There are five recognized dwarf planets in our solar system, and Pluto is probably the most well-known and well-loved. It has been debated that there are an unknown number of dwarf planets located far beyond Pluto, and science might be on the brink of meeting two of them. The research was published in two papers in the Monthly Notices of the Royal Astronomical Society. Carlos de la Fuente Marcos from Complutense University of Madrid in Spain was lead author of both papers.
The two dwarf planets were suggested in order to explain the orbits of extreme trans-Neptunian objects (ETNO), which are minor planets beyond Neptune. Theory suggests that these objects should have a semi-major axis of around 145 AU, with an orbit very close to the plane of other planets in the solar system. However, study of 12 ETNOs revealed that the inclination of their orbits was closer to 20 degrees, with semi-major axes vastly varying, reaching up to 525 AU.
These discrepancies could be explained by the gravitational forces of the suggested dwarf planets through what is known as the Kozai mechanism. The researchers compared what they were seeing in the orbits of the ETNOs with Jupiter's influence over Comet 96P/Machholz1.
"This excess of objects with unexpected orbital parameters makes us believe that some invisible forces are altering the distribution of the orbital elements of the ETNO and we consider that the most probable explanation is that other unknown planets exist beyond Neptune and Pluto," Carlos de la Fuente Marcos explained in a press release. "The exact number is uncertain, given that the data that we have is limited, but our calculations suggest that there are at least two planets, and probably more, within the confines of our solar system."
The observations by the team were very far outside of what theory says about planetary formation in our solar system, though they were able to find support for their ideas in other planetary systems. Data collected using the Atacama Large Millimeter Array, a series of radio telescopes in Chile, was used to analyze the planetary disc around the star HL Tauri, about 450 light-years from Earth. The star is less than 100,000 years old yet more massive than our sun. The disc exists about 100 AU away from the star, indicating that planets can form further away from a star than previously believed.
Of course, the researchers only used a small sample of the ETNOs out there, so the numbers might not be an accurate representation. Further study is needed to confirm orbital anomalies that could only be explained by the presence of a dwarf planet. Additionally, astronomers would still need to find the actual dwarf planets in question. Though it has been supposed that there could be hundreds more out there, confirming at least these two would have tremendous implications for current theories of planetary formation.
"If it is confirmed, our results may be truly revolutionary for astronomy," concluded de la Fuente Marcos.
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