618 Encyclopedia of the Solar System
TABLE 4 Binary KBOs^1Name Number Prov Des a^2 e^3 Period^4 Mass^5Resonant
Pluto/Charon 134340 19,636 0.0076 6.38722 14,710
47171 1999 TC 36 7,640 50.4 13.9
26308 1998 SM 165 11,310 130 6.78
Classical
2005 EO 304
2003 UN 284
2003 QY 90
2001 QW 322
2000 CQ 114
2000 CF 105
1999 OJ 4
1998 WW 31 22,300 0.82 574 2.7
134860 2000 OJ 67
88611 2001 QT 297 27,300 0.240 825 2.3
80806 2000 CM 105
79360 1997 CS 29
66652 1999 RZ 253 4,660 0.46 46.263 3.7
58534 1997 CQ 29 8,010 0.45 312 0.42
Scattered
2001 QC 298 3,690 19.2 10.8
Eris 136199 2003 UB 313
136108 2003 EL 61 49,500 0.05 49.12 4,200
82075 2000 YW 134
48639 1995 TL 8(^1) Courtesy Keith Noll.
(^2) Semimajor axis in km.
(^3) Eccentricity.
(^4) Period in days.
(^5) Mass in units of 10 (^18) kg.
FIGURE 14 Binary KBO. The apparent orbit of the fainter
component of 1998 WW 31 relative to the brighter component on
the plane of the sky. (Courtesy of Christian Veillet, Keith Noll,
and NASA)
are the wide separation and similar diameter of each pair of
components. These unusual features make it unlikely that
collisions between two KBOs created each binary system,
as in the case of the Earth and the Moon. Similarly, it isn’t
likely that one KBO gravitationally captured another KBO
to form a binary system. A mechanism put forth by Stuart
Weidenschilling suggests that it is possible to create a loosely
bound KBO binary by collision and capture in the pres-
ence of a third body. His mechanism requires many more
KBOs than are seen today; perhaps such a mechanism oper-
ated long ago in a more densely populated Kuiper Belt (see
the next section). Peter Goldreich put forth a mechanism
wherein capture takes place during a close encounter as a
result of the dynamical friction with the many surrounding
small bodies. Each of these mechanisms produces its sig-
nature on the population of binaries we see today. For ex-
ample, Weidenschilling’s mechanism favors the production