  We have searched the four brightest objects in the Kuiper belt for the
presence of satellites using the newly commissioned Keck Observatory Laser
Guide Star Adaptive Optics system. Satellites are seen around three of the four
objects: Pluto (whose satellite Charon is well-known), 2003 EL61, and 2003
UB313. The object 2005 FY9, the brightest Kuiper belt object after Pluto, does
not have a satellite detectable within 0.4 arcseconds with a brightness of more
than 0.5% of the primary. The presence of satellites to 3 of the 4 brightest
Kuiper belt objects is inconsistent with the fraction of satellites in the
Kuiper belt at large at the 99.1% confidence level, suggesting a different
formation mechanism for these largest KBO satellites. The satellites of 2003
EL61 and 2003 UB313, with fractional brightnesses of 5% and 2% of their
primaries, respectively, are significantly fainter relative to their primaries
than other known Kuiper belt object satellites, again pointing to possible
differences in their origin.
