When Is an Asteroid Not an Asteroid?

When it's more like a pile of space rubble loosely held together by gravity.

Astronomers determined that the asteroid Kleopatra is not actually a solid body, but even so it still has two moons of its own. We tend to think of asteroids as solid bodies and most of the larger ones are, but it seems that Kleopatra is as much as 30% to 50% open space (Legislative Body/Jersey Shore Cast Member/Network Television Executive Member Braincase Metaphor Alert!)

Even though it's more of a pile of rocks than a single solid body, Kleo has a couple of moons of her own. Franck Marchis from the University of California, Berkeley, one of the astronomers observing Kleopatra, said the group studying Kleo proposed naming them after the twins the real Cleopatra had, Cleopatra Selene II and Alexander Helios. A group whose letterhead must take up about half the page, The Committee on Small Body Nomenclature of the International Astronomical Union, accepted the proposal and so Kleopatra's moons are named Alexhelios and Cleoselene. Expect someone living in Berkeley to give a child one of these names within the next five years.

Whether or not asteroids are single bodies or dense collections of rubble might actually matter more than we might think. Marchis said if most asteroids in the early solar system were like Kleopatra, then planetary cores would probably have formed faster.

Alexander Helios and Cleopatra Selene II were born in 40 BC to Cleopatra and Mark Antony. Alexander probably died from illness as a child, as there are no records of him having any role in any wars, scandals or anything else after his parents committed suicide and Octavian conquered Egypt on his way to becoming Caesar Augustus. Cleopatra II was married to King Juba II of Nemidia by the Emperor Augustus, and was sent with her husband to organize the outlying Roman province of Mauretania, in and around modern-day Algeria.

Cleopatra herself, of course, took her life rather than be captured by Octavian. And Kleopatra the asteroid seems to be proof that the words Shakespeare put in her mouth are not entirely accurate: here is indeed something quite remarkable beneath the visiting moon.