Asteroid Dinkinesh's duo Selam spotted by NASA's Lucy spacecraft turns out to be cosmic toddler

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Generally, astronomers date an asteroid by counting the number of impact craters on its surface- the more the craters, the longer that an asteroid has been around to receive those impacts. But Merrill and his colleagues used a different method.

Last year in November, NASA's Lucy spacecraft on its mission to study asteroid Dinkinesh, found out that it is actually a binary. That little piece of rock hidden behind asteroid Dinkinesh or Dinky was named Selam by astronomers. Since then, experts have been studying the little moonlet for more information.

In one such study, they tried to estimate the age of Selam and found out that it is actually a toddler. According to their calculations, the tiny Selam which separated from its larger companion Dinky about 2 to 3 million years back is way younger than known.

"Finding the ages of asteroids is important to understanding them, and this one is remarkably young when compared to the age of the solar system, meaning it formed somewhat recently," Colby Merrill, a doctoral student at Cornell University, said in a statement. 

How astronomers found Selam is a toddler 

Merill and team have been investigating the newly found asteroid's dynamics and began constructing a model of how Selam orbits Dinkinesh. They found out that Selam orbits Dinkinesh in loosely packed debris ejected by the asteroid. Assuming that this is the origin of Selam, the team used a model to estimate the asteroid's age. 

Generally, astronomers date an asteroid by counting the number of impact craters on its surface- the more the craters, the longer an asteroid has been around to receive those impacts. But Merrill and his colleagues used a different method.

They simulated Selam forming from Dinkinesh under a range of different starting conditions and waited until Selam reached the orbit that Lucy glimpsed last November.

The team simulated 1 million scenarios that resulted in a Selam-like body forming. The median scenario dated Selam as 3 million years old, while the most common answer was closer to 2 million. "If either of these figures is correct, Selam may actually be younger than Lucy's namesake, the 3.2-million-year old human ancestor Australopithecus afarensis discovered in Ethiopia in the 1970s", concludes the team.

"Obtaining the age of this one body can help us to understand the population as a whole," Merrill further said.

The authors published their work in the journal Astronomy & Astrophysics on April 5.

For Lucy, it has only begun its tour of the solar system. The next asteroid on its itinerary, located between Mars and Jupiter, is 52246 Donaldjohanson, which Lucy will visit in 2025. 

(With inputs from agencies)

Riya Teotia

Riya is a sub-editor at WION and a passionate storyteller who creates impactful and detailed stories through her articles. She likes to write on defence tech