The original search for Pluto was motivated by unexplained orbital motions of Neptune and Uranus, which was assumed to be caused by "Planet X". Neptune had been found by examining the gravitational effect it had on Uranus. Because he was looking for Planet X, and through serendipity, Clyde Tombaugh discovered Pluto in 1930. However, Pluto is not large enough to explain the observed orbital motions. Tombaugh was just lucky. It has been 70 years, and while unlikely, the existence of Planet X is still a possibility.

The first reference to Planet X was made by Percival Lowell, and he dedicated the years from 1909 through 1915 to finding it. This was in the beginning of the 20th century, before Pluto was discovered. Some of the pictures taken from his private observatory even showed Pluto on them !

Then Tombaugh found Pluto, as described in the previous writeup.

In 1977-1984 Charles Kowal performed systematic search for undiscovered bodies in the solar system. During his search, Kowal found 5 comets and 15 asteroids. Kowal also recovered 4 lost comets and one lost asteroid. Kowal did not find a tenth planet, and concluded that there was no unknown planet brighter than 20th magnitude within 3 degrees of the ecliptic. Since then a belt of asteroids, the Kuiper Belt has been found outside of Pluto.

The Pioneer and Voyager spacecrafts has revealed nothing, and nowadays Planet X is just history within astronomy.

There is also a "novel" entitled "Planet X."

It's a Star Trek: The Next Generation/X-Men crossover.

No, I'm not kidding.

Written by Michael Jan Friedman and published in 1998. Apparently it's a sequel to something else, because in this novel the X-Men are already familiar with the crew of the Enterprise. They're pulled from their time, and their universe, seemingly at random, when their timehook goes ka-blooey. While hanging out on the Enterprise, they get the chance to be cosmic do-gooders and help a planet whose inhabitants are beginning to develop mutant powers of their own.

At the risk of editorializing, the book really isn't very good (IMO anyway). It's got the subtle backstory of the X-Men, with the heavy-handed preachiness we've all come to expect from Star Trek. Plus the whole concept is just plain silly.

There are worse ways to waste a couple hours than poring over its 265 pages, but I'm having a bit of trouble thinking what they might be right now.

A theory that suggests the existence of an earth-risking large planet (or a dead star) which orbits the sun and is yet to be seen. The supporters of the theory argue about a scenario aimed for May 15, 2003, in which it will get close to Earth and cause great devastation.

In this scenario, its magnetic force will stop the Earth rotating for several days; it will cause huge earthquakes, volcanoes, Tsunamis and hurricanes all over the planet. Crops will fail, millions will stave. 90% of the planet's population will die. The force of its passing will cause the Earth's magnetic poles to shift.

It is not really a planet, actually a brown dwarf; a small, failed star. They give it a size of 4x that of Earth, and a density of 20x. It orbits the Sun and also a second star in our solar system that possibly exists. It travels very quickly when it passes close to either star, but slowly in between. This acceleration is caused by gravity and is exactly the sort of thing you see with comets.

NASA claims they have no evidence for it existing, but admit it is possible. The Planet X scenario requires a large planet, which we would have seen Planet X if it were anywhere near Earth. Instead, they argue that it is normally travelling slowly, a vast distance away.

Dr. John Murray, of the UK's Open University, claims he has found a 10th planet 30,000 times the distance from the sun that Earth is - 3,000 billion miles away. By analysing the orbits of comets, the claims to have 'pretty conclusive' evidence for another planet. He has calculated that there is a 1/1700 chance of there not being a 10th planet. They also give it a mass of between 1 and 10 times that of Jupiter's, which fits nicely with the Planet X scenario. They say it could be a brown dwarf, which is what many people believe the Planet X is.

Unfortunately, for the Planet X theorists, he gives it an orbit time of 6 million years - not the 3,600 required for their scenario. This means that this 'Planet X' is not the one predicted to devastate the Earth in 2003. They also have not given it the extremely elliptical orbit required for it to pass close to Earth.

The normal way in which planets are discovered is by looking at the orbits of other planets. As planets have gravity, they affect the orbits of all the others. For decades, people have claimed that the orbits of the three outermost planets, Uranus, Neptune and Pluto are 'wrong' - that something else is influencing their orbits - another planet.

The IRAS (Infrared Astronomical Satellite) is a space telescope that has survey the sky. This is what Gerry Neugebauer, chief IRAS scientist, had to say, in 1982:

"A heavenly body possibly as large as the giant planet Jupiter and possibly so close to Earth that it would be part of this solar system has been found in the direction of the constellation Orion by an orbiting telescope. All I can tell you is that we don't know what it is". Since then, NASA has denied the existence of the planet and claimed that the orbits of the outer planets are in fact correct.

Planet X was probably first recorded by a civilisation called the Sumerians, who were around about 6,000 years ago. They called it 'Nibiru', meaning 'Planet of the Crossing'. They suggested it had a 3,600 year orbit. You may be wondering why so many people are putting so much faith in the observations of civilisation that lived thousands of years before telescopes and computers. The answer is that the Sumerians were incredibly advanced scientifically, correctly calculating the orbits of many planets in our solar system.

In June 2003, they say Planet X will finally start to near Earth after it's 3,600 year orbit, passing just 14,000,000 miles from Earth. It would definitely exert a gravitational force on the Earth, but they also say there would be a magnetic force, what they call 'repulsion force'.

As the planet passes these two forces will be opposite to those acting on the Earth from the sun. This would leave Earth as the rope in a tug of war game between the two. This would make the Earth's core, which is the magnetic part, rotate. However, the crust, which is not magnetic, would not be affected. This would make the core rotate, changing the position of the Earth's magnetic poles. This would set off virtually every volcano on Earth and choke the atmosphere with so much ash the sun would be blotted out.

These forces on the Earth would also be so great that the Earth would stop rotating for three days, leaving half of the Earth in darkness and half in day. However this would be gradual - or else no one would survive. For this to be true you would expect a slowing of the Earth already.

If changes this severe were caused by Planet X, and this is approaching, we would expect to see more earthquakes and a slowing Earth already.

Here is a distance table compiled by Zetatalk, a pro-Planet X website: (The speed column on the right was calculated from their data).

Date      Distance (mile*10^9)  Speed (mile/hour)
11/7/99	  34.216                     
2/7/00	  34.166                11447     
5/7/00	  34.09                 17399
8/7/00	  33.974                26557
11/7/00	  33.797                40522
2/7/01	  33.528                61584
5/7/01	  33.119	        93636
8/7/01	  32.495	        142857
11/7/01	  31.547		217033              
2/7/02	  30.103		330586              
5/7/02	  27.904	   	503434                       
8/7/02	  24.558                766026
11/7/02	  19.464	        1166209
2/7/03    11.71	                2831580          
3/2/03	  9.1665	        1892485    
4/2/03	  5.0412	        3664979     
4/16/03	  3.0865	        3878373    
4/23/03	  2.06	                3055060   
4/30/03	  1.216	                2511905
5/7/03	  -0.0929	        7791071

The data shows how the planet would speed up very rapidly when it neared our sun, which would explain why we cannot yet see it.

However, there is a problem with these figures: when it passes through the inner solar system it will have a speed of about 7.8 million miles per hour, check this if you want. At the surface of the sun the escape velocity for our solar system is just 1.3 million miles per hour. This means that if Planet X passed through at that speed it would simply fly out, never to be seen again.

Summarized, edited and E2-proofed from:

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