At first the astronomers thought it was a mistake. They had found a carbon-covered asteroid floating among countless icy bodies far away in our solar system. The newly discovered space rock, which they named 2004 EW95, was something the scientists would have expected to have seen in the asteroid belt between Mars and Jupiter. Instead, it was dancing near Neptune.

Their finding, which was published Wednesday, suggests that 2004 EW95 is the first of a new class of space objects lurking in the outer solar system, in a vast, frigid region known as the Kuiper belt that still contains many mysteries. The researchers believe that the asteroid sling-shotted from the inner solar system some 4.5 billion years ago, and that it may provide insight into the early formation of our planets.

Using the European Southern Observatory’s Very Large Telescope, Tom Seccull, a doctoral student at Queen’s University Belfast in Northern Ireland, and his colleagues examined light signatures from the icy surfaces of Kuiper belt objects. They noticed something strange about one object that measured nearly 190 miles long and was located 2.5 billion miles from Earth. Their analysis showed that this object did not share the same frigid past as the ice balls drifting nearby.

“When we first looked at this, we thought it was wrong,” said Mr. Seccull, who is lead author of the paper published in The Astrophysical Journal Letters. “The rock had been altered by the presence of liquid water.”