Poor Pluto faces another assault on its status. First scientists wrestled over its classification as a planet. Now an astronomer says it's not the only distant object in our solar system to orbit with a companion.

Christian Veillet of the University of Hawaii says he and his colleagues have spotted a double object, called 1998 WW_31, circling the Sun beyond the orbit of Neptune. Pluto's moon Charon was discovered in 1978.

"Pluto is not unique!" Veillet wrote Monday in an e-mail to SPACE.com.

The new objects were spotted moving together in December with the 142-inch (3.6-meter) Canada-France-Hawaii Telescope. Previous images of the objects also showed them moving in tandem. There are no reliable estimates of the objects' sizes, but they are likely a tenth the size of tiny Pluto, which measures 1,430 miles (2,301 kilometers) across, Veillet said.

The maximum distance between the two new objects is at least 24,800 miles (40,000 kilometers).

Some astronomers now refer to Pluto, 1998 WW_31 and all objects orbiting beyond Neptune as Trans-Neptunian Objects, or TNOs. About 300 such objects have been identified. Pluto orbits at an average of 38 AU (astronomical units) from the Sun. (An astronomical unit is the distance from the Earth to the Sun -- 93 million miles, or 149.7 million kilometers.)