Central Idea

Two Japanese astronomers have uncovered potential evidence of an “Earth-like planet” within our solar system.
This mysterious planet is believed to have resided in the Kuiper Belt, a circumstellar disk beyond Neptune’s orbit that consists of outer solar system objects.
The Kuiper Belt, like the planets, orbits the Sun.

What is the Kuiper Belt?

The Kuiper Belt, also known as the Edgeworth-Kuiper belt, is a flat ring of small icy bodies orbiting the Sun beyond Neptune’s orbit.
Gerard Kuiper, a Dutch-American astronomer, first hypothesized its existence in the 1950s.
This belt contains millions of icy objects, collectively referred to as Kuiper Belt objects (KBOs) or trans-Neptunian objects (TNOs).
It is considered a remnant from the early history of our solar system.
The Kuiper Belt is thought to be the source of many short-period comets that orbit the Sun in less than 20 years.
It primarily consists of small icy bodies, including dwarf planets, asteroids, and comets.
Pluto, once classified as the ninth planet, is one of the most well-known objects in the Kuiper Belt but was reclassified as a dwarf planet by the International Astronomical Union (IAU) in 2006, partly due to its location within this belt.

The Japanese researchers suggest that if this new planet exists, it would be 1.5 to 3 times the size of Earth.
The discovery challenges previous theories of a distant “Planet Nine” and posits the possibility of a planet closer to us, within the Kuiper Belt.
The astronomers predict the existence of an Earth-like planet and several trans-Neptunian objects (TNOs) on unique orbits that could serve as observational signatures of this potential planet’s perturbations.
They estimate that this planet could be situated between 200 and 500 astronomical units (AU) from the Sun, tilted about 30 degrees. For reference, Pluto is 39 AU from Earth.