the Earth. What makes some scientists suspect that it is there? The reasoning is similar to the way in which astronomers Adams and Leverrier predicted the existence of Neptune back in 1846, by observing the anomalous behavior of other celestial objects such of Uranus.

Two researchers from the California Institute of Technology have discovered evidence for a massive planet orbiting the sun far beyond Neptune. Using mathematical and computer models, Michael Brown and Konstantin Batygin looked at objects behaving strangely in the Kuiper belt, a region beyond the eight planets filled with minor planets similar to Pluto, asteroids and other rocky bodies of varying sizes.

They concluded that another planet, which they call “Planet Nine,” must be responsible for these peculiarities. They reported their findings Wednesday in The Astronomical Journal, an open-source publication.

Brown and Batygin built upon the findings of a 2014 paper by a separate team of astronomers. That team discovered an object roaming beyond Neptune with an unusually elliptical orbit, similar to that of the previously discovered minor planet Sedna. They nicknamed their discovery “Biden,” after the vice president, and put forth the idea that the gravitational pull of a large planet could be responsible for the object’s orbit.

Further research by Brown and Batygin showed that at least six objects, including Biden and Sedna, as well as other, smaller bodies, followed similarly aligned oval-shaped orbits. This behavior could not be explained by current models of the solar system and offered strong evidence that an unknown force was at work.

In their current study, Brown and Batygin used computer simulations to work through the various possibilities to explain the peculiar orbits. They considered, and then discarded, scenarios where the gravitational pull of the Kuiper belt itself was responsible for the odd orbits. Also rejected was the theory that a large planet could be encircling all of the objects and influencing them from the outside. They inserted planets of different sizes into their projections, and found that the only way to describe the six Kuiper belt objects’ behavior was a body substantially larger than Earth on a long orbit around the sun passing through the Kuiper belt.

So if it does exist, how could we have missed it for so long? This planet, although much bigger than the Earth, has a very large orbit, at its farthest point being about 1,200 times the distance from the Sun as the Earth is, and its orbit takes about 10,000 to 20,000 Earth years.

This is not the first time that new planets have been suggested but those earlier speculations did not pan out and until there is more direct proof of its existence, this will not enter science textbooks.

Still, it is nice to think that the possibility exists of astronomical treasures still undiscovered in our own backyard.


  1. Chris J says

    Just goes to show how all our pictures of our solar system are literally just artist’s impressions, not actual photographs from deep space. We know some much about our universe, but not because we’ve gone out and traveled around in a space ship; it’s all been about models and tiny telescopes.

  2. Robert,+not+Bob says

    If there is another major planet, I’m voting for “Persephone”. But I’d prefer to wait for telescopic evidence. Have they detected Nemesis yet?

  3. StevoR says

    @2. Robert,+not+Bob : Nemesis – at least in terms of a companion star or even brown dwarf orbiting our Sun has been pretty much ruled out based on the WISE (Wide Field Infrared Survey Explorer) space telescope. WISE :

    .. was able to detect any objects warmer than 70–100 K. A Neptune-sized object would be detectable out to 700 AU, a Jupiter-mass object out to 1 light year (63,000 AU), where it would still be within the Sun’s zone of gravitational control. A larger object of 2–3 Jupiter masses would be visible at a distance of up to 7–10 light years …


    March 7, 2014 — NASA reports that WISE, after an exhaustive survey, has not been able to uncover any evidence of “Planet X”, a hypothesized planet within the Solar System.[40]

    Source : https://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer#Targets_within_the_Solar_System

    For the record Neptune weighs in at 17 Earth masses and Ouranos at 14.

    There’s also this Q & A :

    . Nemesis would have followed a highly elliptical orbit, perturbing comets in the Oort Cloud roughly every 26 million years and sending a shower of comets toward the inner solar system. Some of these comets would have slammed into Earth, causing catastrophic results to life. Recent scientific analysis no longer supports the idea that extinctions on Earth happen at regular, repeating intervals. Thus, the Nemesis hypothesis is no longer needed. However, it is still possible that the sun could have a distant, unseen companion in a more circular orbit with a period of a few million years — one that would not cause devastating effects to terrestrial life.

    from the WISE website here :


    Scroll down to end – but reckon the whole thing is interesting and worth reading.

    It certainly isn’t the first time that studies have suggested the presence of a larger trans -Neptunean planet based on orbital dynamics – most of which have come to very little. I’ll believe it when we actually see it. Fascinating and suggestive finding / modelling here – but certainly not conclusive and a but premature to say much more than that.

  4. Robert,+not+Bob says

    I hadn’t looked at the information in depth, but I never thought much of the Nemesis hypothesis, and I’m not surprised. Seems to me probability is enough to explain the supposed periodicity of mass extinctions.

    Was I wrong to assume the Kuiper Belt objects pretty much nixed the possibility of further gas giants? Space is big…

  5. StevoR says

    @ ^ Robert,+not+Bob : Kinda, wrong yeah. The kuiper belt objects don’t necessarily rule out another gas giant -and as this study suggests they may (or may not)lead to finding it using their orbits as a type of guide. There’s been a lot of speculation about possible gas giants in the outer solar system and one plausible model which fits the calculations and observations ha sit that a fifth gas giant should have formed as well as the four we know – then been ejected from the solar system – but perhaps it could’ve been merely cast into the depths of the very distant solar system – even the Oort cloud – instead.

    The thing that does seem to rule out at least a planet up to X mass in Y orbit is the fact that if it was there we should’ve picked it up on one of the many searches made for it so far. Including not just Tombaugh’s but the WISE survey and many astronomical searches that have found of lot of smaller objects including the other ice dwarfs like Eris, Sedna, Haumea etc … A lot of these have been pretty extensive and used a lot of increasingly advanced technology so .. If something is out there we know it’ll have to be less than X mass for Y orbit or alternatively beyond Y orbit for X mass. (insert values of ‘X’and ý'” for each relevant search eg. the WISE survey ones listed above.) Basically a lot of possibilities for how big and close any hypothethised extra gas giant(s) could be have already been pretty definitely eliminated.

  6. Rob Grigjanis says

    Robert @2:

    If there is another major planet, I’m voting for “Persephone”.

    Convention favours Roman names, so that should be “Proserpina”.

  7. Wotan Nichols says

    If such a body is actually found, they may have to tweak the new definition, the controversial one which demoted Pluto. It seems doubtful that any new planet, even if it be 5 or 10 X Earth’s mass, could ‘clear out’ such a large orbit in the way that the known planets have done.

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