Rubble pile asteroids likely form from debris coalescing after a giant impact, but the new analysis also suggests that AlexHelios and CleoSelene came from Kleopatra itself. That paradox suggests that Kleopatra has a " rubble pile" structure with lots of gaps in it, much like the asteroids Ryugu and Bennu that spacecraft have visited to study up close in recent years.Īn illustration comparing the size of asteroid Kleopatra with Italy.
The new value, plus sharpened models of the asteroid's size, suggests that the asteroid isn't as dense as scientists had believed, despite the fact that scientists think the object is metallic. With the new orbital data, scientists determined that Kleopatra is about 35% less massive than previous calculations estimated. "Because if the moons' orbits were wrong, everything was wrong, including the mass of Kleopatra." "This had to be resolved," Miroslav Brož, a solar system scientist at Charles University in the Czech Republic, said in the statement. That's a big deal, since scientists use the relationship between a body and its moons to understand the gravity at play and in turn the mass of the asteroid. In the process, the researchers determined that previous orbital models for those two small moons were incorrect. Because the images were so sharp, scientists could use them to finetune models of the main chunk of Kleopatra and to pinpoint how the two moons AlexHelios and CleoSelene orbit the larger body.
So the researchers used SPHERE to snap a series of images of Kleopatra.
(Image credit: ESO/Vernazza, Marchis et al./MISTRAL algorithm (ONERA/CNRS)) The result is super-sharp photographs, even inside the solar system.Įleven images of the asteroid Kleopatra captured between 20. That research requires spotting dim exoplanets around bright stars, so SPHERE is well-positioned to pick out the tiny moons orbiting the bright main body of Kleopatra 120 million miles (200 million kilometers) away from Earth.Īnd conveniently enough, the instrument is also equipped with a high-power adaptive optics system to adjust images for the blur that Earth's atmosphere otherwise causes. As the name suggests, the instrument was originally developed to spot alien planets, according to the European Southern Observatory (ESO), which operates the facility. Those new observations come from the Very Large Telescope's Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument. But even after the discovery, scientists wanted to keep an eye on the system - and observing the asteroid from 2017 to 2019 has finetuned researchers' picture of Kleopatra. In 2008, Marchis and his colleagues had spotted Kleopatra's two moons, AlexHelios and CleoSelene, named for two children of ancient Egypt's most famous queen.
“The texture of that asteroid seems very extreme to me,” said Cambioni.An image showing the asteroid Kleopatra and its two small moons, AlexHelios and CleoSelene, based on data gathered in July 2017. So, did Hollywood get it wrong after all? I would expect an asteroid of that size to be like asteroid Ceres (which is some 550 miles in size), he says. However, the surface of Ceres was imaged by the NASA Dawn mission, and it does not have sharp ice structures. The asteroid in Armageddon was about the size of Texas, says Cambioni.
The asteroid depicted in the film has a surface that’s extraordinarily treacherous full of sharp ice structures, more like the surface of an ever-mutable comet than a rocky body. The authors therefore infer that regolith blankets are uncommon on carbonaceous asteroids, which are the most numerous types of asteroid. In contrast, A 2005 Japanese mission to the asteroid Itokawa, an S-type asteroid with rocks of a different composition than Bennu and Ryugu, found it to have a smooth, less rocky surface. This finding has also been born out by Japan’s Hayabusa2 mission to Ryugu, a carbonaceous asteroid like Bennu, says NASA. Hayabusa2 found that Ryugu also lacks fine regolith and has high-porosity rocks, says the agency.
S-type asteroids are expected to have denser, less porous rocks than carbonaceous asteroids. By contrast, Cambioni and colleagues predict terrains rich in fine regolith to be common on S-type asteroids, the second-most populous type of asteroids observed in the solar system, says NASA. “We demonstrated the central role of rock porosity in driving the diversity of asteroid surfaces,” said Cambioni.