For decades now, scientists have been deliberating over the existence of an unknown planet lurking in the far reaches of our Solar System. Over the past decade or so, many became increasingly convinced that it was just a matter of time till someone would furnish conclusive evidence proving that a planet 10-times more massive than Earth orbits the Sun in the outer edges of the Solar System.

evidence supporting Planet Nine

However, a recent study of four large bodies in the outer Solar System seems to have caused a massive setback in the hunt for Planet Nine, as our hypothetical ninth place is popularly known as.

The speculative existence of Planet Nine was basically supported by the fact that the orbits of the distant Trans-Neptunian Objects (TNOs) seemed to be clustered together. Such a cluster formation would not be possible in the absence of a massive object in the vicinity. However, the study that monitored these TNOs now suggests that the clustering is probably not even real and is only a product of detection bias.

However, while the latest survey casts some serious doubt over the existence of a massive planet beyond Neptune, there are still certain anomalies in the orbits of distant TNOs that it can not explain.

Simply put, the orbits of all the known planets of our Solar System are aligned along the same plane known as the invariable plane. Considering that the Solar System as a unit is gravitationally isolated, one would expect the orbits of TNOs to have similar orientations as the planets. Of course, odd deviations would be understandable, but what baffles scientists is that the orbital orientation of most distant TNOs is tilted nearly by eight degrees compared to the invariable plane.

Such deviation can occur only if there is a gravitational tug by a larger body in the neighboring regions. Based on the extent of the tilt, it seems like the hypothetical “Planet Ten” could be similar in size as Mars.

While more data needs to be collected to conclusively prove Planet Ten’s existence (and Planet Nine’s non-existence), astronomers are optimistic that they will be able to crack the mystery in the next few years.

[Original study: Kathryn Volk and Renu Malhotra. The curiously warped mean plane of the Kuiper belt.  arXiv:1704.02444[astro-ph.EP] (2017)]


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