December 2001- 1998 WW31
Distance from the Sun: The binary object has a semi-major axis of ~ 45 astronomical units (6.7 x 109 km or 4.2 x 109 miles). Distance from Earth: During the time of the HST observations (July 2001- February 2002) the binary system was ~ 46.5 astronomical units from the Earth. Distance between objects: The semi-major axis of the components of the binary system is ~ 22,300 km (13,900 miles). The eccentricity of the orbit makes this physical distance vary between 4,000 and 40,000 km (2,500 and 25,000 miles). Orbit: The binary objects have an orbital period about each other of ~ 570 days. The system orbits the Sun every 300 years.
The HST image is roughly 7 arcseconds (roughly 226,000 km or 141,000 miles) across. The binary objects are estimated to be roughly 150 km and 130 km in diameter. Total Mass: The binary objects have a total mass of 0.00021 that of Pluto.
Principal Astronomers: C. Veillet (CFHT), J. W. Parker (SwRI), I. P. Griffin (STScI), B. G. Marsden (SAO), A. Doressoundiram, (Observatoire de Paris), D. J. Tholen (Univ. of Hawaii), M.W. Buie (Lowell Obs.), M. J. Holman (SAO)
Summary of All Data
KPNO 4-m telescope: November 1998; January and November 1999; November 2000
CFH 3.6-m telescope: January and December 2000; J
HST WFPC2: July 2001- February 2002
F555W (V), F675W (R), F814W (I)