No: The ninth planet has not been discovered!

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

24 January 2016

In 1911, Sir Ernest Rutherford proposed a model of the atom in which the motion of electrons was similar to that of planets going round the sun. This came to be popularly known as the nuclear model. Even though the details of the electrons were soon found to be quite inaccurate, the basic structure of a heavy nucleus and tiny particles “whizzing” around it is still accepted by the scientific community to this day.

Rutherford came up with this profound idea after studying data from an experiment that had been done by his students (Geiger and Marsden) a few years earlier (1909). They had found that when a beam of hig-speed charged particles was fired onto an extremely thin gold foil, about one out of 8,000 were scattered backwards.

Now, one out of 8,000 is an extremely small fraction – 0.0125% – but still, Rutherford recognised its importance inasfarus the atom was concerned. He tested the previously accepted atomic model and found that the predicted fraction of back-scattered charged particles was about one in ten-to-the-power-of 3,200; that is, a number with 3,200 zeroes!

It is a similar kind of thinking that has lead a pair of astronomers to predict that there ought to be a ninth planet in the solar system. Now, some media houses reported that the ninth planet had been discovered: that is NOT true. It has NOT been seen yettw.

On studying the motions of the six outermost objects of the solar system, astronomers Konstantin Batygin and Michael Brown found that the orbits cluster together as they come to their points of closest approach to the sun. After doing the (very complex) math, Batygin and Brown established that the probability of that happening completely at random was about one in 15,000 (0.007%)!

That led the pair to seek another explanation apart from a random happenstance. So they tried the possibility of a planet existing in that vicinity. It turned out that the kind of object that explains the observed orbits would be about ten times the mass of the earth and be at least 45 billion kilometres from the Sun. The calculations also predict that such a planet would take about 20,000 years to complete one revolution.

45 billion km is very, very far away! Travelling at 300,000km per second, light from the sun takes almost two days (41 hours) to get there. It is also very cold and very dim. In fact, the estimated brightness of the proposed planet is far below what the most sensitive telescope can see. Chances are that it cannot be seen with current technology!

It is important to emphasise that no planet has been OBSERVED – neither directly through a telescope nor indirectly from gravitational influence of nearby objects. What Batygin and Brown have done is simply given one possible explanation of the orbits of the six outermost objects in the solar system.