Is a massive, undiscovered world lurking in the far reaches of our solar system?
In short: Astronomers have long theorized that a giant planet, nicknamed Planet Nine, might be hiding far beyond Pluto. While we have not yet seen it, the strange, clustered orbits of distant icy objects in the Kuiper Belt suggest a massive gravitational presence is tugging on them from the dark.
The hypothesis for Planet Nine, proposed by Caltech astronomers Konstantin Batygin and Mike Brown in 2016, rests on gravitational patterns rather than direct observation. They noticed that certain small, icy objects in the Kuiper Belt follow unusually aligned, clustered orbits. To explain this, they proposed a Neptune-sized world with a mass roughly 5 to 10 times that of Earth, orbiting the Sun on a highly elongated path. This theory follows a long history of searching for unseen worlds, including Percival Lowell's 1915 hypothesis regarding a planet named 'Planet X.' While Lowell's specific prediction was eventually proven wrong, his work indirectly led to the 1930 discovery of Pluto.
This hypothetical planet would be incredibly distant, orbiting about 20 to 30 times farther from the Sun than Neptune, on average. A solitary revolution spans roughly 10,000 to 20,000 Earth years. Because it is so far away, the planet's reflected sunlight becomes incredibly faint, making it notoriously difficult to detect with traditional visible-light telescopes. The sheer scale of this potential world is staggering. If it exists, it could be approximately 1.5 times the size of Earth.
The search has recently taken a new direction. Researchers Terry Long Phan and Tomotsugu Goto analyzed archival infrared data from the 1983 IRAS satellite and the 2006 AKARI satellite. By looking for the planet's intrinsic infrared glow, they identified a single candidate pair of light dots that could represent a moving object. However, the scientific community remains skeptical. Some experts argue the signal may not survive follow-up observations, and Mike Brown has noted that if the signal is real, it might represent a different object entirely, rather than the specific Planet Nine predicted in 2016. The researchers narrowed down an initial catalog of roughly 2 million objects to find their candidate. This process involved removing known stars and noise from the galactic center to isolate the potential signal.
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Sources
- Summary by Intellect · source: Mike Brown: The search for our solar system's ninth planet
- Also: Hypothetical Planet X
- Also: Astronomers searching for Planet Nine find possible hints of different planet | Science | AAAS
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