Shaped like a squashed football, the ice-covered body 2003 EL61 rotates faster and reflects more sunlight than any other object in the outer solar system, is about as big as Pluto, and even has two moons. Now, astronomers have discovered that this fringe object, located beyond Neptune in a region called the Kuiper belt, has another distinction. It's the first Kuiper belt denizen known to have an extended family.
Five smaller members of the belt, although not close to 2003 EL61, have nearly identical surface properties and orbits, Mike Brown of the California Institute of Technology in Pasadena and his colleagues report in the March 15 Nature. The researchers suggest that the family arose soon after the birth of the solar system, when a Pluto-size body smashed into 2003 EL61, creating the fragments that Brown's team has found.
The researchers, who discovered 2003 EL61, had already proposed that a giant impactor had pummeled the body. Such a collision could accou