Binary minor planets are a relatively recent discovery, although they had been hypothesized to exist since shortly after the discovery of Ceres, more than 200 years ago. It is not unusual that TNOs have binary companions, and more are being discovered all the time. "A binary planet" is a pair of worlds that are similar in mass. Each orbits the other around a gravitational balance point that is between the two - a location called the center of mass, or the barycenter. The pair may have born like twins, or may be produced by collisions, where a single body is split in two. The two objects usually have similar size, so it's not always clear which is the TNO and which is the satellite. There are even contact binaries - the objects are literally touching each other! The first transneptunian binary (TNB) was identified in 1978 with the discovery of Charon. However, since at that time the existence of the Kuiper Belt had yet to be established, Pluto was considered a major planet. The first discovery of a binary KBO (1998 WW31) was announced on April 16, 2001. Within a year after this discovery six other KBOs were discovered to be binaries. "It's amazing that something that seems so hard to do and takes many years to accomplish can then trigger an avalanche of discoveries," said Veillet, the discoverer of the satellite. Photo: Copyright © Susanna Kauppinen.
Altjira and S/2007 (148780) 1
Borasisi and Pabu Ceto and Phorcys Logos and Zoe Orcus and Vanth Pluto and Kharon Teharonhiawako and Sawiskera Typhon and Echidna 1995 TL8 1997 CS29 1998 SM165 and S/2001 (1998 SM165) 1 1998 WW31 and S/2000 (1998 WW31) 1 1999 OJ4 and S/2002 (1999 OJ4) 1 1999 RA216 1999 RT214 1999 TC36 and S/2001 (47171) 1 2000 CF105 and S/2002 (2000 CF105) 1 2000 CM105 and S/2002 (2000 CM105) 1 2000 CQ114 and S/2003 (2000 CQ114) 1 2000 OJ67 and S/2003 (2000 OJ67) 1 2000 OL67 2000 QL251 2000 WK183 2000 YW134 and S/2002 (2000 YW134) 1 2000 YW183 2001 CZ31 2001 FL185 2001 KP76 2001 QC298 2001 QG298 2001 QW322 and S/2001 (2001 QW322) 1 2001 XR254 2002 GZ31 2002 PD149 2002 UX25 2002 VA131 2002 VS130 2002 WC19 2003 QW111 2003 QY90 2003 TJ58 2003 UN284 2004 PB108 2004 SB60 2005 EO304 2006 SF369 Kuiper Belt Binaries by Kirsti Melto EKOs From the Distant Past New Horizons site NASA/HST news release David Jewitt's Kuiper Belt site SkyTonight.com article about contact binaries |