Artist's impression A Field/NASA

The composition of 2003 EL61 is mainly rock, with an icy coating. This coating makes the object very bright, approaching that of pure snow.

Two much smaller companions orbit 2003 EL61. One has an estimated diameter of 310 km, the other an estimated diameter of 170 km.

2003 EL61 follows an elliptical orbit with an inclination of 23.19 degrees to the solar plane. It is an average distance from the Sun of about 43.34 Astronomical Units or AUs (where an AU is the distance between the Earth and the Sun). It is currently approximately 51 AUs from the Sun. It takes 285 Earth years to complete an orbit.

Several asteroids have similar orbits to 2003 EL61. They have similar composition and surface characteristics as well. This, along with unusual shape and rotation of 2003 EL61 suggest they are the result of a break up following a collision. Estimates of the size of 2003 EL61 prior to the collision give it a diameter of 1660 km. During the collision, it lost approximately 20 percent of its mass, mostly ice.

There has been considerable controversy accompanying the discovery of the dwarf planet. A group of astronomers led by Jose Luis Ortiz Moreno, at the Sierra Nevada Observatory in Spain, announced the discovery of the object on July 25, 2005, this was published on the 27 by the Minor Planet Centre (MPC).

A rival group led by Michael E. Brown at Caltech, had been observing the object for half a year with the 1.3 m SMARTS Telescope, but had not made any public announcement. They had however mistakenly made their observational data available on the internet.

The Caltech group originally supported the Spanish groups claim. But when they discovered that someone from the Spanish group had accessed the SMARTS Telescope observation logs prior to the MPC announcement, they accused Ortiz's group of a serious breach of scientific ethics and asked the MPC to remove the credit for the discovery from them.

Ortiz admits he accessed the internet telescope a day before making his announcement, but claims they did not use the data. He says they were just checking whether it could be the same object they had already found.

The MPC still give credit for the discovery of (136108) 2003 EL61 to the Ortiz group.

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