Our Solar System is a bustling cosmic neighborhood filled with planets, moons, comets, and asteroids. New discoveries, often small asteroids or zippy comets, are constantly expanding our map of the solar system.

While the eight main planets were identified by 1846, the search for more continues. Over the past century, we've discovered smaller, distant objects called dwarf planets, the category Pluto now falls under. These discoveries hint at a potential hidden resident in the solar system's outskirts.

The Mystery of Planet Nine

There's a compelling reason astronomers dedicate so much time to finding this elusive ninth planet, nicknamed "Planet Nine" or "Planet X." Our current understanding of the solar system seems incomplete without it.

Gravity, a force exerted by all objects with mass, dictates how objects move within the solar system. The more massive an object, the stronger its gravitational pull. The Sun's immense gravity is why planets orbit it.

Understanding gravity provides the biggest clue for a possible Planet Nine.

Unexpected Orbits

The orbits of distant objects beyond Pluto, like dwarf planets, are puzzling. They travel on elongated, oval-shaped paths, clump together, and tilt compared to the rest of the solar system.

Computer models suggest that a planet ten times Earth's mass would be needed to explain these unusual movements. This is exciting, but where is this planet?

A predicted consequence of Planet Nine is that a second set of confined objects should also exist. These objects are forced into positions at right angles to Planet Nine and into orbits that are perpendicular to the plane of the solar system. Five known objects (blue) fit this prediction precisely.

The Search Continues

Scientists worldwide have been searching for visual evidence of Planet Nine for years. Based on models, it's likely 20 times farther from the Sun than Neptune. Our detection relies on reflected sunlight, similar to how the Moon shines.

However, Planet Nine's immense distance makes it incredibly faint, a challenge even for the most powerful telescopes. Additionally, observing windows are limited. We require moonless nights with our telescopes pointed at the right region of the sky.

Despite the difficulties, hope persists. New telescopes and sky surveys planned for the next decade might hold the key to finally proving or disproving the existence of Planet Nine.

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