Astronomers say that asteroid Dinginesh’s lunar contact is binary

Dinginesh is a small asteroid orbiting the Sun near the inner edge of the main asteroid belt. NASA’s Lucy spacecraft recently revealed that the 720-m-diameter asteroid is unexpectedly complex: It has a prominent crater through an equatorial ridge and is now orbited by an interacting binary satellite named Selam. The satellite has two lobes of equal size with diameters of 210 m and 230 m. It is tidally locked around Dinginesh at a distance of 3.1 km with an orbital period of about 52.7 hours.

Stereographic image pairs (ac) taken by the L’LORRI instrument on NASA’s Lucy spacecraft on November 1, 2023, show asteroid Dinginesh. Yellow and pink dots represent trough and crest features, respectively. These images were sharpened and processed to increase contrast. Image (d) shows a side view of Dinginesh and its satellite cell taken a few minutes after approach. Image credit: NASA / GSFC / SwRI / Johns Hopkins APL / NOIRLab.

„We want to understand the dynamics of small bodies in our solar system because it’s critical to understanding how Earth-like planets got here,” said Lucy Principal Investigator Dr. Hal Levison, a researcher at Southwest Research Institute.

„Essentially, the planets formed when billions of tiny objects orbiting the Sun, asteroids, ran into each other.”

„How objects behave when they hit each other, whether they break or stick together, has a lot to do with their strength and internal structure.”

The researchers hypothesize that Dinginesh reveals its internal structure by how it responds to stress.

Spinning in sunlight over millions of years, small forces from thermal radiation emanating from the asteroid’s hot surface created a small torque that caused the dinginesh to spin progressively faster, creating centrifugal forces until part of the asteroid shifted into a more elongated shape. .

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This event probably caused the debris to enter a close orbit, which became the raw material that produced the ridge and the satellite.

If Dinginesh were very weak, like a liquid pile of sand, its particles would gradually drift equatorward and fly off into orbit as it spins rapidly.

However, the images suggest that it was stronger than a liquid, like a rock, able to hold together for a long time, eventually giving way to stress and fragmenting into larger pieces. Compared to most rocks on Earth, the amount of force required to fragment a small asteroid like Dinginesh is minimal.

„This crater is a sudden failure, and an earthquake, gradual stress and then sudden release, instead of a slow process like a sand dune,” said Lucy Project Scientist Dr. Keith Noll, NASA’s Goddard Space Explorer. Aviation center.

„These features tell us that Dinginesh has some strength, and they allow us to do a little historical reconstruction to see how this asteroid formed,” Dr Levison said.

„It broke up, and things moved during that failure, creating a disc of material, some of which rained back onto the surface to form ridges.”

„We think some of the material in the disk formed the lunar core, which is actually two objects touching each other, a configuration known as a contact binary. The details of how this unusual moon formed remain a mystery.

The Findings Published in the magazine Nature.


HF Levison and many others. 2024. Asteroid (152830) is a interacting binary satellite of Dinginesh. Nature 629, 1015-1020; Two: 10.1038/s41586-024-07378-0

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