Whitmire's new research, published in the January issue of Monthly Notices of the Royal Astronomical Society, says that as yet undiscovered “Planet X” triggers comet showers linked to mass extinctions on Earth at intervals of approximately 27 million years.
Whitmire and his colleague, John Matese, first published research on the connection between Planet X and mass extinctions in the journal Nature in 1985 while working as astrophysicists at the University of Louisiana at Lafayette. Their work was featured in a 1985 Time magazine cover story titled, “Did Comets Kill the Dinosaurs? A Bold New Theory About Mass Extinctions.” At the time, there were three explanations proposed to explain the regular comet showers: Planet X, the existence of a sister star to the Sun, and vertical oscillations of the Sun as it orbits the galaxy. The last two ideas have subsequently been ruled out as inconsistent with the paleontological record. Only Planet X remained as a viable theory, and it is now gaining renewed attention.
Whitemire and Matese’s theory is that as Planet X orbits the Sun, its tilted orbit slowly rotates and Planet X passes through the Kuiper belt of comets every 27 million years, knocking comets into the inner solar system. The dislodged comets not only smash into the Earth, they also disintegrate in the inner solar system as they get nearer to the Sun, reducing the amount of sunlight that reaches the Earth.
Whitmire says what’s really exciting is the possibility that a distant planet may have had a significant influence on the evolution of life on Earth.