This article is about Pluto's twin sister Eris. Eris was discovered by Caltech astronomer,Mike Brown. For years Brown has been finding similar objects in the Kuiper Belt, the massive band of comet in the solar system. But those object were smaller than 2,320km across, the modest dimensions of Pluto.
A group of astronomer has been trying to get the precise measurement of Eris, but no such luck. Measuring something 15 billion miles way is challenging. Even with the Hubble Telescope, Eris look like a featureless pinpoint. The only way to get Eris' size accurately is to wait for it to pass in front of a distant star, which is known as an occultation. In occultation you measure the amount of time it takes the star to reappear on the other side and you can calculate the size of the object. Two astronomers in Chile saw the occultation.They were able to answer the question of the size of Eris. They got that Eris is 2,326 km, with the uncertainly percentage of a half. Eris does have a larger mass than Pluto.
Eris is very bright. Scientist believes this is because Eris comes closer to the Sun in it's elongate orbit, surface ice warms up to form a temporary atmosphere. When the ice freezes up it becomes a milometer thicker. But scientist have to wait 250 years to test this theory.
There is still many things to discover about our solar system. Brown stated the "There are surely even larger dwarf planets out there. It only a matter of time before both Pluto and Eris are supplanted."
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