New evidence for Planet 9 at the edge of our solar system

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New findings strongly suggest the existence of a Planet 9 at the edge of our solar system. Image via Solen Feyissa/Unsplash.

New evidence for Planet 9

There is growing evidence that a planet the size of Neptune – Planet 9 – is hiding deep at the edge of our solar system. Researchers from Caltech, Université Côte d’Azur and Southwest Research Institute published a pre-print article on April 17, 2024. In it, they argue that a group of small bodies beyond Neptune are clustering together due to Planet 9’s gravitational influence. These distant bodies in the solar system are not evenly distributed in their orbit like the boulders of the asteroid belt. Instead, they form clumpy groups. So the researchers believe that a larger, more distant object is forcing them into this pattern through gravity. And in fact, this is how Planet Eight – Neptune – was discovered. Neptune moved in the orbit of Uranus.

Two of the new paper’s four authors, Konstantin Batygin and Mike Brown of Caltech, are the founders of the Planet 9 theory. In fact, Mike Brown wrote a book about his life and research at the far edge of our solar system: including the reclassification of Pluto. The book is titled “How I Killed Pluto and Why It Had It Coming.” But these researchers believe there is an object much larger than Pluto further out in our solar environment. This planet would be the size of five Earths (about the size of Neptune) and 400 to 800 times further from the Sun than Earth.

The astrophysical diary letters has accepted the article for publication. There is no peer review yet. A copy of the paper is available on arXiv.

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Batygin on the Event Horizon podcast

Batygin said on John Michael Godier’s Event Horizon podcast that this was the case:

…the fifth and most statistically significant piece of evidence we have so far for the existence of Planet 9.

Batygin also said:

What we have examined in this article is a population of trans-Neptunian objects that we had previously ignored. These are populations of long-period icy, asteroid-like objects that normally live beyond Neptune’s orbit… but whose orbits intersect Neptune’s. We also specifically looked at the population of Neptune cruisers that live near the plane of the solar system.

So since the objects cross Neptune’s orbit and are pushed around by the giant planet, they would have scattered if left alone. As Batygin said:

The fact that we see them at all requires some form of gravitational influence. …What we show in this work is that not only is Planet 9 up to the task, but also that Planet 9’s predicted orbit distribution matches perfectly with what we see in the data.

In fact, Batygin said that a solar system without Planet 9 could be ruled out with a certainty of five sigma. This value is considered sufficient for fields such as particle physics to declare a discovery. It is a “gold standard” that corresponds to about a one in a million chance that the result was due to chance.

Planet 9, galactic flood or black hole?

Are there any other theories besides Planet 9 that could explain the accumulation of trans-Neptunian objects? One of these theories concerns the galactic flood. And the researchers studied this attraction of the galaxy itself. However, they found that some features of the distribution of objects cannot be reproduced with the galactic tide. However, the Planet 9 theory was a perfect fit.

Another theory, not discussed in the paper, is that Planet 9 could be a black hole instead. If there are black holes far out in the distant solar system, Harvard astronomer Avi Loeb has suggested a way to look for them. They would look for flares created by encounters between black holes and small, distant objects.

The upcoming Vera Rubin Observatory could be just the right tool to provide the crucial data to solve the mystery of Planet 9, or black holes in the solar system. The telescope is expected to be operational in early 2025.

Unfortunately, the new data from the latest study doesn’t help us find the direction to point our telescopes on Planet 9. So the hunt continues.

Announcement on social media

Here’s how lead author Konstantin Batygin announced the discovery on social media:

Conclusion: Researchers said that the cluster of small objects outside Neptune’s orbit is perfectly consistent with the existence of a Planet 9 hiding on the edge of our solar system.

Source: Generation of low-inclination TNOs and Neptune transit by Planet Nine

About Event Horizon

Kelly Kizer Whitt

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About the author:

Kelly Kizer Whitt has been a science journalist specializing in astronomy for more than two decades. She began her career at Astronomy Magazine and has been a regular contributor to AstronomyToday and the Sierra Club, among others. Her children’s picture book “Solar System Forecast” was published in 2012. She has also written a dystopian young adult novel called A Different Sky. When she’s not reading or writing about astronomy and stargazing, she enjoys traveling to national parks, doing crossword puzzles, running, playing tennis, and paddleboarding. Kelly lives in Wisconsin.

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