Is There New Evidence for a 9th Planet - Planet X?

This week Discover magazine looks at evidence — both old and new — for a ninth planet in our solar system:

'Orbits of the most distant small bodies — comets or asteroids — seem to be clustered on one half or one side of the solar system,' says Amir Siraj [an astrophysicist with Princeton University]. 'That's very weird and something that can't be explained by our current understanding of the solar system.' A 2014 study in Nature first noted these orbits. A 2021 study in The Astronomical Journal examined the clustering in the orbit and concluded that 'Planet Nine' was likely closer and brighter than expected.

Astrophysicists don't agree whether the clustering in the orbit is a real effect. Some have argued it is biased because the view that scientists currently have is limited, Siraj says. 'This debate for the last decade has a lot of scientists confused, including myself. I decided to look at the problem from scratch,' he says.

In a 2024 paper, Siraj and his co-authors ran simulations of the solar system, including an extra planet beyond Neptune. 'We did it 300 times, about 2.5 times more than what was done previously,' Siraj says. 'In each simulation, you try different parameters for the extra planet. A different mass, a different tilt, a different shape of the orbit. You run these for millions of years, and then you compare the distribution to what we see in our solar system....' They found that the perimeters for this possible planet were different than what has been previously discussed in the scientific literature, and they supported the possibility of an unseen planet beyond Neptune.

Scientists hope a new telescope will have the potential to see deeper into the solar system. In 2025, the Vera C. Rubin Observatory on Cerro Pachón — a mountain in Chile, is expected to go online. The observatory boasts that in the time it takes a person to open up their phone and pose for a selfie, their new telescope will be able to snap an image of 100,000 galaxies, many of which have never been seen by scientists. The telescope will have the largest digital camera ever built, the LSST. Siraj says he expects it will take 'the deepest, all-sky survey that humanity has ever conducted.' So, what might the Rubin Observatory find past Neptune? Based on the current literature, Siraj sees a few possibilities. One is that the Rubin Observatory, with its increased capabilities, might be able to see a planet beyond Neptune... 'Next year is going to be an enormous year for solar system science,' he says.

NASA points out that the Hawaii-based Keck and Subaru telescopes are also searching for Planet X, while 'a NASA-funded citizen science project called Backyard Worlds: Planet 9, encourages the public to help search using images captured by NASA's Wide-field Infrared Survey Explorer (WISE) mission.

And starting next year the Rubin observatory will also 'search for more Kuiper Belt objects. If the orbits of these objects are systematically aligned with each other, it may give more evidence for the existence of Planet X (Planet Nine), or at least help astronomers know where to search for it.

'Another possibility is that Planet X (Planet Nine) does not exist at all. Some researchers suggest the unusual orbit of those Kuiper Belt objects can be explained by their random distribution.'

Thanks to long-time Slashdot reader Tablizer for sharing the news.

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