# New Planet-oid found



## Ice fyre (Mar 27, 2014)

What is quite remarkable about this is that there are indications that there could be a massive planet kicking around out there on the fringes of our Solar system. 
Dwarf planet discovery hints at a hidden Super Earth in solar system | Science | The Guardian


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## kythe (Mar 27, 2014)

It's an interesting hypothesis that there could be another planet out there.  But I have a couple of questions, if anyone here is good with astronomy.

1.  When I was a kid, there was a theory that there was another large planet beyond Pluto that was pulling on the other planets.  I think it was based on the idea that the orbits didn't fit a mathematical model of a 9 planet (including Pluto) solar system.  But that theory was scrapped when it was discovered that the original mathematics were wrong.  How do we know they have calculated correctly this time?

2.  Some telescopes are so powerful planets have been discovered orbiting distant stars.  Scientists are even able to determine the size and composition of some of these planets.  So why don't we yet know our own solar system completely?


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## Brian G Turner (Mar 27, 2014)

Ice fyre said:


> What is quite remarkable about this is that there are indications that there could be a massive planet kicking around out there on the fringes of our Solar system.
> Dwarf planet discovery hints at a hidden Super Earth in solar system | Science | The Guardian





kythe said:


> It's an interesting hypothesis that there could be another planet out there.  But I have a couple of questions, if anyone here is good with astronomy.
> 
> 1.  When I was a kid, there was a theory that there was another large planet beyond Pluto that was pulling on the other planets.  I think it was based on the idea that the orbits didn't fit a mathematical model of a 9 planet (including Pluto) solar system.  But that theory was scrapped when it was discovered that the original mathematics were wrong.  How do we know they have calculated correctly this time?
> 
> 2.  Some telescopes are so powerful planets have been discovered orbiting distant stars.  Scientists are even able to determine the size and composition of some of these planets.  So why don't we yet know our own solar system completely?



This is all very interesting - it's long been considered that a larger and as yet undetected planet may exist on the fringes of the solar system - it has the working title name of "Nemesis".

It was first postulated due to the strange orbits of the outer planets - the idea was floated that another larger planet may be influencing then. If I recall correctly, Pluto was found because of that search.

There is a more modern theory that suggests Nemesis may actually be a brown dwarf:
Nemesis (hypothetical star) - Wikipedia, the free encyclopedia

The problem with planet detection - and why it's different to the search for extra-solar planets - is that objects within our solar system have to be directly spotted.

Extra-solar planets, on the other hand, are deduced by examining slight but regular changes in the light from other stars.

The problem for us is that if Nemesis exists, and it is a brown dwarf, it's going to be very hard to spot visually - it would have a very low albedo (ie, reflect little of the sun's light) so would be hard to see with a telescope.

I've personally always been a fan of this idea - a large mass planet with a low reflective index orbiting out sun on a very long ellipse. It's entirely feasible, but is going to be hard to pin down - hence why looking at the movements of other bodies in the Oort Cloud might provide clues.

The problem is that the whole idea has been almost entirely hijacked by the idea of "Nibaru" - basically, an American "psychic" claimed there was a planet on the edge of our solar system, populated by aliens (lizards?) and would come crashing into earth in the early 2000's. The idea spread - the New Age websites tend to act like a big echo chamber for fringe ideas. When it didn't appear, the person in question simply dismissed it - the aliens had said it was just a "test" - but it'll appear later.


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## Mirannan (Mar 27, 2014)

Yup, objects in the outer solar system have to be spotted visually - and there isn't much light to be reflected, and what light is reflected is spread out over a large area of space so we don't get to see much of it. Which means using large telescopes to find the things - and such equipment has an awfully large number of other uses.

I haven't actually thought about this before, but IMHO the brightness of an object at large distance from Earth is probably inversely proportional to the fourth power of its distance - inverse square law twice. (Given constant albedo, natch.)

There is another problem. Very distant objects move very slowly; again, doubly so because their actual velocity is lower (inverse 5/2 power, I think) and because the angular velocity imparted by a given velocity is inversely proportional to the distance from us, assuming it's moving at right angles to the line of sight. This means that the displacement in a given time is going to be smaller the further it is away, making the object's movement on the sky slower (I think inverse 7/2 power) the further away it is.

At some point, such an object is going to be visually indistinguishable from a star at much longer distance - because stars at several lightyears away move much faster than a solar system body is going to if it's way out there. Where that point is, I don't know - maybe if there's an astronomer in the house... ?


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## Dozmonic (Mar 27, 2014)

I only know of this from the Sitchin type hypothesis of Nibiru and the work of people like Jason Martell and others I can't remember. The evidence they pointed to for another body was the eccentricities of Uranus and Pluto's orbits in respect to the plane of planetary orbits. There was a guy whose book I read that talked about the possibility of a brown dwarf out there. All fascinating stuff if you ask me!


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## Mirannan (Mar 28, 2014)

I rather liked the idea casually thrown into Clarke's 3001 - that, sometime in the third millennium, someone set up a bomb-pumped microwave generator (serious bomb - around a gigaton!) somewhere between Jupiter and Saturn, and also a heck of a lot of a lot of microwave receivers, and set it off. The idea being to get a radar snapshot of EVERYTHING in the Solar System.

No idea whether it would work, but sounds cool. There's an awful lot of space under Sol's influence, and something relatively small would take a long time to find.


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## Aquilonian (Mar 29, 2014)

On a related subject- are there really mathematical/astronomical reasons why a "counter-earth" (ie an earth-sized planet in the same orbit but 180 degrees away on the far side of the sun) could not exist?


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## Mirannan (Mar 29, 2014)

Aquilonian said:


> On a related subject- are there really mathematical/astronomical reasons why a "counter-earth" (ie an earth-sized planet in the same orbit but 180 degrees away on the far side of the sun) could not exist?



Yup. Simply put; although such a planet might be possible for a short while, such a position is unstable. Perturbations from the other planets would move it out of position in short order.


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## ralphkern (Mar 30, 2014)

Planets are, in most models, formed out of what's called an accretion disk. A ring of dust and debris that circles a star. It slowly, over millions of years gathers into a single body. Effectively this body 'hoovers' up the rest of the dust in its ring as it forms making shared planetary orbits virtually impossible by formation. (I say virtually as it's a big universe)

This is why the inner worlds are metal heavy whilst the outer are gassy as the different debris types themselves will migrate to more stable orbits. (Or be ejected from the system or fall into the star)

There are other ways that a planet could get there, through migration or capture.

There are some stranger system geographies however, for example in many systems where Exo planets have been found, they are VERY close to the parent star.

55 cancri E, for example, a world 8 times the mass of Earth, is so close it orbits it's star every 18 hours...

And it's made of about a third diamond.


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