Lucy, which is on a mission to study asteroids in the Solar System, noticed another object orbiting the asteroid named Dinkinesh close to Earth in November 2023. Scientists think Selam is composed of material ejected from the surface of the rapidly spinning Dinkinesh.
Based on the relationship between these two objects in the Asteroid Belt between Mars and Jupiter, the researchers created a model to calculate Selam's age. Normally, the age of asteroids is calculated by looking at the number of impact craters on their surface. This method is based on the idea that the longer the asteroid remains in space, the more impacts it will receive, which will increase the number of craters.
The scientists who conducted the study, published in the peer-reviewed journal Astronomy and Astrophysics, analyzed the dynamics between the motions of Dinkinesh and Selam. Such binary systems are in a tug-of-war with the effects of gravity and solar radiation. These two effects, which also change the energy of the system, eventually come to equal power and the system reaches equilibrium.
"By solar system standards, the new walker is the age of a child"
Assuming this equilibrium was achieved, the research team tried to find out how long it would have taken Selam to reach this point after its formation.Using computer simulations and 1 million calculations, the scientists determined that the asteroid's age was around 3 million years. These results indicate that Selam is as young as a toddler by Solar System standards.
"Finding the age of asteroids is important for understanding them, and this asteroid is quite young relative to the age of the Solar System, meaning it formed recently," said Colby Merrill, a PhD student in Aerospace Engineering at Cornell University, who co-authored the study.
"It's an extraordinarily unique and complex object."
Merrill also notes that Selam is "an extraordinarily unique and complex object". The object consists of two lobes of rubble stuck together, and such an object, called a contact binary system, has never before been seen orbiting an asteroid.
The researchers believe that the method they used to calculate Selam's age could be applied to other binary asteroid systems to save money. It is estimated that about 15 percent of near-Earth asteroids have companions.
Lucy, whose next stop will be the asteroid 52246 Donaldjohanson between Mars and Jupiter, will then visit asteroids orbiting Jupiter. Launch into space on October 16, 2021
