In 2006, Pluto, believed for decades to be the ninth planet of our solar system, suffered the humiliation of being downgraded to a dwarf planet. Pluto was originally discovered back in 1930. In that year, H.P. Lovecraft began to publish most of the sonnets that would later comprise his book of poetry, Fungi from Yuggoth. He also published his excellent The Whisperer in Darkness, in 1931. That story told of the depredations of a colony of extraterrestrials from the ninth planet, the fictional Yuggoth.
Many assumed that the world of Yuggoth was modeled on the recently discovered Pluto. Alas, most of a century later the cold dark world was reclassified, and so by implication was Yuggoth. So the search for extreme trans-Neptunian objects, a few of which may turn out to be bona fide planets, continues.
Newly discovered bodies in the solar system must meet certain criteria to be labeled as planets: the nominee must first orbit the sun, it must have sufficient size, mass and gravitational force to form itself into a sphere, and it must have enough gravitational force to either absorb nearby asteroids and debris or fling them out of its orbital path—that is, it must not share its orbit with another body. These criteria were developed by the International Astronomical Union in 2006. Pluto failed the third test; it shares its orbit with other objects in the Kuiper belt, and comes perilously close to Neptune’s orbit. (This July, NASA’s New Horizon spacecraft will swing by Pluto for a close look.)
Pluto joins four other objects now officially classified as dwarf planets: Ceres. Haumea, Makemake, and Eris. But there may be hundreds more, especially further out in the Kuiper belt, a disk-shaped region of the solar system composed of comets, asteroids, icy debris, and planet-like objects that extends beyond the orbit of Neptune. Comets that pass by Earth every 200 years or less, for example Halley’s Comet, are thought to originate in the Kuiper belt, sometimes referred to as the “comet belt”.
This week brought news of the possible discovery of two new planets, larger than Earth, in this region of the solar system. These are “ETNOs”, or extreme trans-Neptunian objects. Because they are invisible to direct observation with current instruments, their presence is detected through anomalies in their orbits and those of surrounding objects. This effect is explained as the “Kozai mechanism”, in which a large body gravitationally disturbs the orbit of smaller, more distant objects.
One scientist described this as observing a collection of asteroids in a stable orbit being “shepherded” by a distant, unknown planet of considerable magnitude. Whether there are genuine planets far out in the Kuiper belt is still debated, but recent research suggests the possibility that planets can still form despite great distances from the center of a solar system. Calculations suggest that the two planets are located almost 200 astronomical units from the center of our solar system—one astronomical unit being the distance of the Earth to the sun, (93 million miles). One of these planets may be ten times the size of our planet.
The search for a ninth planet to replace Pluto continues, and with this search, Yuggoth’s location is pushed ever further out into the cold and dark of space. This location, far out in the Kuiper belt, beyond Neptune, where comets roam and icy worlds take centuries to orbit a faraway sun, is probably what H.P. Lovecraft had in mind with his famous couplet: “I have seen the dark universe yawning/Where the black planets roll without aim—/Where they roll in their horror unheeded/Without knowledge or lustre or name.”