Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Binary asteroid
open-in-new
<p>A binary asteroid is a system of two <a href="/facts/Asteroid/g7Ulr1VB">asteroids</a> orbiting their common <a href="/facts/Barycenter/Fw9renao">barycenter</a>. The binary nature of <a href="/facts/243_Ida/gqgaPb12">243 Ida</a> was discovered when the <a href="/facts/Galileo_(spacecraft)/H57agAgz">Galileo spacecraft</a> flew by the asteroid in 1993. Since then <a href="/facts/List_of_minor-planet_moons/hIzB5S7X">numerous binary asteroids</a> and <a href="/facts/Minor-planet_moon/hIzB5S7X">several triple asteroids</a> have been detected. </p><p>The mass ratio of the two components – called the "primary" and "secondary" of a binary system – is an important characteristic. Most binary asteroids have a large mass ratio, i.e. a relatively small satellite in orbit around the main component. Systems with one or more small <a href="/facts/Minor-planet_moon/hIzB5S7X">moons</a> – also called "companions" or simply "satellites" – include <a href="/facts/87_Sylvia/mmMe8cMc">87 Sylvia</a>, <a href="/facts/107_Camilla/dfjobzUq">107 Camilla</a> and <a href="/facts/45_Eugenia/ABApN2JR">45 Eugenia</a> (all triples), <a href="/facts/121_Hermione/lgmPWUw2">121 Hermione</a>, <a href="/facts/130_Elektra/CDXkSMKX">130 Elektra</a> (a quadruple), <a href="/facts/22_Kalliope/6smM5NHG">22 Kalliope</a>, <a href="/facts/283_Emma/0I5h4Un6">283 Emma</a>, <a href="/facts/379_Huenna/VAuBs5Ty">379 Huenna</a>, <a href="/facts/243_Ida/gqgaPb12">243 Ida</a> and <a href="/facts/4337_Arecibo/R8aXWvkK">4337 Arecibo</a> (in order of decreasing primary size). Some binary systems have a mass ratio near unity, i.e., two components of similar mass. They include <a href="/facts/90_Antiope/jaVENDmY">90 Antiope</a>, <a href="/facts/(300163)_2006_VW139/h2DCmQ15">2006 VW139</a>, <a href="/facts/2017_YE5/G8zQLuKC">2017 YE5</a> and <a href="/facts/69230_Hermes/56BB51Ms">69230 Hermes</a>, with average component diameters of 86, 1.8, 0.9 and 0.8 km, respectively. </p><p>In August 2024 <a href="/facts/Gaia_(spacecraft)/dlvcdkoN">Gaia</a> reported 352 new binary asteroid candidates. </p>