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2021-2022: LXXX

"In nature nothing is perfect and everything is perfect. Trees can be contorted, bent in weird ways, and they're still beautiful." -Alice Walker

THE DAILY ASTRONOMER Wednesday, February 9, 2022

Quadruple Asteroid

Today's excursion into the wild and unbounded black yonder takes us into the asteroid belt, where one would find thousands upon thousands of these oddly shaped rocky bodies careening through the gulfs of interplanetary space. Our destination however is one asteroid, or, more correctly, a system of four asteroids: the first quadruple asteroid system to be discovered.

Vacillating between 3.7 and 2.4 AU* from the Sun, 130 Elektra is a carbonaceous asteroid approximately 200 kilometers in diameter. Discovered in 1873 -hence the comparatively low designation number- by German-American astronomer Christian Heinrich Friedruch Peters (1813-1890), Elektra has been known to possess two moons. The first moon was discovered in 2003; the second in 2014. Now, an astronomical team led by the National Astronomical Research Institute of Thailand's Anthony Berdeu has examined images of Elektra captured by the Very Large Telescope in Chile. They've recently announced the discovery of a small third moon moving within the orbits of the two previously discovered moons. This new moon measures merely 1 mile in diameter, smaller than its two companion moons (1.2 and 3.7 mile diameters).   As its mean distance from Elektra is only 220 miles, this meager little moon completes an orbit around its parent body every 16 hours!   

Images of Electra and two of its three "moons" captured by the European Southern Observatory's Very Large Telescope.

Observations show that the compositions of the moons and Elektra are similar, suggesting that the satellites are fragments of Elektra dislodged by a collision that occurred at an indeterminate time.      In fact, the small moon just discovered is so close to the main asteroid that it might eventually fall back onto it.

For now, astronomers are excited at the discovery of the first known quadruple asteroid system.   They are hopeful that the new algorithms that enabled the VLT astronomers to find Elektra's third moon will help them to find other such quadruples -and perhaps even quintuples- in the near future.

*AU = astronomical unit, equal to Earth's mean distance from the Sun or approximately 93 million miles.

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