of 26 identified members, with a lifetime of more than 530 million (or even 1 billion) years, can be further divided into two clusters in the pseudo-proper element space: 3789 Zhongguo 11266 Macke 11573 Helmholtz 14871 Pyramus 22740 Rayleigh 31249 Renéefleming 45511 Anneblack Strongly unstable group Related but distinct from the "long-lived" Griquas and Zhongguos, is the group of "unstable" Hecuba-gap asteroids: 1921 Pala 1922 Zulu 5201 Ferraz-Mello 5370 Taranis () 8373 Stephengould 9767 Midsomer Norton () 65541 Kasbek In 2005, further research expanded this group of 16 bodies with an additional 31 multi-opposition asteroids, that show life-times of less than 70 million years. It is also thought that approximately 25% of the short-lived population are "extremely unstable" with lifetimes of less than 2 million years. () () () Among the unstable population, some asteroids have such a high eccentricity with a perihelion of less than 1.3 AU, that qualifies them as a near-Earth object. These five bodies (with their current eccentricity taken from the JPL SBDB in parenthesis) are 5370 Taranis (0.64), (0.65), (0.70), (0.66), (0.72). References External links On the Origin of the Long-Lived Asteroids in the 2:1 Mean-Motion Resonance with Jupiter, 8-slide presentation, Chrenko, 2014 Dynamics of the Solar System – Publication overview, Miroslav Broz, Institute of Astronomy, Charles University EasySky, orbital diagram Minor planet groups/families, www.projectpluto.com