Sedna, a celestial object located in the outer reach of our solar system, has remained a fascinating and mysterious object in the distant reaches of our solar system since 2003. The celestial body is classified as a trans-Neptunian object (TNO), specifically a distant and highly eccentric Kuiper Belt object, and it was discovered by astronomers Michael E. Brown, Chad Trujillo, and David Rabinowitz.
1. Hidden planet
Twenty years after its discovery, a new study by two Japanese researchers, suggests that a far undetected Earth-like planet could be hovering in that region, deviating orbits of Sedna and a handful of similar TNOs, which are the countless icy bodies orbiting the sun at gigantic distances. Many TNOs have oddly inclined and egg-shaped orbits, possibly suggesting the gravitational pull of a hidden planet, astronomers say.
The newly hypothesized planet was dubbed “Kuiper Belt Planet (KBP)” after scientists used computer simulations to analyze the effects of a potentially undiscovered planet on the TNOs. Those simulations, which included evolutions of numerous real and model TNOs in the furthest reaches of an icy region, known as the Kuiper Belt, produced the extreme orbits observed for Sedna and other TNOs. If KBP orbits within 54 billion km, the authors say there’s a 90% chance of detecting it in the sky.
They also concluded that such a planet would be between 1.5 to 3 times Earth’s size and would reside somewhere between 37 billion km to 74 billion km from the sun. “It is plausible that a primordial planetary body could survive in the distant Kuiper Belt, as many such bodies existed in the early solar system,” researchers write in the new study.
In the past, some astronomers have proposed various theories about Sedna’s origin, including the possibility of a distant, undiscovered massive planet — often referred to as “Planet Nine” — influencing its orbit. However, a 2021 independent study claimed data used by the team behind the discovery paper first theorizing “Planet Nine” was biased, and concluded that there’s a very low chance of such a planet existing.
2. Sedna
As for Sedna’s orbit, it reveals an extremely elongated and highly elliptical orbit that takes it to the most distant reaches of the solar system. Previous research and observations determined the celestial body to be located far beyond the Kuiper Belt and the influence of Neptune. Compared to the major planets in our solar system, Sedna is relatively small, with an estimated diameter of about 995 kilometers, making it significantly smaller than Earth’s Moon and many other objects in the solar system.
