Could an 'Earth-like' planet be hiding in our solar system's outer reaches?

Sep 20, 2023
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If there was a planet where this article I suggesting scientists think there might be, it would be NOTHING close to an Eath like planet. For another Earth like planet to exist in our solar system, It would have to be within the the distance of Venus to Mars , what scientists call the "Goldilocks zone" . The Author just used a clickbait headline to write another piece about planet X/ Nibiru. Nothing new. Now a theory that is interesting and would fit the click bait title is the possibility of a planet directly on the other side of the sun with the same speed as us around the sun, to were the only way we would know is getting to Venus or Mars to triangulate a view via ships Satellites or planetary stations with radar.
I think they mean Earth-size planet.

In 1969, the movie “Journey to the Far Side of the Sun” also known as “Doppelgänger”, was exactly about another Earth in the same orbit but opposite our Earth. The culture was an exact mirror image of us.
Wouldn't we by now be able to see the effects of Earth's "twin" on other planets' orbits, if it was really there? Not to mention our interplanetary satellites that would have passed it and had their trajectories "mysteriously" altered.
Not only that, but any two planets in the same orbit opposite one another would be in one another’s L3 point, they will eventually drift away from those points and will eventually be visible. In the long term they pass one another or collide, hence the Theia theory.
Pogo, I'm not so sure that the L3 point would be unstable if there were 2 identical mass planets on the opposite sides of the Sun. The L3 calculation assumes a much smaller mass than the 2 bodies that define it. If the masses were the same size, their orbits would be the same radius with the same period. And, since the Sun is the dominant player in the attraction, the effects of the two planets on each other seems small, at least compared to the effects of other planets passing by both at different times. So, I do agree that the concept of another planet in an identical orbit around the Sun should get perturbed out of that position in 4.6 billion years, but mainly because the effects of the other planets would tend to have non-identical perturbations on the different planets at somewhat different times.
This report seems to do much to support Brown's original work placing Planet IX to about 600 AU based on the orbital anomalies he was able to measure. These refined measurements bring this estimate to less than 500 AU. They also estimate the mass to be less, but this is logical since their version is closer to the TNOs they've measured -- inverse sq. law.

Although, the planet, if found, is far outside the HZ, lets not exclude entirely it could have a warm-enough moon to host liquid water. We see this for many moons in our system, due heavily to tidal stress. Water is ubiquitous, but certain conditions, of course, are needed for it to be in a long-term liquid phase. Pessimism is warranted for any life prospect out there.
Wouldn't we by now be able to see the effects of Earth's "twin" on other planets' orbits, if it was really there? Not to mention our interplanetary satellites that would have passed it and had their trajectories "mysteriously" altered.
Well, one would think so. But, this seems to be a story we've seen before. Leverrier , a young buck at the Paris Obs., calculated where a planet must be to explain the orbital anomaly of Uranus. It's possible they didn't like his arrogance, IMO, so he finally handed to one of the few who would bother with his prediction. The German astronomer he gave it to discovered it that very night he first looked. [But unlike Herschel, he did not propose the name of George, darn it!]

But 40AU is a lot easier than 400 AU, or more.

With the great ability of IR imaging, which reveals the most distant objects in our system much better than visual, it's been a surprise, to your point, that nothing has surfaced. Some think the background glow of the MW is inhibiting the discovery.

A counter-model was presented shortly after Brown presented his model. I can't recall her name (Irish) , but she demonstrated that the TNO's themselves may have enough mass collectively to cause the odd orbital anomalies. I don't think this was ever debunked.
L4 and L5 are stable especially for a larger planetary body, hence Jupiter’s Trojan family. L1, L2, and L3 are inherently unstable, see the Wikipedia article ‘Lagrange points’, especially that the Earth is pretty small and it’s orbit has a small eccentricity. If there was a body at L3, when the Earth or anti-Earth is at perapsis and the other is at apoapsis, the orbital velocities are different enough that one should appear enough ahead or behind in its orbit to be visible to the other.
L3 might be more stable if the Earth’s orbit was circular and it was the only planet. But, since all 8 planets tug on the Sun, even to the point that occasionally the barycenter is actually outside the body of the Sun, the L3 point can’t really hold anything.
There is no mirror object at L3 because we have sailed to the "dark side" of the Sun with more than one probe (e.g. Parker), and nada. :)

All the Earth's La Grange points are too close to the Sun to help find a distant planet in our system. Also, at 500 AU, the orbital period is over 11,000 years, so catching perturbations in orbits of, say, Neptune might be a problem. :)

The inability to see large planets just a few thousand AU away, while being able to see these same -sized objects that are a million or more AU away orbiting other stars is one of those cute quirks I find that add to the greatness of astronomy.

Consider that Jupiter is invisible to the HST if it were to move out to only ~ 10,000 AU, 1/6th the distance to the outer solar system. [The JWST, however, can see it farther out because of its larger mirror and its IR capabilities.] But both of these can observe directly a select few orbiting other star systems.

The reason is the inverse fourth power, which is the inverse square law for light propagating out of the Sun. But it is also the inverse square law that must be applied to the light that is reflected off the planet, hence their product (inv. 4th power). Not many photons make it back.
Would Parker be able to see asteroids in L3?
Since it studies the Sun, it's unlikely Parker can see any dim object. But something its size could be sent to do this, and it might be a good idea. [Perhaps this is planned, but it won't be near as cheap as something at L2.]

The weakest link in our asteroid watch system, I assume, is catching dangerous asteroid, or comets, that swing around the back side of the Sun and get tossed our way. The challenge even for space telescopes is to not suffer by viewing near the region around the Sun due to extreme glare. IIRC, the HST is not allowed to swing within 51 degrees of the Sun in order to avoid sensor damage.

So, and L3 asteroid hunter would be great to have, but it needs a sister at L4 or L5 to relay the data, I suppose.
I wonder if it is a different sensation in a L point. There is no fall in a L point, right? A true float? How large or what volume does a L point have? Does one need to stay in it with rotational motion? Angular momentum? Does the mass matter in the L point? Could another moon reside there? Could we dock distant cargo there? Would a large mass in a L point effect Earth's orbit?

Curious things these L points.
Is radar blinded by the Sun, like light?
Stars are crazy EM sources. Radio astronomy hopes to build on the farside of the Moon because it’s very noisy here on Earth, as well.

There are two models the can address Lagrange points — Newtonian and GR (General Relativity).

Lagrange used Newton’s gravity model. About 1 million miles from Earth toward the Sun is L1. This is the point where the pull of gravity from the distant Sun matches the pull from Earth. It’s a balance, but it’s a dynamic model, as well, due to our orbit, which is the only way an L4 & L5 make sense.

GR presents a model where the gradient in space (space time) formed by both Earh and the Sun varies relative to their mass and distance. Lagrange points are like dimples that exist in an elastic fabric. Objects that gently drift in these dimples can get stuck there.

But Jupiter and the other planets will affect these dimples so permanence is no guarantee. Trojans won’t last forever. I think Earth may currently have a short term Trojan.

SOHO orbits L1, so the “dimple” is large enough for it to do so w/o using constant rocket fuel. But it orbits L1 in order to get a clean signal to Earth, otherwise the noisy Sun would drown out the signal.