Astronomers have discovered a new satellite orbiting the main belt asteroid (130) Elektra - the smallest object visible in this image. The team, led by Bin Yang (ESO, Santiago, Chile), imaged it using the extreme adaptive optics instrument, SPHERE, installed on the Unit Telescope 3 of ESO's Very Large Telescope at Cerro Paranal, Chile.

This new, second moonlet of (130) Elektra is about 2 kilometres across and has been provisionally named S/2014 (130) 1, making (130) Elektra a triple system. Exploiting the unprecedented sensitivity and spatial resolution of the instrument SPHERE, the team also observed another triple asteroid system in the main belt, (93) Minerva.

Asteroids are the relics of the building blocks that formed the terrestrial planets in the early days of the Solar System. Studying asteroids with multiple satellites is of crucial importance because their formation mechanisms can provide information about planet formation and evolution that cannot be revealed by other methods.

Using the data gathered with SPHERE the team inferred that both (130) Elektra and (93) Minerva were created in an erosive impact. As a result of the collision substantial chunks of matter can break away into space to form small satellites of one of the original bodies.

In this case the small separation of the satellites from their larger parent asteroids, the large mass ratios between the moonlets and the primaries and the same composition between moonlets and primaries support this theory.

Research paper by Yang et al.