New planet in the solar system-Planet-X !!

The artistic rendering showing the distant view from Planet Nine back towards the sun. (Source: Caltech/R. Hurt)

The solar system appears to have a new ninth planet. Two well known researchers from the California Institute of Technology, Mike Brown and Konstantin Batygin have found evidences in the outer solar system of an object that could be a real ninth planet, Plant-X.

This January, these two scientists announced evidence that a body nearly the size of Neptune (but to be seen yet) orbits the sun every 15,000 years. Their argument is that during the solar system’s beginning 4.5 billion years ago, the giant planet was knocked out of the planet-forming region near the sun. It slowed down by gas and settled into a distant elliptical orbit, where it still lurks today. But still this planet is invisible, might be because it orbits far out from the Sun on a highly elliptical path.

What is the argument?

The entire argument about the existence of Planet X is a theoretical one, based on mathematical models and computer simulations made from six previously known Kuiper Belt objects that orbit beyond Neptune. Kuiper belt is the region of small icy worlds that begins at Neptune’s edge about 30 AU. Movements of these objects  show signs that they’ve been affected by something large.

Brown and Batygin took a close look at six of these worlds and determined that these objects all have orbits that take them within the same area near the Sun. Their orbits clustered in a way that could not occur simply by chance They say there’s only a 0.007% chance (1 in 15,000) that the clustering could be a coincidence. Then they simulated the outer solar system and tried to figure out how to generate the observed patterns. The only reasonable explanation for this grouping of the orbits, is that there's some massive distant Planet Nine which is keeping them together.

This is really a gravitational signature of Planet Nine and that signature is seen in the most distant orbits beyond the orbit of Neptune (the Kuiper belt). Mike Brown and Konstantin Batygin argue that Planet Nine should have a mass about 10 times that of Earth, and an orbit about 20 times farther from the sun than that of Neptune.

Closest approach of this planet to the sun is seven times farther than Neptune, or 200 astronomical units (AUs). An AU is the distance between Earth and the sun, about 150 million kilometers. The Planet X could roam as far as 600 to 1200 AU, well beyond the Kuiper belt. “This is the reason why it took so long to realize it was there,” Brown says. 
But Brown knows that no one will really believe in the discovery until Planet X itself appears within a telescope viewfinder. “Until there’s a direct detection, it’s a hypothesis” he says.

How it started ?

Brown got the first hint of his current quarry in 2003, when he and his team discovered Sedna, the most distant known object in the solar system at the time. Its perihelion (closest point to the sun) lay at 76 AU, beyond the Kuiper belt and far outside the influence of Neptune’s gravity. This means something massive, well beyond Neptune, must have pulled Sedna into its distant orbit. This massive object could be a star, or one of the many other stellar nurseries that surrounded the nascent sun at the time of the solar system’s formation.

Since then, a handful of other icy objects have turned up in similar orbits. By combining Sedna with five other weirdos, Brown concluded, only a planet could explain such strange orbits.

For years, Sedna was a lone clue to a perturbation from beyond Neptune. Then, in 2014, Scott Sheppard and Chad Trujillo published a paper describing the discovery of VP113, another object that never comes close to the sun. They began to examine the orbits of the two objects along with 10 other odd objects. They noticed that, at perihelion, all came very near the plane of solar system in which Earth orbits (called the ecliptic). They raised the possibility that a distant large planet had herded the objects near the ecliptic. But they didn’t press the result any further.

Later that year, Batygin and Brown began discussing the results. Plotting the orbits of the distant objects, they realized that the pattern that Sheppard and Trujillo had noticed “was only half of the story.” Not only were the objects near the ecliptic at perihelia, but their perihelia were physically clustered in space.

After a long calculation and model discussion, a favored size for Planet X emerged, between five and 15 Earth masses, as well as a preferred orbit.

Few complications and Questions !

Even if Batygin and Brown can convince other astronomers that Planet X exists, they face another challenge, explaining how it ended up so far from the sun. At such distances, the protoplanetary disk of dust and gas were likely to be too thin to fuel planet growth. And even if Planet X did exist, it would have moved too slowly in its vast orbit to hoover up enough material to become a giant one.

Instead, Batygin and Brown propose that Planet X formed much closer to the sun, alongside Jupiter, Saturn, Uranus, and Neptune, but got booted outward by a gravitational kick from another gas giant.

It’s harder to explain why Planet X didn’t either loop back around to where it started or leave the solar system entirely. But Batygin says that residual gas in the protoplanetary disk might have exerted enough drag to slow the planet just enough to settle into a distant orbit and remain in the solar system. This ejection might have taken place when the solar system was between 3 million and 10 million years old.

Some researchers consider this as a low-probability event.” Other researchers are more positive. While some say, the probability better than flipping a coin, Some think that it’s exciting.

One considerable fact that strengthens their argument is that the planet Neptune was originally detected in a similar fashion, by researching the observed anomalies in the movement of Uranus.

Spotting the Planet-X

All this means that Planet X will remain in limbo until it is actually found. But spotting the new planet won’t be easy. Because objects in highly elliptical orbits move fastest when they are close to the sun. So, Planet X spends very little time at 200 AU. And if it were there right now, it would be so bright that astronomers probably would have already spotted it.

Instead, Planet X is likely to spend most of its time near aphelion, slowly trotting along at distances between 600 and 1200 AU.

Batygin and Brown are using Subaru telescope to look for Planet X. Brown says it will take about 5 years for the two teams to search most of the area where Planet X could be lurking.

But until the planet is actually seen, its existence is no more than an exciting idea. And ideas aren't always permanent.