Eris – The Planet of Discord

On October 21, 2003, a photograph of the nocturnal sky was taken, where almost 2 years later, in January 2005, evidence was raised that there might be a 10th planet at the borders of our solar system: Eris, located in the Kuiper Belt and named after the Greek godess of discord. And discord it should be, because Eris as a planet is rather small and astronomers were arguing, whether it is a planet at all. The end of the story resulted in loosing another planet of the solar system. Pluto lost its status as a planet furthermore also be called only a ‘dwarf planet’.

That Eris was discovered was mainly due to good luck after all. Using the 1200 mm Samuel Oschin telescope in California, Eris’ image was taken in 2003 but due to the dwarf’s very slow motion around the Earth it was not detected yet. The team used an image search software and programmed it to exclude all objects moving slower than 1.5 arcseconds per hour in order to reduce the number of false positives. Only a re-analysis could reveal Eris’ existence in 2005.

Soon after its discovery, many research efforts have been accomplished in order to classify and specify the then unknown object. NASA initially described Eris as the tenth planet due to the fact that it may be larger than Pluto. However, the International Astronomical Union named a group of experts designated to find an exact definition for planets. As a result neither Eris nor Pluto could be classified as planets an from then on counted as ‘dwarf planets‘.

Eris depicts the most distant known natural object in our solar system. After many and long lasting discussions about its size, most scientists finally came to the conclusion that Eris has about the same size but is about 27% more massive than Pluto. Also its surface may be quite similar to Pluto’s, after observations with the Gemini North Telescope located in Hawaii, astronomers revealed the presence of methane ice and measured the presumably grey appearing dwarf’s temperature at about -243 to -217 degrees Celsius.

Another observation, also taking place in 2005 revealed that a moon is orbiting around Eris as well. It was called Dysnomia after the Greek goddess of lawlessness, who was also the daughter of Eris.

At yovisto you may enjoy the video lecture ‘Pluto, Eris, and the Dwarf Planets of the Outer Solar System‘ by Mike Brown, one of Eris’ discoverers.

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