Could ice world in the outer solar system lead the way to Planet Nine?

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A growing number of small, icy worlds discovered in the far reaches of the solar system could lead researchers to the elusive Planet Nine. The latest of these small enigmatic objects, called L91, sweeps so far out that it may take more than 20,000 years to orbit the sun.

Researchers first discovered the object in 2013, but the latest observations of its odd orbit suggest it is being pulled by a huge mass far beyond the sun and the solar systems gas giants.

According to Science magazine, L91’s huge elliptical orbit means the icy world never comes closer than 50 times the distance between Earth and the sun (1 AU) and may swing as far out as 1,430 AUs. Astronomers believe that the strange paths of distant object such as L91 and others, such as Sedna, are affected by the gravitational pull of a dense world far beyond the known eight planets: the as yet unidentified Planet Nine.

A team at the Outer Solar System Origins Survey (Ossos) have been tracking the icy worlds beyond Neptune to study their origin and why they take the paths they do. Presenting their findings this week at a meeting of the American Astronomical Society’s Division for Planetary Science in Pasadena, California, members of the team indicate that L91 is being pulled by a distant object, resulting in its elongated orbit.

Some astronomers believe the effect is caused by the unidentified Planet Nine, reports Nature, but the Ossos team thinks the disturbance could be explained by a passing star, or by the sheer mass of the Milky Way. ‘Every time we find another one of these objects, it adds another piece to the puzzle,’ planetary scientist Meg Schwamb told Nature.