What do you mean by neptune is periodically the farthest planet in the solar system because pluto has an eccentri orbit?

Any professional astronomer or astro club.

Nibiru is a mythical planet, sometimes called planet X, based on the old idea that irregularities in the orbits of the outer known planets could only be explained by the existence of a further, large, undiscovered planet.

However this idea, which started in the 19th Century, lost credence when it was found that the supposed irregularities were simply due to miscalculation of the real mass of Neptune.

Then when small objects began to be discovered in the Kuiper Belt beyond Neptune, the idea of Planet X reappeared. One of these objects was Eris, a bit smaller than Pluto, and too small to be a Planet X.

Modern telescopes and techniques have now all but ruled out the idea that Planet X exists.

Edit:Update: Using the latest sensitive observations NASA has discussed the possible existence of a "super-earth" very very far out in an extreme orbit. They have not found it, but say that the orbits of objects beyond the Kuiper Belt seem to suggest its existence.

http://www.news.com.au/technology/science/space/nasa-admits-the-mysterious-planet-nine-is-real-but-says-deadly-nibiru-is-a-f raud/news-story/5037076a579e7e5c642396d307b6aeee

However the idea of a Planet X, or Nibiru, crashing into Earth, has again been dismissed.

according to current discovery (Neptune, Pluto & Uranus) are not planet but let me know according to indian astrology there are 9 planet but the planet which has been discovered as non planet by nasa is there anything writen anywhere that astrologers are talking about the planet among 9 planet is that the same planet which the nasa is talking about and also would like to make you aware that space craft known as puspak viman has been discovered where in india more that 5000 b.c that simply mean that we indian are more advance as per current technologies so definitely our ancient scientist who were called (Rissi) were aware of this discovery before and even though if they have describe about 9 planet that means 9 planet do exist and our current scientist and nasa had not yeat discovered it.

It's behind you

In a word, gravity. The solar system is thought to have formed from a rotating disk of dust and gas with clumps in it. As these contracted the whirling sped up, like a skater drawing in her arms.

There is a law called the conservation of momentum which meant that when planets eventually pulled together in lumps, due to gravity, the spinning of each, and the spinning around the Sun, stayed on.

The Sun has held all this activity to itself in orbit by its massive gravity, which is still felt way out past Pluto.

Never. It will always be the eighth planet (unless an impact by a large celestial body, possibly from the Kuiper Belt, knocks it closer to the Sun) as Pluto is not a planet.

How Long hat's almost 165 times longer than Earth takes to orbit the Sun. ...The Planets in Our Solar System in Order of Size ·Does it Take Neptune to Orbit the Sun

Neptune didn't fully account for Uranus's orbital perturbations so there had to be something else out there.

In our solar system:

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto*

For several reasons including size and eccentric orbit. For a good look at the history of the decision and the reasons behind it, see the book "How I Killed Pluto And Why It Had It Coming" by Mike Brown.