Scientists at the University of Arizona’s Lunar and Planetary Laboratory (LPL) say that the behavior of objects in a region of the Kuiper Belt may indicate the presence of an undetected planet-sized object whose mass may be between Earth and Mars. This announcement comes nearly a year and a half after a separate group of scientists working at the California Institute of Technology (Caltech) announced that there may be a “Planet 9” that is ten times the size of Earth lurking in the Kuiper Belt.
The orbits of Kuiper belt objects (KBOs) normally circle the sun at a tilted angle compared to the plane at which the major planets orbit the sun. Sometimes a KBO’s orbit will be disturbed by either collisions with other objects, or the gravitational field of a large enough object like the planet-sized object theorized by the LPL team.
Kat Volk, a postdoctoral fellow at LPL and the lead author of the study, said of the results seen in studies of the region where the unseen “Planet 10” resides, “According to our calculations, something as massive as Mars would be needed to cause the warp that we measured.”
Most Kuiper belt objects reside farther out from the sun than Neptune. To put things in perspective, the “Planet 9” theorized by Caltech may reside between 500 and 700 astronomical units from the sun. Neptune’s average distance from the Sun is 30.1 astronomical units. An astronomical unit is the average distance between the sun and Earth, about 150 million kilometers.
What it amounts to is that scientists have not yet seen the theorized “Planet 9” or “Planet 10” yet, but can measure their gravitational impact on the Kuiper belt. Renu Malhotra, a professor of planetary sciences at LPL who has participated in the study that produced the theory that there is a Mars-sized planet in the Kuiper belt, is confident that the Large Synoptic Survey Telescope (LSST) could assist with the search for new objects in the Kuiper belt when it goes online in Chile. “We expect LSST to bring the number of observed KBOs from currently about 2,000 to 40,000,” she said of the new telescope. It might even be able to spot the theorized planets in the Kuiper belt.
And why aren’t there more planets in the solar system? Well, the current prevailing theory is that the early solar system was a lot like a crazy, complicated billiards game. Earth’s Moon theoretically formed in the aftermath of a collision between Earth and a planetary-sized object of similar size. Some early planets in the solar system could have become victims of gravitational interactions with other planets by being either booted into the sun or booted out of the solar system entirely to become “orphan” planets. These theoretical planets in the Kuiper belt could be survivors of this early billiards game along with the planets (and dwarf planets!) that we are currently familiar with.
It’s unlikely that either theoretical planet in the Kuiper belt will turn out to be the theoretical “Planet X” that doomsday alarmists like to claim is inhabited by ancient, possibly hostile aliens. However, a confirmation of either “Planet 9” or “Planet 10” will be a good step in understanding the mechanics of the Kuiper belt and our solar system as a whole.