Detection of two binary trans-Neptunian objects, 1997 CQ29 and 2000 CF105, with the Hubble Space Telescope

Images of the trans-Neptunian objects 1997 CQ(29) and 2000 CF105 obtained with the Hubble Space Telescope WFPC2 camera show them to be binary. The two components of 1997 CQ29 were separated in our images by 0."20 +/- 0."03 in 2001 November and by 0."33 +/- 0."01 in 2002 June/July. The corresponding minimum physical distances are 6100 and 10,200 km. The companion to 2000 CF105 was 0."78 +/- 0."03 from the primary, at least 23,400 km. Six other objects in the trans-Neptunian region, including Pluto and its moon Charon, are known to be binaries; 1997 CQ29 and 2000 CF105 are the seventh and eighth known pair. Binarity appears to be a not uncommon characteristic in this region of the solar system, with detectable companions present in 4% +/- 2% of the objects we have examined.