Is it possible there are planets with extremely long orbits that pass through our solar system?

Question

I'm refering to the planet X theory but just how possible is it there are large planets with orbits like comets that pass through our solar system occasionally.

Astronomy has recently discovered some that go around Neptune and Uranus but it would be interesting if one actually passed by all the planets orbiting around the sun itself before going back out into space.

Answer 1

There is a lot of confusion about the words "Planet X". As originally coined by Percival Lowell in the early years of the 20th Century, this was X as an unknown entity as in algebra and NOT the Roman numeral for ten and it was a hypothetical planet that was postulated as existing to explain certain discrepancies between the predicted and observed orbit of Neptune.

When the Voyager I and II flybys took place it was possible to recalculate the mass of Neptune and Uranus and when these figures were used in preference, the discrepancies disappeared. The Planet X theory was abandoned as a result,

BUT

in the last few years when Eris was discovered, the phrase Planet X as the 10th Planet and X for Xena was bandied around as the issue of Xena being bigger than Pluto could not be ignored and pressure to include Xena in the list of planets was put on the IAU by NASA, among others.

These were both genuine scientific quests and debates. But the position got muddied and confused further by the Nibiru mystics and Wormwood Christians for whom science had no interest and relevance who also had hypothetical planets which they were convinced would return. But they felt no obligation to say where these were and what their orbits were, i.e. work by the well-established ground rules for recognising, cataloguing and naming new celestial objects in the Solar System.

The idea that large planets wander in casually on the spur of the moment into the inner Solar System from outside the heliopause and then drift out again to whence they came is basically an intellectual cop-out arising from being unable to state their pet planet's orbit and position within it when challenged.

It seems being a celestial object positively dripping with claimed portentous significance somehow exempts Nibiru and Wormwood from obeying The Laws of Physics and somehow protects them from anything so mundane as being seen in a telescope and photographed before they arrive!

So the notion they lurk furtively and skulk malevolently somewhere inbetween stellar systems has an appeal as it avoids having to be too specific.

But the same questions are still posed: what makes these hypothetical planets enter the Solar System? What makes them leave it again? Is there a periodic pattern to their visits (as with comets)? Those questions don't go away by saying they mostly live outside the Solar System rather than they mainly live way beyond Pluto.

The short answer as to whether planets could have long orbits is yes. Pluto is 248 years, Eris 550 years, Sedna 12,050 years.

The short answer as to whether they could penetrate hrough to the inner solar system, past the gravitational pull os the four gas giants has to be "very doubtful".

(a) Despite Sedna's huge semi-major axis of over 500 AUs as it comes in from an aphelion of 975 AUs (in the Oort Cloud) its perihelion remains beyond Pluto's orbit and it does not get anywhere near the gas giants, despite its long journey.

(b) The 1994 impact of the comet Shoemaker-Levy 9 crashing into Jupiter shows the kind of fate that awaits celestial objects that come too close to Jupiter's enormous gravitational influence.

Answer 2

It's possible ... just not at all likely. The orbits of the planets, including Pluto and the major asteroids, are pretty well known. They can be backwards predicted for 1000's of years, and don't show any significant perturbation by some unknown planet X. Anything the size of Pluto that passed through the solar system would have almost certainly disturbed the orbits enough for us to still see the results.

There could be a large planet X out there, beyond the orbit of Neptune. But it's not reasonable to expect that it passed through the inner solar system anytime in the previous 100,000 years.

Answer 3

Should this be true the planet would most likely be pulled into the sun itself during its orbit through the solar system. A planet circling another star that cannot hold it in orbit has a very high G force. It could even attract other solar system planets in a moon like relationship around it. No, I don't know anything about planet X, but it does not seem logical to me. An asteroid belt can do it, but not something really heavy (with the exception of my late husband's ex wife).

Answer 4

mmm I don't see why not. If you look at the solar system now, its very 2d, its almost a flat line. Like nothing is above or below Earth, that doesn't seem right to me. Pluto has shown that (Dwarf) Planets don't have to follow just that stright line. I don't see why other planets couldn't be orbiting the sun in away we just haven't looked for it yet, not saying that like a planet could be between Earth and Mars, but like Pluto and Neptune they share an orbit and never touch, Space is huge, so its not impossable a planet even near by could stay hidden if we're not looking right.

I have no sources, this is just from my understanding of astronomy.

Answer 5

The farther away a planet is the larger the orbit. There is probably a limit on how long the orbit can be because if the planet ventures too far away from our solar system the gravity of the sun wont be able to bring it back to keep it in orbit.

Answer 6

Possible but no easy.
As the planets have been formed near and around a star and it is not easy to acquire the escape speed to leave their orbit around the star, the only way to have a 'free interstellar planet' is with the help of a strong gravitational pulling. If two galaxies collide, many stars from one of the galaxies would pass near the stars from the other galaxy. So after those collisions surely many planets would be traveling with hyperbolic orbits in the interstellar and intergalactic space.

Answer 7

It is possible I suppose. Comets are in such orbits, and I suppose some really big comet could be out there. But so far none has been seen. But we are talking about orbits that would have to be hundreds of times bigger than the orbit of Neptune.

Answer 8

If there were, they wouldn't be called planets, they'd be called comets, or something like that. And they wouldn't be very big.

Second poster (Terry D) - please don't say "it's just a theory" when what you really mean is, "it's just a guess." A theory is an idea that has tons of supporting evidence from many different fields, and has stood the test of time - withstanding many attempts to prove it wrong.

Answer 9

It is a possibility, but I am not enough of an astronomer to know how to go about proving such a thing. Pluto was, of course, discovered following a search for a Planet X.

Answer 10

I don't think its very likely. It seems to me that large bodies would be trapped in a mostly circular orbit around the Sun. But I don't think its likely, but its possible.