A team of astronomers have obtained the sharpest and most detailed images yet of the asteroid Kleopatra, using the European Southern Observatory's Very Large Telescope (ESO's VLT).
The observations have allowed the team to constrain the 3D shape and mass of this peculiar asteroid, which resembles a dog bone, to a higher accuracy than ever before. Their research also provides clues as to how this asteroid and the two moons that orbit it formed.
"Kleopatra is truly a unique body in our Solar System," said lead researcher Franck Marchis, an astronomer at the SETI Institute in Mountain View, US, as per the study was published in the journal Astronomy and Astrophysics.
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"Science makes a lot of progress thanks to the study of weird outliers. I think Kleopatra is one of those and understanding this complex, multiple asteroid system can help us learn more about our Solar System," Marchis added.
Kleopatra orbits the Sun in the Asteroid Belt between Mars and Jupiter. Astronomers have called it a "dog-bone asteroid" ever since radar observations around 20 years ago revealed it has two lobes connected by a thick "neck".
In 2008, Kleopatra was found orbited by two moons, named AlexHelios and CleoSelene, after the Egyptian queen's children.
To find out more, the team used snapshots of the asteroid taken at different times between 2017 and 2019 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO's VLT.
As the asteroid was rotating, they were able to view it from different angles and to create the most accurate 3D models of its shape to date.
They constrained the asteroid's dog-bone shape and its volume, finding one of the lobes to be larger than the other, and determined the length of the asteroid to be about 270 kilometres or about half the length of the English Channel.
Kleopatra's rubble-pile structure and the way it rotates also give indications as to how its two moons could have formed. The asteroid rotates almost at a critical speed, the speed above which it would start to fall apart, and even small impacts may lift pebbles off its surface, the astronomers explained.
The team believe that those pebbles could subsequently have formed AlexHelios and CleoSelene, meaning that Kleopatra has truly birthed its own moons.