Planets are not the only astronomical objects that can have their own naturally occurring satellites. It turns out that asteroids can have satellites and often act as satellites to larger planets themselves. A team of astronomers has recently discovered a record-breaking asteroid with three companions, all of them smaller, more compact asteroids. This four-member system is bound by such complex gravitational interactions that the traditional three-body problem looks simplistic by comparison.
The asteroid in question is known as (130) Elektra. It was first discovered by astronomer Christian Peters in 1873. The asteroid has a size of 200 kilometres and a mass of 7 x 10^18 kilograms, which is enough to generate gravitational forces capable of capturing and holding three smaller asteroids - S/2003 (130) 1, S/2014 (130) 1 and S/2014 (130) 2.
The year in the name of the satellite asteroids reflects the year the satellite was identified. The second and third satellites were discovered thanks to data collected in 2014 by the SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument on the Very Large Telescope (VLT).
So why was it so difficult to find and identify all the satellites of the asteroid (130) Elektra? The main problem is the presence of optical distortions and diffraction effects. Optical signals from satellites are hidden in a "halo" of distortion from the main object most of the time. But scientists have managed to develop special algorithms PIC (Projection, Interpolation, Convolution) and PSF (Point Spread Function), which cleared the image from distortion and allowed "manifest" images of asteroid satellites, sacrificing the resolution and quality.
Nevertheless, the resulting images clearly show the position of the satellite asteroids, even though there are still traces of a "halo" around the main object. Such processing has made it possible to identify the smallest and closest satellite S/2014 (130) 2 and to calculate its orbit, which lies 344 kilometres above the surface of asteroid (130) Elektra.
In the future, the application of such sophisticated image processing can be used in relation to images of other asteroids. Scientists suspect that there are many more such "self-organised" systems in the asteroid belt, and the complexity and mechanics of some of them will exceed even the current four-body problem.