Discovery of the first quadruple asteroid in the solar system

Astronomers have discovered the first known system of quadruple asteroids. A team from Thailand and France has spotted a third moon orbiting main-belt asteroid Elektra, moving the object into the record books.

Most asteroids are solitary travelers, but some are gravitationally bound in pairs – usually with a smaller object orbiting a larger one. On rare occasions, triple asteroid systems have been discovered, with two moons orbiting a larger primary body. It was as complex as asteroid systems, until now.

The asteroid Elektra, orbiting the Sun in the outer region of the Main Asteroid Belt, was first discovered in 1873, with a significant diameter of around 200 km (124 miles). However, its first moon was not spotted until 2003, when a 6 km (3.7 mile) rock was detected orbiting it every five days, at a distance of around 1,300 km (808 miles). Moon number two appeared in 2014 – a smaller rock just 2 km (1.2 miles) orbiting 500 km (310 miles) from Elektra every 1.2 days.

And now a third moon has been discovered, making Elektra a quadruple asteroid system. This is only 1.6 km (1 mile) wide, orbiting the main body every 16 hours at a distance of 344 km (214 miles). While the other two moons orbit in roughly circular paths, the third follows an eccentric egg-shaped orbit.

A diagram of the orbits of Elektra’s moons

NARIT/Anthony Berdeu

The discovery was made by Dr. Anthony Berdeu, applying new algorithms he developed to archival data from the Very Large Telescope (VLT) in Chile. These algorithms reduce the glare of light from the main asteroid and remove it from the image, allowing fainter objects to become visible. When this was applied to the 2014 dataset in which the second moon was discovered, Berdeu found the third. To confirm, the team applied the algorithms to two other Elektra datasets, and sure enough, the third moon was visible in each.

It may be the first quadruple asteroid discovered, but Elektra probably won’t be the last. The team says this method could be used to image other asteroids and solar system objects, to potentially find other hidden moons.

The research was published in the journal Astronomy and astrophysics.

Source: NARIT

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