First-ever quadruple asteroid system discovered

A researcher from Thailand’s National Astronomical Research Institute (NARIT) has discovered the third moon orbiting asteroid 130 Elektra, which is in the asteroid belt. This is a great first, making this object the first known quadruple asteroid system.

Reveal the weakest objects in the Solar System

SPHERE is a set of instruments installed on the Very Large Telescope (VLT), in northern Chile. It makes it possible to search for exoplanets from the earth’s surface by circumventing the problems of the turbulent atmosphere of the Earth. The light collected through the main mirror passes through an adaptive optics (AO) system which constantly monitors the fluctuation of light from the observed object due to atmospheric distortion. Then, thousands of actuators perform real-time correction to compensate for the distortion more than a thousand times per second.

This process results in a much sharper image than would otherwise be possible. In recent work, researchers have used this technique and new algorithms to detect new satellites orbiting known asteroids in the Very Large Telescope (VLT) archive. Concretely, these algorithms made it possible to reduce the glare of the light of the main asteroids in order to reveal fainter objects evolving around them .

Most asteroids are solitary, but some evolve in pairs. In this configuration, a small object generally orbits around a larger one. On rare occasions, triple asteroid systems have been discovered, with two moons orbiting a larger body. More recently, the SPHERE instrument allowed the detection of a first quadruple system . Details of the study are published in Astronomy & Astrophysics .

Elektra and her three companions

The asteroid 130 Elektra evolves in the outer region of the main asteroid belt, between Mars and Jupiter, and was discovered in 1873. Its diameter is about 200 km.

Its first moon was not spotted until much later, in 2003. This roughly six-kilometer-wide rock completes one revolution of Elektra every five Earth days at a distance of about 1,300 km. A second moon was then spotted in 2014. It is a rock just two kilometers wide orbiting 500 km from Elektra. She goes around it in 1.2 days.

Now we know that a third moon is also present. It is only 1.6 km wide, orbiting the main body every sixteen hours at a distance of 344 km . While the first two moons move in roughly circular paths, this new satellite follows an eccentric egg-shaped orbit.

It may be the first quadruple asteroid discovered, but 130 Elektra probably won’t be the last . This method could indeed be used to image other asteroids and planets in the Solar System, potentially revealing other hidden objects.

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