The Canada-France-Hawaii Telescope and the Hubble Space Telescope track a binary object at the fringe of Solar System

Paris, April 18, 2002

An international team led by Christian Veillet, an astronomer at the Canada-France-Hawaii Telescope (CFHT) (National Research Council of Canada – Centre National de la Recherche Scientifique of France – and University of Hawaii), bring us the highest-precision observations ever made of a binary object of the Kuiper Belt, "1998 WW31". The discovery of this binary system at the CFHT was announced a year ago by Christian Veillet and his team. Their work is published in Nature, April 18, 2002.

The use of very precise measurements obtained with Hubble between July 2001 and February 2002, combined with measurements taken from the ground, obtained mainly at the CFHT, has made it possible to compute the orbital parameters of the binary system. With an orbital period of 570 days and an eccentricity(1) of over 0.8, the pair formed by 1998 WW31 is very different from the pair made up of the planet Pluto and its satellite Charon, the only double system known hitherto in the Kuiper Belt(2) . The distance between the two components of 1998 WW31 varies in the range 4,000 km to 40,000 km and the mass of the system can be estimated to be 1/5000th of the mass of Pluto/Charon.

The announcement of the binary nature of 1998 WW31 was followed by the discovery, by other teams, of six other binary systems in this region of the Solar System, and the region is thought to be a source of new short-period comets. More than one percent of the half a thousand or so objects of the Kuiper Belt that are known today are binary systems: a surprising fact that many people are going to try and explain in what is proving to be a highly promising research field.


(1) Eccentricity: quantity that measures the elongation of the ellipse representing the orbit; the eccentricity of a spherical orbit is equal to 0.
(2) Kuiper Belt: reservoir of small objects beyond Neptune’s orbit.

Researcher contact:
Christian Veillet
Tel: (808) 885-3161 (Hawaii)
e-mail: veillet@cfht.hawaii.edu

Press contact:
Martine Hasler
Tel : +33 1 44 96 46 35
e-mail : martine.hasler@cnrs-dir.fr