For the first time since Eris was designated a planet in 2005, astronomers have been granted the clearest image of the planet possible. The discovery of Eris let to Pluto losing its status as a planet. Eris is also roughly three times farther away from the sun than Pluto, making one year on Eris last 557 Earth years. Eris passed in front of a star last year, giving astronomers the chance to measure the size more accurately. New measurement estimates published by the journal Nature this month have revealed that Eris is probably the same size as Pluto, and also one of the brightest objects in the solar system. Prior to this, Eris' image was fuzzy at best due to the immense distance from the earth. “It's very difficult, because it's so small in the sky,” said lead author Bruno Sicardy, a planetary scientist at Pierre and Marie Curie University and Observatory in Paris. When an object such as Eris crosses over a star it blocks off a certain amount of light. The amount of light blocked allows scientists to calculate the object's size. This event is known as stellar occultation. To witness the occultation that led to this find last year required being at a precise location at a precise time. Sicardy's team asked 26 different telescope operators around the world to make observations. Of the 26, only three telescopes, all in Chile, managed to see the occultation. The data that was gathered indicated that Eris' diameter is roughly 1,445 miles. Pluto is believed to be somewhere between 1,429 and 1491 miles across. The surface area of the dwarf planet, compared to the amount of light reflected off the surface, is brighter than ever anticipated. This discovery has made Eris one of the brightest objects in the solar system, even though the surface of the planet shuld have been darkened from cosmic ray and micrometeorite bombardment. The ‘shininess' is believed to be caused by a millimetre-thick layer of methane and nitrogen frost, cating the planet's surface. The frost is believed to be the remnants of what was once the atmosphere of Eris as it travelled further and further away from the sun. Estimates also point to Eris being roughly 27 percent heavier than Pluto, which has led scientists to conclude the planet must contain relatively more rock and less ice, Caltech astronomer and member of the team that found Eris, Mike Brown said. “We really think [Eris and Pluto] should have been made at the same time out of the same materials — so really, it's bizarre that they're so different,” Brown said. BM
