Strange ‘dog bone’ asteroid is bigger than New Jersey and has two moons

Scientists took a close look at one of the most distinctive giant asteroids and found it even stranger than previously thought. Cleopatra is around 270 kilometers long and shaped like a dog bone or a dumbbell, and is home to two moons, named AlexHelios and CleoSelene, in honor of the children of the Egyptian Queen.

“Kleopatra is truly a unique body in our solar system,” SETI institute astronomer Franck Marchis said in a statement. “Science is making a lot of progress through the study of weird outliers. I think Cleopatra is one of them and understanding this complex and multiple asteroid system can help us learn more about our solar system.”

Marchis has led new research into Cleopatra’s strange shape and composition, which is published Thursday in the journal Astronomy and Astrophysics.

A team of astronomers used the very large telescope at the European Southern Observatory in Chile to get a better picture of Cleopatra’s unusual shape. They discovered that one of the space rock’s lobes was larger than the other and determined its length, which is longer than the state of New Jersey, about half the length of the English Channel.

A second study published in the same journal refined the previously estimated orbits of the two moons around Cleopatra, allowing researchers to calculate the mass of the main asteroid, which turned out to be a surprise.

Cleopatra has a mass a third less than that indicated by previous estimates, a strange development given that she is believed to be metallic. All of this suggests that it is more of a pile of porous pebbles than a large lump of iron.

Asteroids in rubble piles are not that rare. There are reasons to believe that Bennu, the asteroid recently visited and sampled by NASA’s Osiris-Rex spaceship, has a similar structure. Such space rocks can form when material from a major impact builds up or “builds up”, creating a new body. Researchers suspect that Cleopatra’s moons may also have been formed by similar processes.

Next, Marchis says he hopes to point more powerful telescopes at Cleopatra to see if it could accommodate more moons or other surprises.

“Kleopatra is a confusing multiple system,” the team’s document concludes. “This system certainly deserves special attention in the future, with extremely large telescopes and possibly a dedicated space mission, to decipher the entire history of its formation.”