Artist’s impression of a possible ninth planet that might exist in the outer solar system. – CALTECH

Interview by Nicolas BEGASSE

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She did not name yet, and no one is even sure that it does exist. But the calculations of Californian researchers claiming that a ninth planet, larger than Earth, exists in our solar system, are considered seriously by the scientific community. And Alessandro Morbidelli, research director at CNRS established the Observatory of the Côte d’Azur, is no exception. 20 Minutes has requested a connoisseur of the solar system what he thought of the discovery.

This is not new, as a theory, a 9th distant planet …

In 2014, an article had highlighted the fact that the most distant objects in the solar system, 13 in number, have orbits roughly aligned, which is statistically abnormal. Its authors explained by the possible presence of a planet. But they had not demonstrated, and choosing their 13 objects they had just mixed the apples and oranges. The article in this week separates these cloths and the towels, and keeps more than 6 distant objects which, for once, the orbits are really aligned in space. They calculated that the probability that it is due to chance is 0.007%. So they revisited the hypothesis by showing that the planet was solid and characterizing this planet and its orbit.



Why we did not have the idea to do these calculations before?

Because the six distant objects used in the study are not known for a long time, less than ten years for some. So it was necessary to know the time, they and their orbit. And then you had to believe, to engage in such research! Personally, I would have been afraid to give a sword in the water

& gt;. & Gt; TO READ. The hunt for the 9th planet is open

Could we not calculate where the planet is located, to observe it?

We could do it for Neptune : 8th planet was discovered in 1846 by Le Verrier, who inferred its orbit and its position on this orbit because the Uranus-Neptune configuration allow. So, the observation of the planet could be done quickly, because we knew where to look. Here it is different, the type of orbit is understood that the ninth planet but we may not know where she is. It’ll be a very long search: I think it will take between ten and fifteen years to either find or conclude: “It’s weird, but there is no ninth planet”

Why such an expectation?

A new telescope, the OHSA is being built in Chile. It will have a wide field of vision, designed to see the whole sky. If there is something to be found, it will be found with it. It is expected to start around 2022, I give him a little time to work well and look and I can at best possible observation of the ninth planet from 2026.



How planet has she recovered so far from the Sun?

This planet, if it exists, is a byproduct of the formation of giant planets. They were formed from smaller planets, colliding in the early solar system, have accreted. But all have not accreted, some were sent far away as exiles from the center of the solar system. And the orbit of the planets exiled looks quite than the ninth planet. In fact, the planets are born as a family, and as a result fratricide most beefy survive and smaller are either accreted or hunted.



Can we imagine a planet 10th, 11th, 12th …?

No index can think, in May it does not mean there are none. That said, there is a limit to both the number of planets can form a solar system and the number of expelled planets may continue to rotate around the Sun-four out of five will leave the solar system. So I would say that a ninth planet, is likely, perhaps a tenth, but I would not go beyond.

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