Another Planet
Written by Jerry Coffey
Percival Lowell observing Mars.
When Clyde Tombaugh discovered another planet, Pluto, in 1930, these theories seemed to have been proven correct. However, in 1978, it was proven that Pluto was too small to account for the perturbations seen in the orbits of the two giants planets. This launched an immediate search for a possible tenth planet. The search was abandoned by a large number of astronomers in the early 1990s, because of a study of measurements made by the Voyager 2 spacecraft found that the irregularities observed in Uranus's orbit could be due to a slight overestimation of Neptune's mass.
Today, the astronomical community widely agrees that another planet, often referred to as Planet X, does not exist. Recently the concept of Planet X has been revived by a number of astronomers to explain other anomalies observed in the outer Solar System. In popular culture, and even among some astronomers, Planet X has become a stand-in term for any undiscovered planet in the outer Solar System, regardless of its relationship to Lowell's original hypothesis. Other trans-Neptunian planets have also been suggested, based on different evidence.
In the early 1800's there were only seven known planets. In the 1840s, a French mathematician named Urbain Verrier applied Newtonian mechanics to analyze perturbations in the orbit of Uranus, and hypothesized that they were caused by the gravitational pull of another planet yet to be discovered. He predicted the position of this new planet and sent his calculations to German astronomer Johann Galle. On 23 September 1846, the night following his receipt of the letter, Galle and his student discovered Neptune, exactly where Verrier had predicted it should be. Very shortly after that, there were innumerable theories and calculations made to show the existence and location of another planet beyond Neptune. Science just had not caught up to the theories enough to allow them to be proven.
Current theories about another planet surround the existence of the Kuiper cliff, which is a point where the Kuiper belt suddenly ends at a distance of 48 astronomical units from the Sun. There is some speculation that this sudden drop-off may be attributed to the presence of an object with a mass between that of Mars and Earth located beyond 48 AU. The possibility of a Mars-like planetoid in a circular orbit at 60 AU has been doubted because, theoretically, such an object would be so bright that it would have been discovered by now. Astronomers have not excluded the possibility of a more massive Earth-like planetoid located further than 100 AU with an eccentric and inclined orbit. Computer simulations have suggested that a body roughly the size of Earth, ejected outward by Neptune early in the Solar System's formation and currently in an elongated orbit between 80 and 170 AU from the Sun, could explain not only the Kuiper cliff but also the peculiar detached objects like Sedna.
The search for another planet(Planet X?) has been going on since man discovered the first planet besides Earth. Ever expanding and improving science will some day prove there are more planets out there. Patience is all that is needed. Here is a good article about planets beyond Neptune. Here on Universe Today we have a great article about Planet X. Astronomy Cast offers a good episode about the multitude of planets that are orbiting other stars.
Filed under: Astronomy
Tags: another planet, planet x
