Over the last 30 years, scientists have been collecting evidence of the chilling regularity of mass extinctions on Earth. Two researchers now think that the source of the mass extinctions is the hypothesized ninth planet of the Solar System, commonly referred to as “Planet Nine.”
According to retired Professor Daniel Whitmire, the yet undiscovered planet could be the cause of periodic comet showers. This is thought to have occurred because the planet has a slowly rotating orbit. This causes the planet to pass through the Kuiper Belt every 27 million years, which unleashes a swarm of comets towards the inner Solar System.
Apparently a periodicity of mass extinction, every 27 million years was first discovered in 1984 and it has shown to date back 500 million years. Geological records also show that the phenomenon is highly regular, with a variation no larger than 10%.
Planet Nine is the third suggested astronomical model. It was proposed by Whitemire and his colleague John Matese in 1985, and to produce the desired comet shower, the model required the existence of the Kuiper Belt and a gap in material about 7.5 billion kilometres from the Sun. Both the belt and gap were actually discovered a few years after, but Planet Nine was not, meaning the hypothesis remained untested.
However, the more recent discoveries of several large objects in both the Kuiper Bell and the Oort cloud has enabled the scientists to better refine their theory. These objects have a perihelion very near each other, suggesting the presence of a large object more than 10 times the mass of Earth. This is consistent with the hypothesised existence of Planet Nine, suggesting that the objects could be one and the same.