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What is Planet 9: Invisible Monster Planet, a Black Hole or Fiction?

Exoplanet. Representative Image. (Reuters)

Exoplanet. Representative Image. (Reuters)

Recent findings have put a dampener on the search for the mysterious ninth planer of our solar system. But some believe that 'Planet 9' is still out there.

Is it a planet? Is it a black hole? Or is it just an illusion?

The mysterious 'Planet 9' has led to many futile searches over the centuries. Many including astronomers, planetary experts, scientists, and romantics have wracked their brains trying to locate the "planet" at the edge of our solar system. And up till a few years ago, the evidence of the suspected 9th planet was pretty strong.

Recent studies, however, have shown that the existence of Planet 9 and the evidence that supposedly suggested could all just be an illusion. According to recent findings by critics of the theory, the evidence of 'Planet 9' - a clustering of Trans Neptunian Objects (TNO) which was believed to be caused by the presence of the planet - was only visible because the telescope that spotted the cluster just happened to be looking there.

What is 'Planet 9'?


For years, several scientists have tried to prove the existence of the mysterious ninth planet of the Earth's solar system. It is believed to be ten times the mass of Earth and is expected to be made of the same icy stuff that Uranus and Neptune - its closest supposed neighbours - with the same solid core as them. It is located beyond the Kuiper Belt and though no one has seen it, many are convinced of its presence.

When was it 'discovered'?

The quest for a 'Planet X' dates back to the 19th century when businessman and travel writer (the 19th century equivalent of a present-day travel blogger) became convinced that there existed a mysterious ninth planet. In 1930, 14 years after his death, one of his disciples at the observatory he had devoted to unraveling the mysteries of the universe found what was later known as the planet 'pluto'. The celestial body, however, was no 'Planet X' and by 2006, Pluto has dubbed a "Dwarf Planet". The important shift came after the Voyager space mission in 1989 discovered that the shift in the orbits of Uranus and Neptune that Percival Lowell had attributed to the mysterious Planet X was nothing but the result of a miscalculation. The mission further led to the discovery of the Kuiper Belt, opening up a world of what came to be known as 'transneptunian objects' including other dwarf planets. While the discovery proves that Pluto was indeed not Planet X, it did lead to newer discoveries that suggested the presence of a planet - or some other celestial body - beyond the Belt. Some of the dwarf planets were moving in unusual manners and based on their observations, two scientists - Mike Brown and Konstantin Batygin, asserted in 2016 that 'Planet 9' did exist and was 10-times the size of Earth. While both Brown and Batygin insist Planet 9 exists, many scientists have offered other explanations for the gravitational pull experienced by the dwarf planets in the Kuiper belt. These also explain why the 'planet' has not been visible so far as some believe it's not a planet after all.

Planet or a black hole?

One of the most prevalent alternate theories about Planet 9 is that it is not, in fact, a planet but a primordial black hole. Not a supermassive black hole like the one supposedly detected in the centre of the galaxy or even a stellar black hole but a primordial black hole. While the latter is several times bigger than the mass of our sun, a primordial black hole can be the size of a planet and may pass by undetected. Many such as American researcher James Unwin of the University of Illinois believe that it is indeed a primordial black hole that is distorting the orbits of celestial bodies in the Kuiper Belt and thus messing them up in a cluster.

What do recent discoveries say?

The recent study led by Kevin Napier of the University of Michigan found that the cluster of TNOs that Brown and Batygin had identified as being affected by Planet 9's gravitational pull was not indeed in a cluster but only appeared to be so due the location and timing of its viewing. Napier's team studied a sample of 14 TNO's using three tests from different telescopes located in different spots of the world and found that all the TNOs behaved in their normal orbits. The study has been approved of by scientists like astronomer Samantha Lawler of the University of Regina who thinks of the discovery as commendable since it was based on a more 'uniform' basis. Unable to explain the existence of the solar system with the clustered orbits as described by Brown and Batygin, many believe that the study puts a final nail in the coffin.

The search still on?

Planet 9's lead theorizer Batygin has, however, rejected the results of the study and said that the tests employed by Napier's team were not adequate to dismiss and his and Brown's paper. He argued that Napier's paper could not prove if the cluster orbits were indeed clustered or distributed uniformly. Napier has also admitted that though it is unlikely, studying just 14 TNOs is not nearly enough to fully understand what is happening at the edge of our galaxy. Scientists are currently waiting for the new Vera C. Rubin Observatory being built in Chile to answer these questions. The observatory will start functioning by 2023. Until then, believers and non-believers of Planet 9 will just have to agree to disagree.

first published:February 19, 2021, 20:12 IST